1911 Encyclopædia Britannica/Sugar
SUGAR, in chemistry, the generic name for a certain series of carbohydrates, i.e. substances of the general formula Cn(H2O)m. Formerly the name was given to compounds having a sweet taste, e.g. sugar of lead, but it is now restricted to certain oxy-aldehydes and oxy-ketones, which occur in the vegetable and animal kingdoms either free or in combination as glucosides (q.v.) and to artificial preparations of similar chemical structure. Cane sugar has been known for many centuries; milk sugar was obtained by Fabrizio Bartoletti in 1615; and in the middle of the 18th century Marggraf found that the sugars yielded by the beet, carrot and other roots were identical with cane sugar. The sugars obtained from honey were investigated by Lowitz and Proust, and the latter decided on three species: (1) cane sugar, (2) grape sugar, and (3) fruit sugar; the first has the formula C12H22O11, the others C6H12O6. This list has been considerably developed by the discovery of natural as well as of synthetic sugars.
It is convenient to divide the sugars into two main groups: monosaccharoses (formerly glucoses) and disaccharoses (formerly saccharoses). The first term includes simple sugars containing two to nine atoms of carbon, which are known severally as bioses, trioses, tetroses, pentoses, hexoses, &c.; whilst those of the second group have the formula C12H22O11 and are characterized by yielding two monosaccharose molecules on hydrolysis. In addition trisaccharoses are known of the formula C18H32O16; these on hydrolysis yield one molecule of a monosaccharose and one of a disaccharose, or three of a monosaccharose. It is found also that some monosaccharoses behave as aldehydes whilst others contain a keto group; those having the first character are called aldoses, and the others ketoses. All sugars are colourless solids or syrups, which char on strong heating; they are soluble in water, forming sweet solutions but difficultly soluble in alcohol. Their solutions are optically active, i.e. they rotate the plane of polarized light; the amount of the rotation being dependent upon the concentration, temperature, and, in some cases, on the age of the solution (cf. Glucose). The rotation serves for the estimation of sugar solutions (saccharimetry). They are neutral to litmus and do not combine with dilute acids or bases; strong bases, such as lime and baryta, yield sac char ates, whilst, under certain conditions, acids and acid anhydrides may yield esters. Sugars are also liable to fermentation. Our knowledge of the chemical structure of the monosaccharosés may be regarded as dating from 1880, when Zincke suspected some to be ketone alcohols, for it was known that glucose and fructose, for example, yielded penta-acetates, and on reduction gave hexahydric alcohols, which, when reduced by hydriodic acid, gave normal and secondary hexyliodide. The facts suggested that the six carbon atoms formed a chain, and that a hydroxy group was attached to five of them, for it is very rare for two hydroxy groups to be attached to the same carbon atom. The remaining oxygen atom is aldehyde or ketonic, for the sugars combine with hydrocyanic acid, hydroxylamine and phenylhydrazine. The correctness of this view was settled by Kiliani in 1885. He prepared the cyanhydrins of glucose and fruotose, hydrolysed them to the corresponding oxy-acids, from which the hydroxy groups were split out by reduction; it was found that glucose yielded) normal heptylic acid and fructose methylbutylacetic acid; hence glucose is an aldehyde alcohol, CH2OH·(CH·OH)4·CHO, whilst fructose is a ketone alcohol CH2OH·(CH·OH)3·CO·CH2OH. Kiliani also showed that arabinose, C5H12O6, a sugar found in cherry gum, was an aldopentose, and thus indicated an extension of the idea of a “sugar.”
Before proceeding to the actual synthesis of the sugars, it is advisable to discuss their decompositions and transformations.
1. Cyanhydrins.—The cyanhydrins on hydrolysis give monocarboxylic acids, which yield lactones; these compounds when reduced by sodium amalgam in sulphuric acid solution yield a sugar containing one more carbon atom. This permits the formation of a higher from a lower sugar (E. Fischer)
2. Oximes.—The oximes permit the reverse change, Le. the passage from a higher to a lower sugar. Wohl forms the oxime and converts it into an acetylated nitrile by means of acetic anhydride and sodium acetate; ammoniacal silver nitrate solution removes hydrocyanic acid and the resulting acetate is hydrolysed by acting with ammonia to form an amide, which is finally decomposed with sulphuric acid.
Ruff effects the same change by oxidizing the sugar to the oxy-acid, and then further oxidizing this with Fenton's reagent, i.e. hydrogen peroxide and a trace of a ferrous salt:
3. Phenylhydrazine Derivatives.—Fischer found that if one molecule of phenylhydrazine acted upon one molecule of an aldose or ketose a hydrazone resulted which in most cases was very soluble in water, but if three molecules of the hydrazine reacted, (one of which is reduced to ammonia and aniline) insoluble crystalline substances resulted, termed osazones, which readily characterized the sugar from which it was obtained.
On warming the osazone with hydrochloric acid the phenylhydrazine residues are removed and an osone results, which on reduction with zinc and acetic acid gives a ketose.
A ketose may also be obtained by reducing the osazone with zinc and acetic to an osamine, which with nitrous acid gives the ketose:
These reactions permit the transformation of an aldose into a ketose; the reverse change can only be brought about by reducing the ketose to an alcohol, and oxidizing this compound to an aldehyde. It is seen that aldoses and ketoses which differ stereochemically in only the two final carbon atoms must yield the same osazone; and since d-mannose, d-glucose, and d-fructose do form the same osazone (d-glucosazone) differences either structural or stereochemical must be placed in the two final carbon atoms.
It may here be noticed that in the sugars there are asymmetric carbon atoms, and consequently optical isomers are to be expected. Thus glucose, containing four such atoms, can exist in 16 forms; and the realization of many of these isomers by E. Fischer may be regarded as one of the most brilliant achievements in modern chemistry. The general principles of stereochemistry being discussed in Stereoisomerism (q.v.), we proceed to the synthesis of glucose and fructose and then to the derivation of their configurations.
In 1861 Butlerow obtained a sugar-like substance, methylenitan, by digesting trioxymethylene, the solid polymer of formaldehyde, with lime. The work was repeated by O, Loew, who prepared in 1885 a sweet, unfermentable syrup, which he named formose, C5H17O6 and, later, by using magnesia instead of lime, he obtained the fermentable methose. Fischer showed that methose was identical with the α-acrose obtained by himself and Tafel in 1887 by decomposing acrolein dibromide with baryta, and subsequently prepared by oxidizing glycerin with bromine in alkaline solution, and treating the product with dilute alkali at 0°. Glycerin appears to yield, on mild oxidation, an aldehyde, CH2OH·CH(OH)·CHO, and a ketone, CH2OH·CO·CH2OH, and these condense as shown in the equation:
CH2OH·CH(OH) + CHO + CH2OH·CO·CH2OH =
CH2OH·CH(OH)·CH(OH)·CH(OH)·CO.CH2OH + H2O.
The osazone prepared from α-acrose resembled most closely the glucosazone yielded by glucose, mannose, and fructose, but it was optically inactive; also the ketose which it gave after treatment with hydrochloric acid and reduction of the osone was like ordinary fructose except that it was inactive. It was surmised that α-acrose was a mixture of dextro and laevo fructose, a supposition which was proved correct by an indirect method. The starting point was ordinary (d)mannite (mannitol), C6H14O6, a naturally occurring hexahydric alcohol, which only differed from a.-acritol, the alcohol obtained by reducing α-acrose, with regard to optical activity. Mannite on oxidation yields an aldose, mannose, C6,H12O6 which on further oxidation gives a mannonic acid, C5H8(OH)5·CO2H; this acid readily yields a lactone. Also Kiliani found. that the lactone derived from the cyanhydrin of natural arabinose (laevo) was identical with the previous lactone except that its rotation was equal and opposite. On mixing the eslactones and reducing (d + 1) mnanitol was obtained, identical with a-acritol. A separation of α-acrose was made by acting with beer yeast, which destroyed the ordinary fructose and left l-fructose which was isolated as its osazone. Also (d + l) mannonic acid can be split into the d and l acids by fractional crystallization of the strychnine or brucine salts. The acid yields, on appropriate treatment, d-mannose and d-mannite. Similarly the l acid yields the laevo derivatives.
The next step was to prepare glucose. This was effected indirectly. The identity of the formulae and osazones, of d-mannose and d-glucose showed that the stereochemical differences were situated at the carbon atom adjacent to the aldehyde group. Fischer applied a method indicated by Pasteur in converting dextro into laevo-tartaric acid; he found that both d-mannonic and d-gluconic acids (the latter is yielded by glucose on oxidation) were mutually convertible by heating with quinoline under pressure at 140°. It was then found that on reducing the lactone of the acid obtained from d-mannonic acid, ordinary glucose resulted.
Fischer's α-acrose therefore led to the synthesis of the, dextro and laevo forms of mannose, glucose and fructose; and these substances have been connected synthetically with many other sugars by means of his cyanhydrin process, leading to higher sugars, and Wohl and Ruff's processes, leading to lower sugars. Certain of these relations are here summarized (the starting substance is in italics):—
l-Glucose ← l-arabinose → l-mannose → l-mannoheptose; glucononose ← α-gluco-octose ← α-glucoheptose ← d-glucose → β~glucoheptose → β-gluco-octose;
d-mannose→d-mannoheptose→manno-octose→mannononose; d-glucose →d-arabinose→d-erythrose.
Their number is further increased by spatial inversion of the dicarboxylic acids formed on oxidation followed by reduction; for example: d- and l-glucose yield d- and l-gulose; and also, by Lobry de Bruyn and Van Ekenstein's discovery that hexoses are transformed into mixtures of their isomers when treated with alkalis, alkaline earths, lead oxide, &c.
Biose.—The only possible biose is glycollic aldehyde, CHO·CH2OH, obtained impure b Fischer from bromacetaldehyde and baryta water, and crystalline by Fenton by heating dihydroxymaleic acid with water to 60°. It polymerizes to a tetrose under the action of sodium hydroxide.
Trioses.-The trioses are the aldehyde and ketone mentioned above as oxidation products of glycerin. Glyceric aldehyde, CH2OH·CH(OH)·CHO, was obtained pure by Wohlon oxidizing acrolein acetal, CH2·CH(OC2H5)2, and hydrolysing. Although containing an asymmetric carbon atom it has not been resolved. The ketone, dihydroxyacetone, CH2OH·CO·CH2OH, was obtained by Piloty by condensing formaldehyde with nitromethane, reducing to a hydroxylamino compound, which is oxidized to the oxime of dihydroxyacetone; the ketone is liberated by oxidation with bromine water:
3H·CHO + CH3NO2 → (CH2OH)2C·N02 → (CH2OH)3C·NH OH
→ (CH2OH)2C: NOH → (CH2OH)2CO.
The ketone is also obtained when Bertrand's sorbose bacterium acts on glycerol; this medium also acts on other alcohols to yield ketoses; for exam le: erythrite gives erythrulose, arabite arabinulose, mannitol fructose, &c.
Tetroses.-Four active tetroses are possible, and three have been obtained by Ruff and Wohl from the pentoses. Thus Wohl prepared l-threose from l-xylose and l-erythrose from l-arabinose, and Ruff obtained d- and l-erythrose from d- and l-arabonic acids, the oxidation products of d- and l-arabinoses. Impure inactive forms result on the polymerization of glycollic aldehyde and also on the oxidation of erythrite, a tetrahydric alcohol found in some lichens. d-Erythrulose is a ketose of this series.
Pentoses.-Eight stereo isomeric pentaldoses are possible, and six are known: d- and l-arabinose, d- and l-xylose, l-ribose, and d-lyxose. Scheibler discovered l-arabinose in 1869, and regarded it as a glucose; in 1887 Kiliani proved it to be a pentose. d-Arabinose is obtained from d-glucose by Wohl's method l-Xylose was discovered by Koch in 1886; its enantiomorph is prepared from d-gulose by Wohl's. method. l-Ribose and d-lyxose are prepared by inversion from l-arabinose and l-xylose; the latter has also been obtained from d-galactose. We may notice that the entoses differ from other sugars by yielding furfurol when boiled with hydrochloric acid. Rhamnose or isodulcite, a component of certain glucosides, fucose, found combined in seaweeds and chinovose, present as its ethyl ester, chinovite, in varieties of quina-bark, are methyl pentoses. l-Arabinulose obtained from arabite and Bertrand's sorbium bacterium is a ketose.
Hexoses.-The hexoses may be regarded as the most important sub-division of the monosaccharoses. The reader is referred to Glucose and Fructose for an account of these substances. The next important aldose is mannose. d-Mannose, first prepared by oxidizing d-mannite, found in plants and manna-ash (Fraxinus ornus), was obtained by Tollens and Gans on hydrolysing cellulose and by Reis from seminine (reserve cellulose), found in certain plant seeds, e.g. vegetable ivory. l-Mannose is obtained from l-mannonic acid. Other forms are: d- and l-gulose, prepared from the lactones of the corresponding gulonic acids, which are obtained from d- and l-glucose by oxidation and inversion; d- and l-idose, obtained by inverting with pyridine d- and l-gulonic acids, and reducing the resulting idionic acids; d- and l-galactose, the first being obtained by hydrolysing milk sugar with dilute sulphuric acid, and the second by fermenting inactive galactose (from the reduction of the lactone of d, l-galactonic acid) with yeast; and d- and l-talose obtained by inverting the galactonic acids by pyridine into d- and l-talonic acids and reduction. Of the ketoses, we notice d-sorbose, found in the berries of mountain-ash, and d-tagatose, obtained by Lobry de Bruyn and van Ekenstein on treating galactose with dilute alkalis, talose and l-sorbose being formed at the same time. The higher sugars call for no special notice.
Configuration of the Hexaldosed—The plane projection of molecular structures which differ stereochemically is discussed under Stereo-isomerism; in this place it suffices to say that, since the terminal groups of the hexaldose molecule are different and four asymmetric carbon atoms are present, sixteen hexaldoses, are possible; and for the hexahydric alcohols which they yield on reduction, and the tetrahydric dicarboxylic acids which they give on oxidation, only ten forms are possible. Employing the notation in which the molecule is represented vertically with the aldehyde group at the bottom, and calling a carbon atom + or − according as the hydrogen atom is to the left or right, the possible configurations are shown in the diagram. The' grouping of the forms 5 to 10 with 11 to 16 is designed to show that the pairs 5, 11 for example become identical when the terminal groups are the same.
We can now proceed to the derivation of the structure of glucose. Since both d-glucose and d-gulose yield the same active (d) saccharic acid on oxidation, the configuration of this and the corresponding l-acid must be sought from among those numbered 5-10 in the above table. Nos. 7 and 8 can be at once ruled out, however, as acids so constituted would be optically inactive and the saccharic acids are active. If the configuration of d-saccharin acid were given by either 6 or 10, bearing in mind the relation of mannose to glucose, it would then be necessary to represent d-mannosaccharic acid by either 7 or 8—as the forms 6 and 10 pass into 7 and 8 on changing the sign of a terminal group; but this cannot be done as mannosaccharic acid is optically active. Nos. 6 and 10 must, in consequence, also be ruled out. No. 5, therefore, represents the configuration of one of the saccharic acids, and No. 9 that of the isomeride of equal opposite rotatory power. As there is no means of distinguishing between the configuration of a dextro- and laevo-modification, an arbitrary assumption must be made. No. 5 may therefore be assigned to the d- and No. 9 to the l-acid. It then follows that d-mannose is represented by No. 1, and l-mannose by No. 4, as mannose is produced by reversing the sign of the asymmetric system adjoining the terminal COH group.
It remains to distinguish between 5 and 11, 9 and 15 as representing glucose and gulose. To settle this point it is necessary to consider the configuration of the isomeric pentoses—arabinose and xylose—from which, they may be prepared. Arabinose being convertible into l-glucose and xylose into l-gulose, the alternative formulae to be considered are—
CH2(OH)− − − + COH
CH2(OH)+ + + − COH
CH2(OH) − − − COH
CH2(OH) + − − COH.
CO2H − 0 − C02H CO2H + 0 2 CO2H,
When xylose is combined with hydrocyanic acid and the cyanide is hydrolysed, together with l-gulonic acid, a second isomeric acid, ” l-idonic acid, is produced, which on reduction yields the hexaldose l-idose. When l-gulonic acid is heated with pyridine, it is converted into l-idonic acid, and vice versa; and d-gulonic acid may in a similar manner be converted into d-idonic acid, from which it is possible to prepare d-idose. It follows from the manner in which l-idose is produced that its configuration is CH2(OH)+ − − + COH.
The remaining aldohexoses discovered by Fischer are derived from d-galactose from milk-sugar. When oxidized this aldohexose is first converted into the monobasic galactonic acid, and then into dibasic mucic acid; the latter is optically inactive, so that its configuration must be one of those given in the sixth and seventh columns of the table. On reduction it yields an inactive mixture of galactonic acids, some molecules being attacked at one end, as it were, and an equal number of others at the other. On reducing the lactone prepared from the inactive acid an inactive galactose is obtained from which l-galactose may be separated by fermentation. Lastly, when d-galactonic acid is heated with pyridine, it is converted into talonic acid, which is reducible to talose, an isomeride l-caring to galactose the same relation that mannose bears to glucose. It can be shown that d-galactose is CH2(OH) + − + − COH, and hence d-talose is CH2(OH) + − + + COH.
The configurations of the penta- and tetra-aldoses have been determined by similar arguments; and those of the ketoses can be deduced from the aldoses.
The disaccharoses have the formula C12H22O11; and are characterized by yielding under suitable conditions two molecules of a hexose: C12H22O11 + H2O = C6H12O6 + C6H12O5. The hexoses so obtained are not necessarily identical: thus cane sugar yields d-glucose and d-fructose (invert sugar); milk sugar and melibiose give d-glucose and d-galactose, whilst maltose yields only glucose. Chemically they appear to be ether anhydrides of the hexoses, the union being effected by the aldehyde or alcohol groups, and in consequence they are related to the ethers of glucose and other hexoses, i.e. to the alkyl glucosides. Cane sugar has no reducing power and does not form an hydrazone or osazone; the other varieties, however, reduce Fehling’s solution and form hydra zones and osazones, behaving as aldoses, i.e. as containing the group ·CH(OH)·CHO. The relation of the disaccharoses to the α- and β-glucosides was established by E. F. Armstrong (Journ. Chem. Soc., 1903, 85, 1305), who showed that cane sugar and maltose were α-glucosides, and raffinose an α-glucoside of melibiose. These and other considerations have led to the proposal of an alkylen oxide formula for glucose, first proposed by Tollens; this view, which has been mainly developed by Armstrong and Fischer, has attained general acceptance free Glucose and Glucoside). Fischer has proposed formulae for the important disaccharoses, and in conjunction with Armstrong devised a method for determining how the molecule was built up, by forming the osone of the sugar and hydrolysing, whereupon the hexosone obtained indicates the aldose part of the molecule. Lactose is thus found to be glucosido-galactose and melibiose a galactosido-glucose.
Several disaccharoses have been synthesized. By acting with hydrochloric acid on glucose Fischer obtained isomaltose, a disaccharose very similar, to maltose but differing in being amorphous and unfermentable by yeast. Also Marchlewski (in 1899) synthesized cane sugar from potassium fructosate and acetochloroglucose; and after Fischer discovered that acetochlorohexoses readily resulted from the interaction of the hexose penta-acetates and liquid hydrogen chloride, several others have been obtained.
Cane sugar, saccharose or saccharobiose, is the most important sugar; its manufacture is treated below. When slowly crystallized it forms large monoclinic prisms which are readily soluble in water but difficulty soluble in alcohol. It melts at 160°, and on cooling solidifies to a glassy mass, which on standing gradually becomes opaque and crystalline. When heated to about 200° it yields a brown amorphous substance, named caramel, used in colouring liquors, &c. Concentrated sulphuric acid gives a black carbonaceous mass; boiling nitric acid oxidizes it to d-saccharic, tartaric and oxalic acids; and when heated to 160° with acetic anhydride an octa-acetyl ester is produced. Like glucose it gives saccharates with lime, baryta and strontia.
Milk sugar, lactose, lactobiose, C12H22O11, found in the milk of mammals, in the amniotic liquid of cows, and as a pathological secretion, is prepared by evaporating whey and purifying the sugar which separates by crystallization. It forms hard white rhombic prisms (with 1H2O), which become anhydrous at 140° and melt with decomposition at 205°. It reduces ammoniacal silver solutions in the cold, and alkaline copper solutions on boiling. Its aqueous solution has a faint sweet taste, and is dextro-rotatory, the rotation of a fresh solution being about twice that of an old one. It is difficultly fermented by yeast, but readily by the lactic acid bacillus. It is oxidized by nitric acid to d-sacchharic and mucic acids; and acetic anhydride gives an octa-acetate.
Maltose, malt-sugar, maltobiose, C12H22O11, is formed, together with dextrine, by the action of malt diastase on starch, and as an intermediate product in the decomposition of starch by sulphuric acid, and of glycogen by ferments. It forms hard crystalline crusts (with 1H2O) made up of hard white needles.Less important disaccharoses are: Trehalose or mycose, C12H22O11·2H2O, found in various fungi, e.g. Bolelus edulis, in the Oriental Trehala and in ergot of rye; melibiose, C12H22O11, formed, with fructose, on hydrolysing the trisaccharose melitose (or raffinose), C10H22O16·5H2O, which occurs in Australian manna and in the molasses of sugar manufacture; touranose, C12H22O11 formed with d-glucose and galactose on hydrolysing another trisaccharose, melizitose, C10H22O15·2H2O, which occurs in Pinus larix and in Persian manna; and agavose, C12H22O11, found in the stalks of Agave Americana. (X.)
Sugar-cane is a member of the grass family, known botanically as Saccharum officinarum, the succulent stems of which are the source of cane sugar. It is a tall perennial grass-like plant, giving off numerous erect stems 6 to 12 ft. or more in height from a thick solid jointed root-stock. The stems are solid and marked with numerous shining, polished, yellow, purple or striped joints, 3 in. or less in length, and about 1½ in. thick. They are unbranched and bear in the upper portion numerous long narrow grass-like leaves arranged in two rows; the leaf springs from a large sheath and has a more or less spreading blade 3 ft. in length or longer, and 3 in. or more wide. The small flowers or spikelets are borne in pairs on the ultimate branches of a much branched feathery plume-like terminal grey inflorescence, 2 ft. or more long. Production of flowers is uncertain under cultivation and seed is formed very rarely. The plant is readily propagated by cuttings, a piece of the stem bearing buds at its nodes will root rapidly when placed in sufficiently moist ground. The sugar-cane is widely cultivated in the tropics and some sub-tropical countries, but is not known as a wild plant. Its native country is unknown, but it probably originated in India or some parts of eastern tropical Asia where it has been cultivated from great antiquity and whence its cultivation spread westwards and eastwards. Alphonse de Candolle (Origin of Cultivated Plants, p. 158) points out that the epoch of its introduction into different countries agrees with the idea that its origin was in India, Cochin-China or the Malay Archipelago, and regards it as most probable that its primitive range extended from Bengal to Cochin-China. The sugar-cane was introduced by the Arabs in the middle ages into Egypt, Sicily and the south of Spain where it flourished until the abundance of sugar in the colonies caused its cultivation to be abandoned. Dorn Enrique, Infante of Portugal, surnamed the Navigator (1394-1460) transported it about 1420, from Cyprus and Sicily to Madeira, whence it was taken to the Canaries in 1503, and thence to Brazil and Hayti early in the 16th century, whence it spread to Mexico, Cuba, Guadeloupe and Martinique, and later to Bourbon. It was introduced into Barbadoes from Brazil in 1641, and was distributed from there to other West Indian islands. Though cultivated in sub-tropical countries such as Natal and the Southern states, of the Union, it is essentially tropical in its requirements and succeeds best in warm damp climates such as Cuba, British Guiana and Hawaii, and in India and Java in the Old World. The numerous cultivated varieties are distinguished mainly by the colour of the internodes, whether yellow, red or purple, or striped, and by the height of the culm. Apart from the sugar-cane and the beet, which are dealt with in detail below, a brief reference need only be made here to maple sugar, palm sugar and sorghum sugar.
Maple Sugar.—This is derived from the sap of the rock or sugar maple (Acer saccharmum), a large tree growing in Canada and the United States.
The sap is collected in spring, just before the foliage develops, and is procured by making a notch or boring a hole in the stem of the tree about 3 ft. from the ground. A tree may yield 3 gallons of juice a day and continue flowing for six weeks; but on an average on y about 4 lb of sugar are obtained from each tree, 4 to 6 gallons of sap giving 1 lb of sugar. The sap is purified and concentrated in a simple manner, the whole work being carried on by farmers, who themselves use much of the product for domestic and culinary purposes.
Palm Sugar.—That which comes into the European market as jaggery or khaur is obtained from the sap of several palms, the wild date (Phoenix sylvestris), the palmyra (Borassus flabellifer), the coco-nut (Cocos nucifera), the gomuti (Arenga saccharifera) and others. The principal source is Phoenix sylvestris, which is cultivated in a portion of the Ganges valley to the north of Calcutta. The trees are ready to yield sap when five years old; at eight years they are mature, and continue to give an annual supply till they reach thirty years. The collection of the sap (toddy) begins about the end of October and continues, during the cool season, till the middle of February. The sap is drawn off from the upper growing portion of the stem, and altogether an average tree will run in a season 350 lb of toddy, from which about 35 lb of raw sugar—jaggery—is made by simple and rude processes. Jaggery production is entirely in native hands, and the greater part of the amount made is consumed locally; it only occasionally reaches the European market.
Sorghum Sugar.—The stem of the Guinea corn or sorghum (Sorghum saccharatum) has long been known in China as a source of sugar. The sorghum is hardier than the sugar-cane; it comes to maturity in a season; and it retains its maximum sugar content a considerable time, giving opportunity for leisurely harvesting. The sugar is obtained by the same method as cane sugar.
Cane Sugar Manufacture.—The value of sugar-canes at a given plantation or central factory would at first sight appear Commercial Values of Sugar-canes. to vary directly as the amount of saccharine contained in the juice expressed from them varies, and if canes with juice indicating 9° Beaumé be made a basis of value or worth, say at 10s. per ton, then canes with juice indicating
|in degrees Beaumé||10°||9°||8°||7°||6°|
|and containing in
|would be worth per
But this is not an accurate statement of the commercial value of sugar-canes—that is, of their value for the production of sugar to the planter or manufacturer-because a properly equipped and balanced factory, capable of making 100 tons of sugar per day, for 100 days’ crop, from canes giving juice of 9° B., or say 10,000 tons of sugar, at an aggregate expenditure for manufacture (i.e. the annual cost of running the factory) of £3 per ton, or £30,000 per annum, will not be able to make as much sugar per day with canes giving juice of 8° B., and will make still less if they yield juice of only 6° B. In practice, the expenses of upkeep for the year and of manufacturing the crop remain the same whether the canes are rich or poor and whether the crop is good or bad, the power of the factory being limited by its power of evaporation. For example, a factory able to evaporate 622 tons of water in 24 hours could treat 1000 tons of canes yielding juice of 9° B., and make therefrom 100 tons of sugar in that time; but this same factory, if supplied with canes giving. juice of 6° B., c0uld not treat more than 935 tons of canes in 24 hours, and would only make therefrom 62.2 tons of sugar.
The following table may be useful to planters and central factory owners. It shows the comparative results of working with juice of the degrees of density mentioned above, under the conditions described, for one day of 24 hours, and the real value, as raw material for manufacture, of cane giving juice of 6° B. to 10° B., with their apparent value based solely on the percentage of sugar in the juice. The canes in each case are assumed to contain 88% of juice and 12% of fibre, and the extraction by milling to be 75% of the weight of canes—the evaporative power of the factory being equal to 622 tons per 24 hours. The factory expenses are taken at £30,000 per annum, or £3 per ton on a crop of 10,000 tons (the sugar to cost £8 per ton all told at the factory)—equivalent to £300 per day for the 100 working days of crop time.
Tons of canes
crushed per day
Tons of juice expressed
Tons of water
Tons of 1st Massecuite
Tons sugar of all
Total output of
sugar in 100
Total value of all
sugars per day
at £8, per ton
|£497, 6||£594, 4||£693, 6||£800||£912|
Less factory expenses
Leaves for canes
|£197, 6||£294, 4||£393, 6||£500||£612|
Real value of
canes per ton
Apparent value (see
But it is obvious that it would not pay a planter to sell canes at 45.2½d. a ton instead of at 10s. a ton, any more than it would pay a factory to make only 62.2 tons of sugar in 24 hours, or 6220 tons in the crop of 100 days, instead of 10,000 tons. Hence arises the imperative necessity of good cultivation by the planter, and of circumspection in the purchase and acceptance of canes on the part of the manufacturer.
The details of manufacture of sugar from canes and of sugar from beetroots differ, but there are five operations in the production of the sugar of commerce from either material which are common to both processes. These are:—
- 1. The extraction of the juice.
- 2. The purification or defecation of the juice.
- 3. The evaporation of the juice to syrup point.
- 4. The concentration and crystallization of the syrup.
- 5. The curing or preparation of the crystals for the market by separating the molasses from them.
Extraction of Juice.—The juice is extracted from canes by squeezing them between rollers. In India at the present day there are thousands of small mills worked by hand, through which Extraction by Pressure the peasant cultivators pass their canes two or three at a time, squeezing them a little, and, extracting perhaps a fourth of their weight in juice, from which they make a substance resembling a dirty sweetmeat rather than sugar. In Barbadoes there are still many estates making good Mascabado sugar; but as the juice is extracted from the canes by windmills, and then concentrated in open kettles heated by direct fire, the financial results are disastrous, since nearly half the yield obtainable from the canes is lost. In the best organized modern cane sugar estates as much as 12½% of the weight of the canes treated is obtained in crystal sugar of high polarizing power, although in Louisiana, where cultivation and manufacture are alike most carefully and admirably carried out, the yield in sugar is only about 7% of the weight of the canes, and sometimes, but seldom, as much as 9%. This is due to conditions of climate, which are much less favourable for the formation of saccharine in the canes than in Cuba. The protection afforded to the planters by their government, however, enables them to pursue the industry with considerable profit, notwithstanding the poor return for their labour in saleable produce. As an instance of the influence of climatic conditions combined with high cultivation the cane lands of the Sandwich Islands may be cited. Here the tropical heat is tempered by constant trade winds, there is perfect immunity from hurricanes, the soil is peculiarly suited for cane-growing, and by the use of specially-prepared fertilizers and an ample supply of water at command for irrigation the land yields from 50 to 90 tons of canes per acre, from which from 12 to 14% of sugar is produced. To secure this marvellous return, with an annual rainfall of 26 in., as much as 52,000,000 gallons of water are pumped per 24 hours from artesian wells on one estate alone. With an inexhaustible supply of irrigation water obtainable, there is no reason. why the lands in Upper Egypt, if scientifically cultivated and managed, should not yield as abundantly as those in the Sandwich Islands.
In the Paris Exhibition of 1900 a cane-crushing mill was shown with three rollers 32 in. in diameter by 60 in. long. It is driven by a powerful engine through triple gearing of 42 to 1, and speeded to have a surface velocity of rollers of 15 ft. 9 in. per minute. This mill is guaranteed to crush thoroughly and efficiently from 250 to 300 tons of canes in 24 hours. In Louisiana two mills, set one behind the other, each with three rollers 32 in. in diameter by 78 in. long, and driven by one engine through gearing of 15 to 1, are speeded to have a surface velocity of rollers of 25 ft. 6 in. per minute (or 60% more than that of the French mill described above), and they are efficiently crushing 900 to 1200 tons of canes in 24 hours. In Australia, Demerara, Cuba, Java and Peru double crushing and maceration (first used on a commercial scale in Demerara by the late Hon. William Russell) have been generally adopted; and in many places, especially in the Hawaiian Islands, triple crushing (i.e. passing the canes through three consecutive sets of rollers, in order to extract everything possible of extraction by pressure) is employed. In the south of Spain, in some favoured spots where sugar-canes can be grown, they are submitted even to four successive crushing.
It has been found in practice advantageous to prepare the canes for crushing in the mills, as above described, by passing them through a pair of preparing rolls which are grooved or indented in such manner as to draw in and flatten down the canes, no matter in which way they are thrown or heaped upon the cane-carrier, and thus prepare them for feeding the first mill of the series; thus the work of crushing is carried on uninterruptedly and without constant stoppages from the mills choking, as is often the case when the feed is heavy and the canes are not prepared.
Although it cannot be said that any one system of extraction is the best for all places, yet the following considerations are of general application—
- a. Whatever pressure be brought to bear upon it, the vegetable or woody fibre of crushed sugar-canes will hold and retain Yield from Crushing.for the moment a quantity of moisture equal to its own weigh t, and in practice 10% more than its own weight; or in other words, 100 lb of the best crushed megass will consist of 47–62 lb of fibre and 52–38 lb of moisture—that is, water with sugar in solution, or juice.
- b. Canes vary very much in respect of the quality and also as to the quantity of the juice they contain. The quantity of the juice is the test to which recourse must be had in judging the efficiency of the extraction, while the quality is the main factor to be taken into account with regard to the results of subsequent manufacture.
For the application of the foregoing considerations to practice, the subjoined table has been prepared. It shows the greatest quantity of juice that may be expressed from canes, according to the different proportions of fibre they contain, but without employing maceration or imbibition, to which processes reference is made hereafter. The percentages are percentages of the original weight of the uncrushed canes.
Percentage of fibre
Percentage of juice
Percentage of juice
retained in megass
Percentage of maximum
Percentage of maximum
Percentage of maximum
The British Guiana Planters’ Association appointed a sub-committee to report to the West India Commission on the manufacture of sugar, who stated the following:—
With canes containing 12% fibre the following percentages of sugar are extracted from the canes in the form of juice:—
Double crushing with 12% dilution
Triple crushing with 10% dilution
Diffusion with 25% dilution
These results are equivalent to
- 66–88% extraction for single crushing.
- 74–80% extraction„ for„ double crushing.
- 77–44% extraction„ for„ double crushing with 12% dilution
- 79–20% extraction„ for„ triple crushing„ with„ 10% dilution„
- 82–72% extraction„ for„ diffusion with with 25% dilution„
To prevent the serious loss of juice left in the megass by even the best double and triple crushing, maceration or imbibition was introduced. The megass coming from the first mill Maceration or Imbibition. was saturated with steam and water, in weight equal to between 20% and 30% and up to 40% of the original weight of the uncrushed canes. Consequently, after the last crushing the mixture retained by the residual megass was not juice, as was the case when crushing was employed without maceration, but juice mixed with water; and it was found that the loss in juice was reduced by one-half. A further saving of juice was sometimes possible if the market prices of sugar were such as to compensate for the cost of evaporating an increased quantity of added water, but a limit was imposed by the fact that water might be used in excess. Hence in the latest designs for large factories it has been proposed that as much normal juice as can be extracted by double crushing only shall be treated by itself, and that the megass shall then be soused with twice as much water as there is juice remaining in it; after which, on being subjected to a third crushing, it will yield a degraded juice, which would also be treated by itself. It is found that in reducing the juice of these two qualities to syrup, fit to pass to the vacuum pans for cooking to crystals, the total amount of evaporation from the degraded juice is about half that required from the normal juice produced by double crushing.
Great improvements have been made in the means of feeding the mills with canes by doing away with hand labour and substituting mechanical feeders or rakes, which by means of a Mechanical Improvements simple steam-driven mechanism will rake the canes from the cane waggons on to the cane-carriers. By the adoption of this system in one large plantation in the West Indies, crushing upwards of 1200 tons of canes per day, the labour of sixty-four hands was dispensed with, and was thus made available for employment in the fields. In Louisiana the use of mechanical feeders is almost universal.
With a view of safeguarding themselves from breakdowns caused by the inequality of feeding, or by the action of malicious persons introducing foreign substances, such as crowbars, bolts, &c., among the canes, and so into the mills, many planters have adopted so-called hydraulic attachments, applied either to the megass roll or the top roll bearings. These attachments, first invented by Jeremiah Howard, and described in the United States Patent Journal in 1858, are simply hydraulic rams fitted into the side or top caps of the mill, and pressing against the side or top brasses in such a manner as to allow the side or top roll to move away from the other rolls, while an accumulator, weighted to any desired extent, keeps a constant pressure on each of the rams. An objection to the top cap arrangement is, that if the volume or feed is large enough to lift the top roll from the cane roll, it will simultaneously lift it from the megass roll, so that the megass will not be as well pressed as it ought to be; and an objection to the side cap arrangement on the megass roll as well as to the top cap arrangement is, that in case more canes are fed in at one end of the rolls than at the other, the roll will be pushed out farther at one end than at the other; and though it may thus avoid a breakdown of the rolls, it is apt, in so doing, to break the ends off the teeth of the crown wheels by putting them out of line with one another. The toggle-joint attachment, which is an extremely ingenious way of attaining the same end as the hydraulic attachments, is open to the same objections.
Extraction of cane juice by diffusion (a process more fully described under the head of beetroot sugar manufacture) is adopted in a few plantations in Java and Cuba, in Louisiana Extraction by Diffusion. and the Hawaiian Islands, and in one or two factories in Egypt; but hitherto, except under exceptional conditions (as at Aska, in the Madras Presidency, where the local price for sugar is three or four times the London price), it would not seem to offer any substantial advantage over double or triple crushing. With the latter system practically as much sugar is obtained from the canes as by diffusion, and the resulting megass furnishes, in a well-appointed factory, sufficient fuel for the crop. With diffusion, however, in addition to the strict scientific control necessary to secure the benefits of the process, fuel—that is, coal or wood—has to be provided for the working off of the crop, since the spent chips or slices from the diffusers are useless for this purpose; although it is true that in some plantations the spent chips have to a certain extent been utilized as fuel by mixing them with a portion of the molasses, which otherwise would have been sold or converted into rum. The best results from extraction by diffusion have been obtained in Java, where there is an abundance of clear, good water; but in the Hawaiian Islands, and in Cuba and Demerara, diffusion has been abandoned on several well mounted estates and replaced by double and triple crushing; and it is not likely to be resorted to again, as the extra cost of working is not compensated by the slight increase of sugar produced. In Louisiana diffusion is successfully worked on two or three large estates; but the general body of planters are shy of using it, although there is no lack of water, the Mississippi being near at hand.
Purification.—The second operation is the coagulation of the albumen, and the separation of it with other impurities from the juice which holds them in suspension or solution. The moment the juice is expelled from the cells of the canes chemical inversion commences, and the sooner it is stopped the better. This is effected by the addition of lime to neutralize the free acid. As cold juice has a greater affinity for lime than hot juice, it is best to treat the juice with lime when cold. This is easily done in liming or measuring tanks of known capacity into which the juice is run from the mill. The requisite amount of milk of lime set up at 10° Beaumé is then added. Cream of lime of 17° Beaumé is sometimes used, but the weaker solution is preferable, since the proper proportion is more easily adjusted. In Demerara and other places the juice is then heated under pressure up to 220°F. to 250°F. for a few moments, on its way to a steam and juice separator, where the steam due to the superheated juice flashes off, and is either utilized for aiding Subsiding Tanks.the steam supplied to the multiple effect evaporators, ranks or or eating co juice on its way to the main, heater or it is allowed to escape into the atmosphere. The boiling juice is run down into subsiding tanks, where it cools, and at the same time the albumen, which has been suddenly coagulated by momentary exposure to high temperature, falls to the bottom of, the tank, carrying with it the vegetable and other matters which were in suspension in the juice. After reposing some time, the clear juice is carefully decanted by means of a pipe fixed by a swivel joint to an outlet in the bottom of the tank, the upper end of the pipe being always kept at the surface of the liquor by a float attached to it. Thus clear liquor alone is run off, and the mud and cloudy liquor at the bottom of the tank are left undisturbed, and discharged separately as required.
In Australia a continuous juice separator is generally used, and preferred to ordinary subsiding or filtering tanks. It is a cylindrical Continuous Juice Separator.vessel about 6 ft. deep, fitted with a conical bottom of about the same depth. Such a vessel is conveniently made of a diameter which will give the cylindrical portion sufficient capacity to hold the juice expressed from the cane-mill in one hour. The hot liquor is conducted downwards' in a continuous steady stream by a central pipe to eight horizontal branches, from which it issues into the separator at the level of the junction of the cylindrical and conical portions of the vessel. Since the specific gravity of hot liquor is less than that of cold liquor and since the specific gravity of the scum and particles of solid matter in suspension varies so slightly with the temperature that practically it remains constant, the hot liquor rises to the top of the vessel, and the scums and particles of solid matter in suspension separate themselves from it and fall to the bottom. By the mode of admission the hot liquor at its entry is distributed over a large area relatively to its volume, and while this is necessarily effected with but little disturbance to the contents of the vessel, a very slow velocity is ensured for the current of ascending juice. In a continuous separator of which the cylindrical portion measures 13 ft. in diameter and 6 ft. deep (a suitable size for treating a juice supply of 4000 to 4500 gallons per hour), the upward current will have a velocity of about 1 inch per minute, and it is found that all the impurities have thus ample time to separate themselves. The clear juice when it arrives at the top of the separator flows slowly over the level edges of, a cross canal and passes in a continuous stream to the service tanks of the evaporators or vacuum pan. The sloping sides of the conical bottom can be freed from the coating of scum which forms upon them every two or three hours by two rotatory scrapers, formed of L-irons, which can be slowly turned by an attendant by means of a central shaft provided with a suitable handle. The scums then settle down to the bottom of the cone, whence they are run off to the scum tank. Every twenty-four hours or so the flow of juice may be conveniently stopped, and, after all the impurities have subsided, the superincumbent clear liquor may be decanted by a cock placed, at the side of the cone for the purpose, and the vessel may be washed out. These separators are carefully protected by non-conducting cement and wood lagging, and are closed at the top to prevent loss of heat; and they will run for many hours without requiring to be changed, the duration of the run depending on the quality of the liquor treated and amount of impurities therein. Smaller separators of the same construction are used for the treatment of syrup.
In Cuba, Martinique, Peru and elsewhere the old-fashioned double-bottomed defector is used, into which the juice is run Double-bottomed Defectors.direct, and there limed and heated. This defector is made with a hemispherical copper bottom, placed in an outer cast-iron casing, which forms a steam jacket, and is fitted with a cylindrical curb or breast above the bottom. If double-bottomed defectors are used in sufficient number to allow an hour and a half to two hours for making each defecation, and if they are of a size which permits any one of them to be filled up by the cane-mill with juice in ten to twelve minutes, they will make as perfect a defecation as is obtainable by any known system; but their employment involves the expenditure of much high-pressure steam (as exhaust steam will not heat the juice quickly enough through the small surface of the hemispherical inner bottom), and also the use of filter presses for treating the scums. A great deal of skilled superintendence is also required, and first cost is comparatively large. When a sufficient number are not available for a two hours' defecation, it is the practice in some factories to skim off the scums that rise to the top, and then boil up the juice for a few minutes and skim again, and, after repeating the operation once or twice, to run off the juice to, separators or subsiders of any of the kinds previously described. In Java and Mauritius, where very clean canes are grown, double-bottomed defectors are generally used, and to them, perhaps as much as to the quality of the canes, may be attributed the very strong, fine sugars made in those islands. They are also employed in Egypt, being remnants of the plant used in the days when the juice passed through bone-black before going to the evaporators.
A modification of the system of double-bottom defectors has lately been introduced with considerable success in San Domingo and in Cuba, by which continuous and steady dischargeContinuous Defecation. of clear defecated juice is obtained on the one hand, and on the other a comparatively hard dry cake of scum or cachaza, and without the use of filter presses. These results are brought about by adding to the cold juice as it comes from the mill the proper proportion of milk of lime set up at 8° B., and then delivering the limed juice in a constant steady stream as near the bottom of the defector as possible; it is thus brought into immediate contact with the heating surface and heated once for all before it ascends, with the result of avoiding the disturbance caused in the ordinary defector by pouring cold juice from above on to the surface of the heated juice, and so establishing down-currents of cold juice and up-currents of hot juice. In the centre of the defector an open-topped cylindrical vessel is placed, with its bottom about 6 in. above the bottom of the defector and its top about 12 in. below the top of the defector. In this vessel is placed the short leg of a draw-off siphon, reaching to nearly the bottom. The action of the moderate heat, 210° F., on the limed juice causes the albumen in it to coagulate; this rising to the surface collects the cachazas, which form and float thereon. The clear juice in the meantime flows over the edge of the cylindrical vessel without disturbance and finds its way out by the short leg of the siphon, and so passes to the canal for collecting the defecated juice. The admission of steam must be regulated with the greatest nicety, so as to maintain an equable temperature, 208° to 210° F., hot enough to act upon the albumen and yet not enough to cause ebullition or disturbance in the juice, and so prevent a proper separation of the cachazas. This is attained by the aid of a copper pipe, 4 in. in diameter, which follows the curve of the hemispherical bottom, and is fitted from one side to the other of the defector, one end is entirely closed, and the other is connected by a small pipe to a shallow circular vessel outside the defector, covered with an india-rubber diaphragm, to the centre of which is attached a light rod actuating a steam throttle-valve, and capable of being adjusted as to length, &c. The copper pipe and circular vessel are filled with cold water, which on becoming heated by the surrounding juice expands, and so forces up the india-rubber diaphragm and shuts off the steam. By adjusting the length of the connecting rod and the amount of water. in the vessel, the amount of steam admitted can be regulated to a nicety. To make this apparatus more perfectly automatic, an arrangement for continually adding to and mixing with the juice the proper proportion of milk of lime has been adapted to it; and although it may be objected that once the proportion has been determined no allowance is made for the variation in the quality of the juice coming from the mill owing to the variations that may occur in the canes fed into the mills, it is obviously as easy to vary the proportion with the automatic arrangement from time to time as it is to vary in each separate direction, if the man in charge will take the trouble to do so, which he very seldom does with the ordinary defectors, satisfying himself with testing the juice once or twice in a watch. The scums forming on the top of the continuous defector become so hard and dry that they have to be removed from time to time with a specially constructed instrument like a flat spade with three flat prongs in front. These scums are not worth passing through the filter presses, and are sent to the fields direct as manure.
The scums separated from the juice by ordinary defecation entangle and carry away with them a certain amount of the juice with its contained saccharine. In some factories theyTreatment of the Scums are collected in suitable tanks, and steam is blown into them, which further coagulates the albuminous particles. These in their upward passage to the top, where they float, free themselves from the juice, which they leave below them comparatively clear. The juice is then drawn off and pumped up to one of the double-bottomed defectors and redefecated, or, where juice-heaters have been used instead of defectors, the scums from the separators or subsiders are heated and forced through filter presses, the juice expressed going to the evaporators and the scum cakes formed in the filter presses to the fields as manure.
In diffusion plants the milk of lime is added, in proper proportion, in the cells of the diffusion battery, and the chips or slices themselves act as a mechanical filter for the juice; while in the Sandwich Islands coral-sand filters have been employed for some years, in addition to the chips, to free the juice from impurities held in mechanical suspension. In Germany very similar filters have also been used, pearl-quartz gravel taking the place of coral sand, which it closely resembles. In Mexico filters filled with dry powdered megass have been found very efficient for removing the large quantity of impurities contained in the juice expressed from the very vigorous but rank canes grown in that wonderfully fertile country, but unless constant care is taken in managing them, and in changing them at the proper time, there is great risk of inversion taking place, with consequent loss of sugar.
After the juice has been defecated or purified by any of the means above mentioned it is sent to the evaporating apparatus, hereinafter described, where it is concentrated to 26° or 28° Beaumé, and is then conducted in a continuous stream either into the service tanks of the vacuum pan, if dark sugars are required, or, if a better colour is wanted, into clarifies. The latter are circular or rectangular vessels, holding from 500 to 1500 gallons each, according to the capacity of the factory, and fitted with steam coils at the bottom and skimming troughs at the top. In them the syrup is quickly brought up to the boil and skimmed for about five minutes, when it is run off to the service tanks of the vacuum pans. The heat at which the syrup boils in the clarifies, 220° F., has the property of separating a great deal of the gum still remaining in it, and thus cleansing the solution of sugar and water for crystallization in the vacuum pans; and if after skimming the syrup is run into separators or subsiders of any description, and allowed to settle down and cool before being drawn into the vacuum pan for crystallization, this cleansing process will be more thorough and the quality of the final product will be improved. Whether the improvement will be profitable or not to the planter or manufacturer depends on the market for the sugar, and on the conditions of foreign tariffs, which are not infrequently hostile.
Evaporation of the Juice to Syrup.-The third operation is the concentration of the approximately pure, but thin and watery, juice to syrup point, by driving off a portion of the water in vapour through some system of heating and evaporation. Since on an average 70% by measurement of the normal defecated cane juice has to be evaporated in order to reduce it to syrup ready for final concentration and crystallization in the vacuum pan, and since to attain the same end as much as 90 to 95% of the volume of mixed juices has to be evaporated when maceration or imbibition, is employed, it is clear that some more economical mode of evaporation is necessary in large estates than the open-fire batteries still common in Barbados and some of the West Indian islands, and in small haciendas in Central America and Brazil, but seldom seen elsewhere. With open-fire batteries for making the syrup, which was afterwards finished in the vacuum pan, very good sugar was produced, but at a cost that would be ruinous in to-day’s markets.
In the best days of the so-called Jamaica Trains in Demerara, three-quarters of a ton of coal in addition to the megass was burned per ton of sugar made, and with this for many years planters were content, because they pointed to the fact that in the central factories, then working in Martinique and Guadeloupe, with charcoal filters and triple-effect evaporation, 750 kilos of coal in addition to the megass were consumed to make 1000 kilos of sugar. All this has now been changed. It is unquestionably better and easier to evaporate in vacuo than in an open pan, and with a better system of firing, a more liberal provision of steam generators, and multiple-effect evaporators of improved construction, a far larger yield of sugar is obtained from the juice than was possible of attainment in those days, and the megass often suffices as fuel for the crop.
The multiple-effect evaporator, originally invented and constructed by Norberto Rilleux in New Orleans in 1840, has undergone Multiple-Effect Evaporators.many changes in design and construction since that year. The growing demand for this system of evaporation for application in many other industries besides that of sugar has brought to the front a large number of inventors. Forgetful or ignorant of the great principle announced and established by Rilleux, they have mostly devoted their energies and ingenuity to contriving all sorts of complicated arrangements to give the juice the density required, by passing and repassing it over the heating surface of the apparatus, the saving of a few square feet of which would seem to have been their main object. In some instances the result has been an additional and unnecessary expenditure of high-pressure steam, and in all the well-known fact—of the highest importance in this connexion—appears to have been disregarded, that the shorter the time the juice is exposed to heat the less inversion will take place in it, and therefore the less will be the loss of sugar. But this competition among inventors, whatever the incentive, has not been without benefit, because to-day, by means of very simple improvements in details, such as the addition of circulatory and increased area of connexions, what may be taken to be the standard type of multiple-effect evaporator (that is to say, vertical vacuum pans fitted with vertical heating tubes, through which passes the liquor to be treated, and outside of which the steam or vapour circulates) evaporates nearly double the quantity of water per square foot of heating surface per hour which was evaporated by apparatus in use so recently as 1885—and this without any increase in the steam pressure. That evaporation in vacuo, in a multiple-effect evaporator, is advantageous by reason of the increased amount of sugar obtained from a given quantity of juice, and by reason of economy of fuel, there is no doubt, but whether such, an apparatus should be of double, triple, quadruple or quintuple effect will depend very much on the amount of juice to be treated per day, and the cost of fuel. Thus, supposing that 1000 lb of coal were required to work a single vacuum pan, evaporating, say, 6000 lb of water in a given time, then 500 lb of coal would be required for a double-effect apparatus to do the same work, 333 lb for a triple effect, 250 for a quadruple effect, and 200 lb for a quintuple effect. In some places where coal costs 60s. a ton, and where steam is raised by coal, as in a beetroot factory it might pay to adopt a quintuple-effect apparatus, but on a cane-sugar estate, where the steam necessary for the evaporator is raised by burning the megass as fuel, and is first used in the engines working the mills, the exhaust alone passing to the evaporator, there would be very little, if any, advantage in employing a quadruple effect instead of a triple effect, and practically none at all in having a quintuple-effect apparatus, for the interest and sinking fund on the extra cost would more than counterbalance the saving in fuel.
With the juice of some canes considerable difficulty is encountered in keeping the heating surfaces of the evaporators clean and free from incrustations, and cleaning by the use of acid has to be resorted to. In places where work is carried on day and night throughout the week, the standard type of evaporator lends itself more readily to cleaning operations than any other. It is obviously easier to brush out and clean vertical tubes open at both ends, and about 6 ft. long, on which the scale has already been loosened by the aid of boiling with dilute muriatic acid or a weak solution of caustic soda in water, than it is to clean either the inside or the outside of horizontal tubes more than double the length. This consideration should be carefully remembered in the future by the planter who may require an evaporator and by the engineer who may be called upon to design or construct it, and more especially by a constructor without practical experience of the working of his constructions.
Concentration and Crystallization.—The defecated cane juice, having lost about 70% of its bulk by evaporation in the multiple effect evaporator, is now syrup, and ready to enter theHoward’s Vacuum Pan. vacuum pan for further concentration and crystallization. In a patent (No. 3607, 1815) granted to E. C. Howard it is stated, among other things, that “water dissolves the most uncrystallizable in preference to that most-crystallizable sugar,” and the patentee speaks of “a discovery I have made that no solution, unless highly concentrated, of sugar in water can without material injury to its colouring and crystallizing power, or to both, be exposed to its boiling temperature during the period required to evaporate such solution to the crystallizing point.” He stated that “he had made a magma of sugar and water at atmospheric temperature, and heated the same to 190° or 200° F. in a water or steam bath, and then added more sugar or a thinner magma, and the whole being then in a state of imperfect fluidity, but so as to close readily behind the stirrer, was filled into moulds and purged” (drained). “I do further declare,” he added, “that although in the application of heat to the refining of sugar in my said invention or process I have stated and mentioned the temperature of about 200 F. scale as the heat most proper to be used and applied in order to secure and preserve the colour and crystallizability of the sugars, and most easily to be obtained with precision and uniformity by means of the water bath and steam bath, yet when circumstances or choice may render the same desirable I do make use of higher temperatures, although less beneficial.” Howard at any rate saw clearly what was one of the indispensable requisites for the economical manufacture of fine crystal sugar of good colour—the treatment of saccharine solutions at temperatures very considerably lower than 212° F., which is the temperature of water boiling at normal atmospheric pressure. Nor was he long in providing means for securing these lower temperatures. His patent (No. 3754 of 1813) describes the closed vacuum pan and the air pump with condenser for steam by injection, the use of a thermometer immersed in the solution in the pan, and a method of ascertaining the density of the solution with a proof stick, and by observations of the temperature at which, while fluid and not containing grain, it could be kept boiling under different pressures shown by a vacuum gauge. A table is also given of boiling, points from 115° F. to 175° F., corresponding to decimal parts of an inch of mercury of the vacuum gauge. Since Howard published his invention the vacuum pan has been greatly improved and altered in shape and power, and especially of recent years, and the advantages of concentrating in vacuo having been acknowledged, the system has been adopted in many other industries, and crowds of inventors have turned their attention to the principle. In endeavouring to make a pan of less power do as much and as good work as one of greater power, they have imagined many ingenious mechanical contrivances, such as currents produced mechanically to promote evaporation and crystallization, feeding the pan from many points in order to spread the feed equally throughout the mass of sugar being cooked, and so on. All their endeavours have obtained at best but a doubtful success, for they have overlooked the fact that to evaporate a given weight of water from the syrup in a vacuum pan at least an equal weight (or in practice about 15% more) of steam must be condensed, and the first cost of mechanical agitators together with the expenditure they involve for motive power and maintenance, must be put against the slight saving in the heating surface effected by their employment. On the other hand, the advocates of admitting the feed into a vacuum pan in many minute streams appeal rather to the ignorant and incompetent sugar-boiler than to a man who, knowing his business thoroughly, will boil 150 tons of hot raw sugar in a pan in a few hours, feeding it through a single pipe and valve 10 in. in diameter. Nevertheless, it has been found in practice, when syrups with low quotient of purity and high quotient of impurity are being treated, injecting the feed at a number of different points in the pan does reduce the time required to boil the pan, though of no practical advantage with syrups of high quotient of purity and free from the viscosity which impedes circulation and therefore quick boiling. Watt, when he invented the steam engine, laid down the principles on which it is based, and they hold good to the present day. So also the principles laid down by Howard with respect to the vacuum pan hold good to-day: larger pans have been made and their heating surface as been increased, but it has been found by practice now, as it was found then, that an ordinary worm or coil 4 in. in diameter and 50 ft. long will be far more efficient per square foot of surface than a similar coil 100 ft. long. Thus the most efficient vacuum pans of the present day are those which have their coils so arranged that no portion of them exceeds 50 or 60 ft. in length; with such coils, and a sufficient annular space in the pan free from obstruction, in order to allow a natural down-current of the cooking mass, while an up-current all round is also naturally produced by the action of the heated worms or coils, rapid evaporation and crystallization can be obtained, without any mechanical adjuncts to require attention or afford excuse for negligence.
The choice of the size of the crystals to be produced in a given pan depends upon the market for which they are intended. It is of course presupposed that the juice has been properly defecated, because without this no amount of skill and knowledge in cooking in the pan will avail; the sugar resulting must be bad, either in colour or grain, or both, and certainly in polarizing power. If a very large firm grain like sugar-candy is required the syrup when first brought into the pan must be of low density, say 20° to 21° Beaumé, but if a smaller grain be wanted it can easily be obtained from syrup of 27° to 28° Beaumé. On some plantations making sugar for particular markets and use in refineries it is the custom to make only one class of sugar, by boiling the molasses produced by the purging of one strike with the sugar in the next strike. On other estates the second sugars, or sugars produced from boiling molasses alone, are not purged to dryness, but when sufficiently separated from their mother-liquor are mixed with the defecated juice, thereby increasing its saccharine richness, and after being converted into syrup in the usual manner are treated in the vacuum pan as first sugars, which in fact they really are.
In certain districts, notably in the Straits Settlements, syrup is prepared as described above for crystallization in a vacuum pan, but instead of being cooked in vacuo it is slowly boiled up in open double-bottom pans. These pans are sometimes heated by boiling oil, with the idea that under such conditions the sugar which is kept stirred all the time as it thickens cannot be burnt or caramelized; but the same object can be attained more economically with steam of a given pressure by utilizing its latent heat. The sugar thus produced, by constant stirring and evaporation almost to dryness, forms a species of small-grained concrete. It is called “basket sugar,” and meets with a brisk sale, at remunerative prices, among the Chinese coolies; and as the sugar as soon as cooled is packed ready for market, without losing any weight by draining, this branch of sugar-making is a most lucrative one whereever there is sufficient local demand. Very similar kinds of sugar are also produced for local consumption in Central America and in Mexico, under the names of “Panela” and “Chancaca,” but in those countries the sugar is generally boiled in pans placed over special fire-places, and the factories making it are on a comparatively small scale, whereas in the Straits Settlements the “basket sugar” factories are of considerable importance, and are fitted with the most approved machinery.
Curing or Preparation of Crystals for the Market.—The crystallized sugar from the vacuum pan has now to be separated from the molasses or mother-liquor surrounding the crystals. In some parts of Mexico and Central America this separation is still effected by running the sugar into conical moulds, and placing on the top a layer of moist clay or earth which has been kneaded in a mill into a stiff paste. The moisture from the clay, percolating through the mass of sugar, washes away the adhering molasses and leaves the crystals comparatively free and clear. It may be noted that sugar that will not purge easily and freely with clay will not purge easily and freely in centrifugal. But for all practical purposes the system of claying sugar is a thing of the past, and the bulk of the sugar of commerce is now purged in centrifugal, as indeed it has been for many years. The reason is obvious. The claying system involved the expense of large curing houses and the employment of many hands, and forty days at least were required for completing the operation and making the sugar fit for the market, whereas with centrifugal sugar cooked to-day can go to market to-morrow, and the labour employed is reduced to a minimum.
When Cuba was the chief sugar-producing country making clayed sugars it was the custom (followed in refineries and found advantageous in general practice) to discharge the strike of crystallized sugar from the vacuum pan into a receiver heated below by steam, and to stir the mass for a certain time, and then distribute it into the moulds in which it was afterwards clayed. When centrifugal were adopted for purging the whole crop (they had long been used for curing the second or third sugars), the system then obtaining of running the sugar into wagons or coolers, which was necessary for the second and third sugars cooked only to string point, was continued, but latterly “crystallization in movement,” a development of the system which forty years ago or more existed in refineries and in Cuba, has come into general use, and with great advantage, especially where proprietors have been able to erect appropriate buildings and machinery for carrying out the system efficiently. The vacuum pan is erected at a height which commands the crystallizers, each of which will, as in days gone by in Cuba, hold the contents of the pan, and these in their turn are set high enough to allow the charge to fall into the feeding-trough of the centrifugal, thus obviating the necessity of any labour to remove the raw sugar from the time it leaves the vacuum pan to the time it falls into the centrifugals. For this reason alone, and without taking into consideration any increase in the yield of sugar brought about by “crystallization in movement,” the system is worthy of adoption in all sugar factories making crystal sugar.
The crystallizers are long, horizontal, cylindrical or semi-cylindrical vessels, fitted with a strong horizontal shaft running from end to end, which is kept slowly revolving. The shaft Crystallizers. carries arms and blades fixed in such a manner that the mass of sugar is quietly but thoroughly moved, while at the same time a gentle but sustained evaporation is produced by the continuous exposure of successive portions of the mass to the action of the atmosphere. Thus also the crystals already formed come in contact with fresh mother-liquor, and so go on adding to their size. Some crystallizers are made entirely cylindrical, and are connected to the condenser of the vacuum pan; in order to maintain a partial vacuum in them, some are fitted with cold-water pipes to cool them and with steam pipes to heat them, and some are left open to the atmosphere at the top. But the efficiency of all depends on the process of almost imperceptible yet continuous evaporation and the methodical addition of syrup, and not on the idiosyncrasies of the experts who manage them; and there is no doubt that in large commercial processes of manufacture the simpler the apparatus used for obtaining a desired result, and the more easily it is understood, the better it will be for the manufacturer. The sugar made from the first syrups does not require a crystallizer in movement to prepare it for purging in the centrifugal, but it is convenient to run the strike into the crystallizer and so empty the pan at once and leave it ready to commence another strike, while the second sugars will be better for twenty-four hours’ stirring and the third sugars for forty-eight hours’ stirring before going to the centrifugals. To drive these machines electricity has been applied, with indifferent success, but they have been very efficiently driven, each independently of the others in the set, by means of a modification of a Pelton wheel, supplied with water under pressure from a pumping engine. A comparatively small stream strikes the wheel with a pressure equivalent to a great head, say 300 ft., and as the quantity of water and number of jets striking the wheel can be regulated with the greatest ease and nicety, each machine can without danger be quickly brought up to its full speed when purging high-class sugars, or allowed to run slowly when purging low-class sugars, until the heavy, gummy molasses have been expelled; and it can then be brought up to its full speed for finally drying the sugar in the basket, a boon which all practical sugar-makers will appreciate. The water forced by the force-pump against the Pelton wheels returns by a waste-pipe to the tank, from which the force-pump takes it again.
Recent Progress.—The manufacture of cane sugar has largely increased in volume since the year 1901–1902. This, apart from the effect of the abolition of the sugar bounties, has been mainly the result of the increased employment of improved processes, carried on in improved apparatus, under skilled supervision, and with due regard to the importance of the chemical aspects of the work.
Numerous central factories have been erected in several countries with plant of large capacity, and many of them work day and night for six days in the week. There were 173 of these Central Factories factories working in Cuba in 1908–1909, among which the “Chaparra,” in the province of Oriente, turned out upwards of 69,000 tons of sugar in the crop of about 20 weeks, and the “Boston” had an output of about 61,000 tons in the same time. Of the 178 factories at work in Java in 1908–1909, nearly all had most efficient plant for treating the excellent canes grown in that favoured island. (See Jaarboek voor suikerfabrikanten op Java, 13° Jaargang 1908–1909, pp. 22–61 Amsterdam, J. H. de Bussy.) The severance of the agricultural work, i.e. cane-growing, from the manufacturing work, sugar-making, must obviously conduce to better and more profitable work of both kinds.
The use of multiple-effect evaporation made it possible to raise the steam for all the work required to be done in a well-equipped Green Bagasse as Fuel.factory, making crystals, under skilful management, by means of the bagasse alone proceeding from the canes ground, without the aid of other fuel. The bagasse so used is now commonly taken straight from the cane mill to furnaces specially designed, for burning it, in its moist state and without previous drying, and delivering the hot gases from it to suitable boilers, such as those of the multitubular type or of the water-tube type. The value of fresh bagasse, or as it is often called “green” bagasse, as fuel varies with the kind of canes from which it comes, with their treatment in the mill, and with the skill used in firing; but it may be stated broadly that 1 lb of fresh bagasse will produce from 1½ lb to 2¼ lb of steam, according to the conditions.
The use of preparing rolls with corrugations, to crush and equalize the feed of canes to the mill, or to the first of a series of mills, has Extraction of Juice become general. The Krajewski crusher has two such steel rolls, with V-shaped corrugations extending longitudinally across them. These rolls run at a speed about 30% greater than the speed of the first mill, to which they deliver the canes well crushed and flattened, forming a close mat of pieces of cane 5 to 6 in. long, so that the subsequent grinding can be carried on without the stoppages occasioned by the mill choking with a heavy and irregular feed. The crusher is preferably driven by an independent engine, but with suitable gearing it can be driven by the mill engine. The Krajewski crusher was invented some years ago by a Polish engineer resident in Cuba, who took out a patent for it and gave it his name. The patent has expired. The increase in the output for a given time obtained by the use of the Krajewski crusher has been estimated at 20 to 25% and varies with the quality of the canes; while the yield of juice or extraction is increased by 1 or 2%.
The process of continuous defecation which was introduced into Cuba from Santo Domingo about 1900 had by 1910 borne the Purificationtest of some ten years’ use with notable success. The Hatton defector, which is employed for working it, has been already described, but it may be mentioned that the regulation of the admission of steam is now simplified and secured by a patent thermostat—a self-acting apparatus in which the unequal expansion of different metals by heat actuates, through compressed air, a diaphragm which controls the steam stop valve—and by this means a constant temperature of 210° F. (93.3° C.) is maintained in the juice within the defector during the whole time it is at work.Earthy matter and other matter precipitated and fallen on the copper double bottom may be dislodged by a slowly revolving scraper—say every twelve hours—and ejected through the bottom discharge cock; and thus the heating surface of the copper bottom will be kept in full efficiency. With ordinary care on the part of the men in charge Hatton defectors will work continuously for several days and nights, and the number required to deal with a given volume of juice is half the number of ordinary defectors of equal capacity which would do the same work; for it must be borne in mind that an ordinary double-bottomed defector takes two hours to deliver its charge and be in readiness to receive a fresh charge, i.e. 20 minutes for filling and washing out after emptying; 60 minutes for heating up and subsiding; and 40 minutes for drawing off the defecated juice, without agitating it. Apart from increased yield in sugar of good quality, we may sum up the advantages procurable from the use of Hatton defectors as follows: cold liming; heating gently to the temperature required to coagulate the albumen and not beyond it, whereby disturbance would ensue; the continuous separation of the scums; the gradual drying of the scums so as to make them ready for the fields, without carrying away juice or requiring treatment in filter presses; and the continuous supply of hot defecated juice to the evaporators, without the use of subsiding tanks or eliminators; and, finally, the saving in expenditure on plant, such as filter presses, &c., and wages.
Beetroot Sugar Manufacture.—The sugar beet is a cultivated variety of Beta maritima (nat. ord. Chenopodiaceae), other varieties of which, under the name of mangold or mangel-wurzel, are grown as feeding roots for cattle.
About 1760 the Berlin apothecary Marggraff obtained in his laboratory, by means of alcohol, 6.2% of sugar from a white variety of beet and 4.5% from a red variety. At the present day, thanks to the careful study of many years, the improvements of cultivation, the careful selection of seed and suitable manuring, especially with nitrate of soda, the average beet worked up contains 7% of fibre and 93% of juice, and yields in Germany 12–70%, and in France 11.6% of its weight in sugar. In Great Britain in 1910 the cultivation of beet for sugar was being seriously undertaken in Essex, as the result of careful consideration during several years. The pioneer experiments on Lord Denbigh’s estates at Newnham Paddox, in Warwickshire, in 1900, had produced excellent results, both in respect of the weight of the beets per acre and of the saccharine value and purity of the juice. The average weight per acre was over 25½ tons, and the mean percentage of pure sugar in the juice exceeded 15½. The roots were grown under exactly the same cultivation and conditions as a crop of mangel-wurzel—that is to say, they had the ordinary cultivation and manuring of the usual root crops. The weight per acre, the saccharine contents of the juice, and the quotient of purity compared favourably with the best results obtained in Germany or France, and with those achieved by the Suffolk farmers, who between 1868 and 1872 supplied Mr Duncan’s beetroot sugar factory at Lavenham; for the weight of their roots rarely reached 15 tons per acre, and the percentage of sugar in the juice appears to have varied between 10 and 12. On the best-equipped and most skilfully managed cane sugar estates, where the climate is favourable for maturing the cane, a similar return is obtained. Therefore, roughly speaking, one ton of beetroot may be considered to-day as of the same value as one ton of canes; the value of the refuse chips in one case, as food for cattle, being put against the value of the refuse bagasse, as fuel, in the other. Before beetroot had been brought to its present state of perfection, and while the factories for its manipulation were worked with hydraulic presses for squeezing the juice out of the pulp produced in the raperies, the cane sugar planter in the West Indies could easily hold his own, notwithstanding the artifcial competition created and maintained by sugar bounties. But the degree of perfection attained in the cultivation of the roots and their subsequent manipulation entirely altered this situation and brought about the crisis in the sugar trade referred to in connexion with the bounties (see History below) and dealt with in the Brussels convention of 1902.
In beetroot sugar manufacture the operations are washing, slicing, diffusing, saturating, sulphuring, evaporation, concentration and curing.
Slicing.—The roots are brought from the fields by carts, canals and railways. They are weighed and then dumped into a washing machine, consisting of a large horizontal cage, submerged in water, in which revolves a horizontal shaft carrying arms. The arms are set in a spiral form, so that in revolving they not only stir the roots, causing them to rub against each other, but also force them forward from the receiving end of the cage to the other end. Here they are discharged (washed and freed from any adherent soil) into an elevator, which carries them up to the top of the building and delivers them into a hopper feeding the slicer. Slicers used to be constructed with iron disks about 33 to 40 in. diameter, which were fitted with knives and made 140 to 150 revolutions per minute, under the hopper which received the roots. This hopper was divided into two parts by vertical division plates, against the bottom edge of which the knives in the disk forced the roots and sliced and pulped them. Such machines were good enough when the juice was expelled from the small and, so to speak, chopped slices and pulp by means of hydraulic presses. But hydraulic presses have now been abandoned, for the juice is universally obtained by diffusion, and the small slicers have gone out of use, because the large amount of pulp they produced in proportion to slices is not suitable for the diffusion process, in which evenly cut slices are required, which resent a much greater surface with far less resistance to the diffusion water. Instead of the small slicers, machines made on the same principle, but with disks 7 ft. and upwards in diameter, are used. Knives are arranged around their circumference in such a way that the hopper feeding them presents an annular opening to the disk, say 7 ft. outside diameter and 5 ft. inside, with the necessarily division plates for the knives to cut against, and instead of making 140 to 150 revolutions the disks revolve only 60 to 70 times per minute. Such a slicer is capable of efficiently slicing 300,000 kilos of roots in twenty-four hours, the knives being changed four times in that period, or oftener if required, for it is necessary to change them the moment the slices show by their rough appearance that the knives are losing their cutting edges.
Diffusion.—The diffusion cells are closed, vertical, cylindrical vessels, holding generally 60 hectolitres, or 1320 gallons, and are arranged in batteries of 12 to 14. Sometimes the cells are erected in a circle, so that the spout below the slicing machine revolving above them with a corresponding radius can discharge the slices into the centre of any of the cells. In other factories the cells are arranged in lines and are charged from the slicer by suitable telescopic pipes or other convenient means. A circular disposition of the cells facilitates charging by the use of a pipe rotating above them, but it renders the disposal of the hot spent slices somewhat difficult and inconvenient. The erection of the cells in straight lines may cause some little complication in charging, but it allows the hot spent slices to be discharged upon a travelling band which takes them to an elevator, an arrangement simpler than any which is practicable when the cells are disposed in a circle. Recently, however, a well-known sugar maker in Germany has altered his battery in such manner that instead of having to open a large door below the cells in order to discharge them promptly, he opens a comparatively small valve and, applying compressed air at the top of the cell, blows the whole contents of spent slices up a pipe to the drying apparatus, thus saving not only a great deal of time but also a great deal of labour of a kind which is both arduous and painful, especially during cold weather. The slices so blown up, or elevated, are passed through a mill which expels the surplus water, and are then pressed into cakes and dried until they hold about 12% of water and 88% of beet fibre. These cakes, sold as food for cattle, fetch as much as £4 per ton in Rumania, where four or five beetroot factories are now at work. A cell when filled with fresh slices becomes the head of the battery, and where skilled scientific control can be relied upon to regulate the process, the best and most economical way of heating the slices, previous to admitting the hot liquor from the next cell, is by direct steam but as the slightest inattention or carelessness in the admission of direct steam might have the effect of inverting sugar and thereby causing the loss of some portion of saccharine in the slices, water heaters are generally used, through which water is passed and heated up previous to admission to the freshly-filled cell. When once a cell is filled up and the slices are warmed through, the liquor from the adjoining cell, which hitherto has been running out of it to, the saturators, is turned into the new cell, and beginning to displace the juice from the fresh slices, runs thence to the saturators. When the new cell comes into operation and becomes the head of the battery, the first or tail cell is thrown out, and number two becomes the tail cell, and so the rounds are repeated; one cell is always being emptied and one filled or charged with slices and heated up, the latter becoming the head of the battery as soon as it is ready.
Saturation.—The juice, previously treated with lime in the diffusion battery, flows thence into a saturator. This is a closed vessel, into which carbonic acid gas (produced as described hereafter) is forced, and combining with the lime in the juice forms carbonate of lime. The whole is then passed through filter presses, the clear juice being run off for further treatment, while the carbonate of lime is obtained in cakes which are taken to the fields as manure. The principal improvement made of recent years in this portion of the process has been the construction of pipes through which the carbonic acid gas is injected into the juice in such a manner that they can be easily withdrawn and a clean set substituted. The filter presses remain substantially unchanged, although many ingenious but slight alterations have been made in their details. The juice, which has now become comparatively clear, is again treated with lime, and again passed through a saturator and filter presses, and comes out still clearer than before. It is then treated with sulphurous acid gas, for the purpose of decolorization, again limed to neutralize the acid, and then passed through a third saturator wherein all traces of lime and sulphur are removed.
A process for purifying and decolorizing the juice expressed from beetroots by the addition of a small quantity of manganate of lime (20 to 50 grammes per hectolitres of juice), under the influence of an electric current, was worked with considerable success in a sugar factory in the department of Seine-et-Marne in the year 1900–19O1. A saving of 40% is stated to be effected in lime. The use of sulphurous acid gas is entirely abandoned, and instead of three carbonatations with corresponding labour and plant only one is required. The coefficient of purity is increased and the viscosity of the juice diminished. The total saving effected is stated to be equivalent to 3 francs per ton of beetroot worked up. This system is also being tried on a small scale with sugar-cane juice in the West Indies. If by this process a more perfect defecation and purification of the juice is obtained, it will no doubt be highly beneficial to the cane planter, though no great economy in lime can be effected, because but very little is used in a cane factory in comparison with the amount used in a beet factory.
Evaporation and Crystallization.—The clear juice thus obtained is evaporated in a multiple-effect evaporator and crystallized in a vacuum pan, and the sugar is purged in centrifugals. From the centrifugal the sugar is either turned out without washing as raw sugar, only fit for the refinery, or else it is well washed with a spray of water and air until white and dry, and it is then offered in the market as refined sugar, although it has never passed through animal charcoal (bone-black). The processes of evaporation and concentration are carried on as they are in a cane sugar factory, but with this advantage, that the beet solutions are freer from gum and glucose than those obtained from sugar-canes, and are therefore easier to cook.
Curing.—There are various systems of purging refined, or so-called refined, sugar in centrifugals, all designed with a view of obtaining the sugar in lumps or tablets, so as to appear as if it had been turned out from moulds and not from centrifugals, and great ingenuity and large sums of money have been spent in perfecting these different systems, with more or less happy results. But the great achievement of recent manufacture is the production, without the use of animal charcoal, of a cheaper, but good and wholesome article, in appearance equal to refined sugar for all intents and purposes, except for making preserves of fruits in the old-fashioned way. The wholesale jam manufacturers of the present day use this sugar; they boil the jam in vacuo and secure a product that will last a long time without deteriorating, but it lacks the delicacy and distinctive flavour of fruit preserved by a careful housekeeper, who boils it in an open pan with cane sugar to a less density, though exposed for a short time to a greater heat.Carbonatation—The carbonic acid gas injected into the highly limed juice in the saturators is made by the calcination of limestone in a kiln provided with three cleaning doors, so arranged as to allow the lime to be removed simultaneously from them every six hours. The gas generated in the kiln is taken off at the top by a pipe to a gas-washer. In this it passes through four sheets of water, by which it is not only freed from any dust and dirt that may have come over with it from the kiln, but is also cooled to a temperature which permits an air-pump to withdraw the gas from the kiln, through the gas-washer, and force it into the saturators, without overheating. In some factories for refining sugar made from beet or canes this system of carbonatation is used, and enables the refiner to work with syrups distinctly alkaline and to economize a notable amount of animal charcoal.
Refining.—Briefly, sugar-refining consists of melting raw or unrefined sugar with water into a syrup of 27° to 28° Beaumé, or 1230 specific gravity, passing it through filtering cloth to remove the sand and other matters in mechanical suspension, and then through animal charcoal to remove all traces of colouring matter and lime, thus producing a perfectly clear white syrup, which, cooked in the vacuum pan and crystallized, becomes the refined sugar of commerce.
Melting Pans.—The melting pans are generally circular vessels fitted with a perforated false bottom, on which the sugar to be melted is dumped. The pans are provided with steam worms to keep the mass hot as required, and with mechanical stirrers to keep it in movement and thoroughly mixed with the water and sweet water which are added to the sugar to obtain a solution of the specific gravity desired. Any sand or heavy matter in suspension is allowed to fall to the bottom of the pan into the “sandbox” before the melted sugar is run off to the cloth filters. In a process employed with great success in some refineries the raw sugars are washed before being melted, and thus a purer article is obtained for subsequent treatment. In this process the raw sugar is mixed with a small amount of syrup so as to form a suitable magma, and is then run into a continuous centrifugal, where it is sufficiently washed, and from which it runs out, comparatively clean, into the melting pans described above.
Filters.—Taylor bag filters are generally used for clearing the melted liquor of its mechanical impurities. They were introduced years ago by the man whose name they still retain, but they are very different in construction to-day from what they were when first employed. They consist of tanks or cisterns fitted with “heads” from which a number of bags of specially woven cloth are suspended in a suitable manner, and into which the melted sugar or liquor to be filtered flows from the melting pans. The bags, though 60 in. or more in circumference, are folded up in such a way that a sheath about 15 in. in circumference can be passed over them. Thus a maximum of filtering surface with a minimum of liquor in each bag is obtained, and a far greater number of bags are got into a given area that would otherwise be possible, while the danger of bursting the bags by leaving them unsupported is avoided. As the liquor goes on filtering through the bags they gradually get filled up with slime and sludge, and the clear liquor ceases to run. Steam is then turned on to the outside of the bags and sheaths, and hot water is run through them to wash out all the sweets they contain. Large doors at the side of the cistern are then opened, and as soon as the bags are cool enough they are removed at the expense of very exacting labour and considerable time, and fresh bags and sheaths are fixed in their places ready for filtering fresh liquor. The dirty bags and sheaths are then washed, mangled and dried, and made ready for use again. In a refinery in Nova Scotia a system has been introduced by which a travelling crane above the bag filters lifts up any head bodily with all its bags attached, and runs it to the mud and washing tanks at the end of the battery, while another similar crane drops another head, fitted with fresh bags, into the place of the one just removed. The whole operation of thus changing a filter occupies about ten minutes, and there is no need for anyone to enter the hot cistern to detach the bags, which are removed in the open air above the mud tank. By this arrangement the work of a refinery can be carried on with about one-half the cisterns otherwise required, because, although it does not reduce the number of bags required per day for a given amount of work, it enables the refiner to use one cistern twice a day with fresh bags, instead of only once as heretofore. In some refineries the travelling cranes are now run by electricity, which still further facilitates the work. Another method of enabling more work to be done in a given time in a given cistern is the use of a bag twice the ordinary length, open at both ends. This, being folded and placed in its sheath, is attached by both ends to the head, so that the melted liquor runs into both openings at the same time. The mud collects at the bottom of the ⋃, and allows the upper part of the bag to filter for a longer time than would be the case if the bottom end were closed and if the bag hung straight like the letter I,
The clear, bright syrup coming from the bag filters passes to the charcoal cisterns or filters. These are large cylindrical vessels from 20 to 50 ft. high, and of such diameter as to hold a given quantity of animal charcoal (also called “bone-black” and “char”) in proportion to the contemplated output of the refinery. A very usual size of cistern forming a convenient unit is one that will hold 20 tons of char. Each cistern is fitted with a perforated false bottom, on which a blanket or specially woven cloth is placed, to receive the char which is poured in from the top, and packed as evenly as possible until the cistern is filled. The char is then “settled” by water being slowly run on to it, in order to prevent the syrup making channels for itself and not permeating the whole mass evenly. The cistern being thus packed and settled is closed, and the syrup from the bag filters, heated up to nearly boiling point, is admitted at the top until the cistern is quite full. A small pipe entering below the false bottom allows the air in the cistern to escape as it is displaced by the water or syrup. In some refineries this pipe, which is carried up to a higher level than the top of the cistern, is fitted with a whistle which sounds as long as the air escapes. When the sound ceases the cistern is known to be full, and the entrance of further water or syrup is stopped. The syrup in the cistern is allowed to remain for about twelve hours, by which time the char will have absorbed all the colouring matter in it, as well as the lime. A cistern well packed with 20 tons of char will hold, in addition, about 10 tons of syrup, and after settling, this can be pressed out by allowing second quality syrup, also heated to nearly boiling point, to enter the cistern slowly from the top, or it may be pressed out by boiling water. By carefully watching the flow from the discharge cock of the cistern the change from the first liquor to the next is easily detected, and the discharge is diverted from the canal for the first liquor to the canal for the second liquor, and, when required, to the canals for the third and fourth liquors. Finally, boiling water is admitted and forces out all the last liquor, and then continues to run and wash out the sweets until only a trace remains. This weak solution, called “sweet water,” is sometimes used for melting the raw sugar, or it is evaporated in a multiple-effect apparatus to 27° Beaumé density, passed through the char filter, and cooked in the vacuum pan like the other liquors. After the sweets have come away, cold water is passed through the char until no trace of lime or sulphate of lime is found in it; then a large manhole at the bottom of the cistern is opened, and the washed and spent char is removed. In most modern refineries the cisterns are so arranged that the spent char falls on to a travelling band and is conducted to an elevator which carries it up to the drying floor of the charcoal kiln.
Retorts for Reburning Char.—The kilns are made with either fixed or revolving retorts. The former perhaps produce a little better char, but the latter, working almost automatically, require less labour and attention for an equal amount of work, and on the whole have proved very satisfactory. From the drying floor on which the spent char is heaped up it falls by gravitation into the retorts. These are set in a kiln or oven, and are kept at as even a temperature as possible, corresponding to a dull cherry-red. Below each retort, and attached to it, is a cooler formed of thin sheet-iron, which receives the hot char as it passes from the retort, and at the bottom of the cooler is an arrangement of valves which permits a certain amount of char to drop out and no more. With the fixed retorts these valves are worked from time to time by the attendant, but with revolving retorts they are worked continuously and automatically and allow from sixteen to twenty-four ounces of char to escape per minute from each cooler, and so make room in the retort above for a corresponding quantity to enter from the drying floor. The reburnt and cooled char is collected and sent back to the char cisterns. In the best-appointed refineries, the whole of the work in connexion with the char is performed mechanically, with the exception of packing the filter cisterns with fresh char and emptying the spent and washed char on to the carrying bands. In former days, when refining sugar or “sugar baking” was supposed to be a mystery only understood by a few of the initiated, there was a place in the refinery called the “secret room,” and this name is still used in some refineries, where, however, it applies not to any room, but to a small copper cistern, constructed with five or six or more divisions or small canals, into which all the charcoal cisterns discharge their liquors by pipes led up from them to the top of the cistern. Each pipe is fitted with a cock and swivel, in such a manner that the liquor from the cistern can be turned into the proper division according to its quality.
Vacuum Pans and Receivers—The filtered liquors, being collected in the various service tanks according to their qualities, are drawn up into the vacuum pans and boiled to crystals. These are then discharged into large receivers, which are generally. fitted with stirrers, and from the receivers the cooked mass passes to the centrifugal machines. As in the beetroot factories, these machines work on different systems, but nearly all are arranged to turn out sugar in lumps or tablets presenting an appearance similar to that of loaf sugar made in moulds, as this kind of sugar meets with the greatest demand. Granulated sugar, so called, is made by passing the crystals, after leaving the centrifugal, through a large and slightly inclined revolving cylinder with a smaller one inside heated by steam. The sugar fed into the upper end of the cylinder gradually works its way down to the lower, showering itself upon the heated central cylinder. A fan blast enters the lower end, and, passing out at the upper end, carries off the vapour produced by the drying of the sugar, and at the same time assists the evaporation. The dry sugar then passes into rotating screen fitted with two meshes, so that three grades of sugar are obtained, the coarsest being that which falls out at the lower end of the revolving screen.
Recent Improvements.—Systematic feeding for the vacuum pan and systematic washing of the massecuite have been recently introduced not only into refineries, but also into sugar houses or factories on plantations of both cane and beetroot, and great advantages have resulted from their employment. The first mentioned process consists of charging and feeding the vacuum pan with the richest syrup, and then as the crystals form and this syrup becomes thereby less rich the pan is fed with syrup of lower richness, but still of a richness equal to that of the mother-liquor to which it is added, and so on until but little mother-liquor is left, and that of the poorest quality. The systematic washing of the massecuite is the reverse of this process. When the massecuite, well plugged and prepared for purging, is in the centrifugals, it is first washed with syrup of low density, to assist the separation of mother-liquor of similar quality, this washing being supplemented by the injection of pure syrup of high density, or “clairce,” when very white sugar is required. The manufacturers who have adopted this system assert that, as compared with other methods, not only do they obtain an increased yield of sugar of better quality, but that they do so at a less cost for running their machines and with a reduced expenditure in sugar and “clairce.” “Clairce” is the French term for syrup of 27° to 30° Beaumé specially prepared from the purest sugar.
Apart from modifications in the details of sugar refining which have come into use in late ears, it should be mentioned that loaf sugar made in, conical moulds, and sugars made otherwise, to resemble loaf sugar, have practically disappeared from the trade, having been replaced by cube sugar, which is found to be more economical as subject to less waste by grocers and housekeepers, and also less troublesome to buy and sell. Its manufacture was introduced into England many years ago by Messrs Henry Tate & Sons, and they subsequently adopted and use now the improved process and apparatus patented in March 1890 by M Gustave Adant, a foreman sugar refiner of Brussels.The following is a brief description of the process and apparatus; as communicated by the courtesy of Messrs Henry Tate & Sons, Ltd.: Groups of cells or moulds are built within and against a cylindrical iron casing, by means of vertical plates inserted in grooves and set radially to the axis of the casing. Each cell is of suitable dimensions to turn out a slab of sugar about 14 in. long—this being about the height of the cell—and about 8 in. wide and about ½ in. to ¾ in. thick. By means of a travelling crane the casing is placed within an iron drum, to which it is secured, and is then brought under an overhead vacuum pan, from which the cells are filled with massecuite. After cooling, the casing is lifted out of the drum by a crane, assisted by compressed air, and is then conveyed by a travelling crane to a vertical centrifugal, inside of which it is made fast. Suitable provision is made for the egress of syrup from the massecuite in the cells when undergoing purging in the centrifugal; and the washing of the crystals can be aided by the injection of refined syrup and completed by that of “clairce.” When this is done, the casing is hoisted out of the centrifugal and the vertical plates and the slabs of sugar are extracted. The slabs are sent by a conveyor to, a drying stove, whence they issue to pass through, a cutting machine, provided with knives so arranged that the cutting takes place both downwards and upwards, and here the slabs are cut into cubes. The cubes fall from the cutting machine on to a riddling machine, which separates those which are defective in size from the rest. These latter pass to automatic weighing machines, which drop them, in quantities of 1 cwt., into wooden boxes of, uniform measurement, made to contain that weight; and the boxes are then conveyed to the storehouse, ready for sale.
History and Statistics.—Strabo xv. i. 20, has an inaccurate notice from Nearchus of the Indian honey-bearing reed, and various classical writers of the first century of our era notice the sweet sap of the Indian reed or even the granulated salt-like product which was imported from India, or from Arabia and Opone (these being entrepôts of Indian trade), under the name of saccharum or σάκχαρι (from Skr. sarkara, gravel, sugar), and used in medicine. The art of boiling sugar was known in Gangetic India, from which it was carried to China in the first half of the 7th century; but sugar refining cannot have then been known, for the Chinese learned the use of ashes for this purpose only in the Mongol period, from Egyptian visitors. The cultivation of the cane in the West spread from Khüzistan in Persia. At Gundé-Shapfür in this region “sugar was prepared with art” about the time of the Arab conquest, and manufacture on a large scale was carried on at Shuster, Süs and Askar-Mokram throughout the middle ages. It has been plausibly conjectured that the art of sugar refining, which the farther East learned from the Arabs, was developed by the famous physicians of this region, in whose pharmacopoeia sugar had an important place. Under the Arabs the growth and manufacture of the cane spread far and wide, from India to Süs in Morocco (Edrïsi, ed. Dozy, p. 62), and were also introduced into Sicily and Andalusia.
In the age of discovery the Portuguese and Spaniards became the great disseminators of the cultivation of sugar; the cane was planted in Madeira in 1420; it was carried to San Domingo in 1494; and it spread over the occupied portions of the West Indies and South America early in the 16th century. Within the first twenty years of the 16th century the sugar trade of San Domingo expanded with great rapidity, and it was from the dues levied on the imports brought thence to Spain that Charles V. obtained funds for his palace-building at Madrid and Toledo. In the middle ages Venice was the great European centre of the sugar trade, and towards the end of the 15th century a Venetian citizen received a reward of 100,000 crowns for the invention of the art of making loaf sugar. One of the earliest references to sugar in Great Britain is that of 100,000 lb of sugar being shipped to London in 1319 by Tomasso Loredano, merchant of Venice, to be exchanged for wool. In the same year there appears in the accounts of the chamberlain of Scotland a payment at the rate of 1s. 9½d. per lb for sugar. Throughout Europe it continued to be a costly luxury and article of medicine only, till the increasing use of tea and coffee in the 18th century brought it into the list of principal food staples. The increase in the consumption is exemplified by the fact that, while in 1700 the amount used in Great Britain was 10,000 tons, in 1800 it had risen to 150,000 tons, and in 1885 the total quantity used was almost 1,100,000 tons.
In 1747 Andreas Sigismund Marggraf, director of the physical classes in the Academy of Sciences, Berlin, discovered the existence of common sugar in beetroot and in numerous other fleshy roots which grow in temperate regions. But no practical use was made of the discovery during his lifetime. The first to establish a beet-sugar factory was his pupil and successor, Franz Carl Achard, at Cunern (near Breslau) in Silesia in 1801. The processes used were at first very imperfect, but the extraordinary increase in the price of sugar on the Continent caused by the Napoleonic policy gave an impetus to the industry, and beetroot factories were established at many centres both in Germany and in France. In Germany the enterprise came to an end almost entirely with the downfall of Napoleon I.; but in France, where at first more scientific and economical methods of working were introduced, the manufacturers were able to keep the industry alive. It was not, however, till after 1830 that it secured a firm footing; but from 1840 onwards it advanced with giant strides.
Under the bounty system, by which the protectionist countries of Europe stimulated the beet sugar industry by bounties on exports, the production of sugar in bounty-paying countries was encouraged and pushed far beyond the limits it could have reached without state aid. At the same time the consumption of sugar was greatly restricted owing to the heavy excise duties imposed mainly to provide for the payment of the bounties. The very large quantity of output made available for export under these exceptional conditions brought about the flooding of the British and other markets with sugars at depressed prices, not unfrequently below the prime cost of production, to the harassment of important industries carried on by British refiners and sugar-growing colonies. In these circumstances, the British government sent out invitations on the 2nd of July 1887 for an international conference to meet in London. The conference met, and on the 30th of August 1888 a convention was signed by all the powers represented except France—namely, by Austria, Belgium, Germany, Great Britain, Italy, the Netherlands, Russia and Spain. France withdrew because the United States was not a party to it. The first article declared that “The high contracting parties engage to take such measures as shall constitute an absolute and complete guarantee that no open or disguised bounty shall be granted on the manufacture or exportation of sugar.” The seventh article provided that bountied sugars (sucres primés) must be excluded from import into the territories of the signatory powers, by absolute prohibition of entry or by levying thereon a special duty in excess of the amount of the bounties, from which duty sugars coming from the contracting countries, and not bounty-fed, must be free. The convention was to be ratified on the rst of August 1890, and was to be put in force on the 1st of September 1891.
The convention of 1888 was never ratified, and it is doubtful whether its ratification was urged, for a bill introduced by the British government in 1889 to give it effect was not pressed, and it was manifest that there was hesitation—which presently became refusal—to uphold the policy of the penalties on the importation of bountied sugar imposed by the seventh article, without which the convention would be so much waste paper.
Eight years later, on the 1st of August 1896, the bounties offered by the governments of Germany and Austria-Hungary were approximately doubled, and France had a bill in preparation to increase hers correspondingly, although it was computed that they were even then equivalent to a grant of £3, 5s. per ton. So wrote Mr Chamberlain, the colonial secretary, on the 9th of November following, to the treasury. The minute plainly stated that it had become a question whether the continued enjoyment of advantages resulting from the importation of cheap bounty-fed sugar to some British industries did not involve the ruin of the British sugar-producing colonies; and that he was not prepared, as secretary of state for the colonies, to accept the responsibility of allowing matters to take their course and to acquiesce in the policy of non-intervention hitherto pursued in regard to the bounties without having satisfied himself as to what such a policy might entail as regarded both the colonies and the exchequer. Mr Chamberlain concluded by asking whether the treasury would consent to sending a royal commission to the West Indies to inquire into the effect of the foreign sugar bounties on their principal industry.
The treasury accepted the proposal, and a royal commission proceeded to the West Indies in December 1896, and reported a few months later in 1897. Only one commissioner, however, denounced the bounties as the real cause of the utter breakdown of trade and of the grievous distress which all three had witnessed and fully acknowledged. But the minute and commission were not barren of result. A fresh conference of the powers assembled at Brussels, on the invitation of the Belgian government, on the 7th of June 1898; and although the British delegates were not empowered to consent to a penal clause imposing countervailing duties on bountied sugar, the Belgian premier, who presided, was able to assure them that if Great Britain would agree to such a clause, he could guarantee the accession of the governments of Germany, Austria, Holland and his own. Of all the countries represented—Germany, Austria-Hungary, Belgium, Spain, France, Great Britain, the Netherlands, Russia and Sweden—only one, namely France, was opposed to the complete suppression of all export bounties, direct or indirect; and Russia declined to discuss the question of her internal legislation, contending that her system did not amount to a bounty on exportation.
Apart from the proceedings at the sittings, much of the actual work of the conference was done by informal discussion, undertaken to discover some means of arriving at a common understanding. Was a compromise possible which would bring about a satisfactory settlement? The British delegates wrote that it appeared that there were at that time but two methods of securing the suppression of the bounty system—an arrangement for limitation of the French and Russian bounties acceptable to the other sugar-producing states, in return for the total abolition of their bounties; or, a convention between a certain number of these states, providing for the total suppression of their bounties, and for the prohibition of entry into their territory of bounty-fed sugars, or countervailing duties prohibiting importation.
The Belgian government thought a compromise might be possible. A proposal was annexed to the procés-verbal of the final sitting, and the president closed the first session of the conference on the 25th of June 1898 with the expression of a hope that the delegates would soon reassemble.
The annual aggregate output of cane and date sugar in India was short of 4,000,000 tons. Exportation had long ceased, partly owing to the bountied competition of beet sugar, and partly because the people had become able to afford the consumption of a greater quantity than they produced; and German and Austrian sugars were pouring into the country to supply the deficiency. But the importation of foreign sugar, cheapened by foreign state aid to a price which materially reduced the fair and reasonable profit of native cultivators, was a state of things the Indian government could not accept. On the 20th of March 1899 an act, authorizing the imposition of countervailing duties on bounty-fed articles at the port of importation, was passed by the Council of India, and received the assent of the governor-general.
This decisive step was not long in making itself felt in the chanceries of Europe. In October 1900 a conditional agreement for the reduction of the bounties was made in Paris between France, Germany and Austria-Hungary; in February 1901 the Belgian government proposed a new session of the Conference of 1898, and on the 16th of December following Brussels welcomed once more the delegates of all the powers, with the exception of Russia, to the eighth European Sugar Bounty Conference since that of Paris in 1862. The discussion lasted over eight sittings but the conference, to which the British delegates had come with powers to assent to a penal clause, arrived at an understanding, and a convention was signed in March 1902. This was ratified on the 1st of February 1903, subject to a declaration by Great Britain that she did not consent to penalize bounty-fed sugar from the British colonies.
It was agreed “to suppress the direct and indirect bounties which might benefit the production or export of sugar, and not to establish bounties of this kind during the whole duration of the convention,” which was to come into force on the 1st of September 1903, and to remain in force five years, and thenceforward from year to year, in case no state denounced it twelve months before the 1st of September in any year. A permanent commission was established to watch its execution.
The full text in French, with an English translation, of the Sugar Convention, signed at Brussels on the 5th of March 1902 by the plenipotentiaries of the governments of Germany, Austria-Hungary, Belgium, Spain, France, Great Britain, Italy, the Netherlands and Sweden, will be found in a return presented to parliament in April 1902 (Miscellaneous, No. 5, 1902, Cd. 1013).
Table I.—Amounts (reduced to English money per cwt. avoirdupois) of the total net sugar bounties granted by European powers, according to the computation issued by the secretary of the United States treasury on the 12th of December 1898.
|Bounties (per. cwt.)|
|s. d.||s. d.||s. d.||s. d.||s. d.||s. d.||s. d.||s. d.||s. d.||s. d.|
|Russia||2 3.3||2 11.1||3 4.65|
|Austria-||1 2||1 3||1 9.3|
|Germany||1 3||1 6||1 9.3|
|Sugars classed as (per cwt.)|
|Raw Sugar.||Refined Sugar.|
|Sugars analysing in pure sugar (per cwt.)|
|Hard Dry Refined.|
|Less than||98%||98% and over||(Additional)|
|Country—||s. d.||s. d.||s. d.|
|Holland||1 10 8||1 6||0 3|
Sir H. Bergne reported on the 27th of July 1907 to Sir Edward Grey that-
On the 1st of August 1907 the Belgian minister in London transmitted to Sir Edward Grey a draft additional act prepared by the commission for carrying out the proposal of His Britannic Majesty’s government, and on the 28th of August following an additional act was signed at Brussels by the plenipotentiaries of the contracting parties, by which they undertook to maintain the convention of the 5th of March 1902 in force for a fresh period of five years.
On the 2nd of December 1907 Sir H. Bergne wrote to the foreign office from Brussels, reporting that a special session of the permanent commission, established under the sugar bounties convention, had opened on the 18th of November, and the principal matter for its consideration had been the application of Russia to become a party to the convention on special terms. A protocol admitting Russia to the sugar convention was signed at Brussels on the 19th of December 1907.
Sir A. H. Hardinge on behalf of Great Britain made the following declaration:-
When, in April 1908, Mr Asquith became premier, and Mr Lloyd George chancellor of the exchequer, the sugar convention
The quantities of cane sugar are based on the trade circulars of Messrs Willett & Gray of New York: those of beet sugar on the trade circulars of Messrs F. O. Licht of Magdeburg; and the prices are obtained from statements supplied by importers into the United States of the cost in foreign countries of the sugars which they import. The table has been adapted from the Monthly Summary of Commerce and Finance of the United States, January 1902, prepared in the Bureau of Statistics, Treasury Department, Washington Government Printing Office, 1902.
|Year.||Raw Cane.||Raw Beet.||Refined Cane.||Refined Beet.||Total.||Consumption per head.||Total.||Price per cwt.|
of 1902 had thus been renewed in a modified form. Great Britain, instead of agreeing to prohibit the importation of bounty-fed sugar, was allowed to permit it under certain limits. Russia, which gave bounties, was to be allowed to send into European markets not more than 1,000,000 tons within the next five years, and Great Britain undertook to give certificates guaranteeing that sugar refined in the United Kingdom and exported had not been bounty-fed. The renewal of the convention was disapproved by certain Liberal politicians, who insisted that the price of sugar had been raised by the convention; and Sir Edward Grey said that the government had intended to denounce the convention, but other countries had urged that Great Britain had induced them to enter into it, and to alter their fiscal system for that purpose, and it would be unfair to upset the arrangement. Besides, denunciation would not have meant a return to prior conditions; for other-countries would have continued the convention, and probably with success, and would have proposed prohibitive or retaliatory duties in respect of British sugar, with bad results politically. Still the British government had been prepared to denounce the convention in view of the penal clause which had ensured the exclusion of bounty-fed sugar, either directly or through the imposition of an extra duty. But this had been removed, and it was now unreasonable to insist on denunciation. Russia would have made the same arrangement she had obtained had we seceded from the convention. She had formerly sent to England about 40,000 tons of sugar yearly; she might now send 200,000 tons. Was this limitation a reason for sacrificing the advantages we had gained? Under the original terms of the convention Great Britain might have been asked to close her ports to sugar proceeding from one country or another. This was now impossible.
The cane and beet sugar crops of the world for 1909–1910, with the average of the crops for the seven preceding years from 1902–1903, in tons of 2240 lb.
A.-Cane sugar (compiled from the Weekly Statistical Sugar Trade Journal of Messrs Willett & Gray of New York, and books and reports published under the authority of the government of India).
for 7 years end-
|Africa—||Tons avoidupois||Tons avoidupois|
|Total in Africa||365,000||312,436|
|Antigua and St. Kitts||25,000||21,857|
|Total in British Colonies||243,000||243,471|
|Danish Colony, St Croix||15,000||12,857|
|Danish Colony, Surinam||15,000||13,149|
|Total in French Colonies||80,000||71,779|
|Haiti and Santo Domingo||90,000||56,043|
|Total in United States||1,105,000||890,995|
|Total in America||3,995,000||3,107,252|
for 7 years end-
|Asia—||Tons avoidupois||Tons avoidupois|
|British India and
Java and Madoera
|Japan and Formosa||130,000||94,225|
|United States possession—
|Total in Asia||5,232,000||5,845,432|
|Australia and Polynesia—|
|New South Wales||14,500||20,706|
|Total in Australia and
|Total in Europe||16,000||19,743|
|Australia and Polynesia||219,500||214,634|
|Total production of cane
sugar in the world
B.-Beet sugar (compiled from data furnished by the Statistisches Bureau für die Riibenzucker Industrie des Deutschen Reiches, of Mr F. O. Licht, Magdeburg).
|Average of 7|
|Total crop of the world||5,665,796||5,977,189||4,840,798||7,102,080||7,030,989||6,891,876||6,818,458||6,505,607||6,332,455|
The matter temporarily dropped, but certain Liberal members of parliament continued to press for the withdrawal of Great Britain from the convention, it being stated that a promise had been privately given by Sir Henry Campbell-Bannerman that the government would withdraw as soon as practicable. On the 15th of July 1908, Mr Asquith said that Sir Edward Grey had announced in the House of Commons on the 6th of June 1907 that the British government intended to negotiate with the powers for the renewal of the convention, on condition that they would relinquish the penal clause, and that none of the obligations in the convention as renewed were penal or required statutory authority.
Tables II., III. (p. 773) and IV. (p. 774) give statistics of cane and beet sugar production.
The quantities for India have been computed from information furnished by the India office, and publications made under authority of the secretary of state and the commercial intelligence department of the Indian government.
The whole of the sugar produced in India is consumed In the country and sugar is imported, the bulk of it being cane sugar coming from Mauritius and Java, and about 85% of the import, is of high quality resembling refined sugar.
It would appear that the purchasing power of the inhabitants of India has increased of late years, and there is a growing demand for rehned sugar, fostered by the circumstance that modern processes of manufacture can make a quality of sugar, broadly speaking, equal to sugar refined by animal charcoal, without using charcoal, and so the religious objections to the refined sugars of, old days have been overcome. (A. Ch.; V. W. Ch.)
- See Fermentation; and for the relation of this property to structure see Stereoisomerism.
- These formulae, however, require modification in accordance with the views of Lowry and E. F. Armstrong, which postulate a γ oxidic structure (see Glucose). This, however, does not disturb the tenor of the following arguments.
- To distinguish the isomer ides of opposite optical activity, it is usual to prefix the letters d- and l-, but these are used only to indicate the genetic relationship, and not the character of the optical activity; ordinary fructose, for example, being represented as d-fructose—although it exercises a laevorotatory power—because it is derived from d-glucose.
- The following account is mainly from H. E. Arrnstrong's article Chemistry in the 10th edition of this Encyclopaedia; the representation differs from the projection of Meyer and Jacobsen.
- Lucan iii. 237; Seneca, Epist. 84; Pliny, H.N. xii. 8 (who supposes that sugar was produced in Arabia as well as in India); Peripl. mar. Efyth. § 14; Dioscorides ii. IO4. The view, often repeated, that the saccharum of the ancients is the hydrate of silica, sometimes found in bamboos and known in Arabian medicine as tabdshïr, is refuted by Yule, Anglo-Indian Glossary, p. 654 see also Nat. et extr. des MSS. de la bibl. nat. xxv. 267 seq.
- Marco Polo, ed. Yule, ii. 208, 212. In the middle ages the best sugar came from Egypt (Kazwini i. 262), and in India coarse sugar is still called Chinese and fine sugar Cairene or Egyptian.
- So the Armenian Geography ascribed to Moses of Chorene (q.v. for the date of the work); St Martin, Mém. sur l'A1ménie, ii. 372.
- Istakhri p. 91; Yâküt ii. 497. Tha‘âlibï, a writer of the 11th century, says that Askar-Mokram had no equal for the quality and quantity of its sugar, “notwithstanding the great reduction of ‘Iräk, Jorjän and India.“ It used to pay 50,000 lb of sugar to the sultan in annual tribute (Latdäif, p. 107). The names of sugar in modern European languages are derived through the Arabic from the Persian shakar.