Popular Science Monthly/Volume 23/October 1883/The Sayings of Science
By P. L. SIMMONDS.
IN the last quarter of a century, very important progress has been made in our home industries and foreign commerce; but certainly the success that has been effected in the utilizing of waste products, and developing neglected ones, is not the least remarkable of recent scientific advances.
It is evident that, when considered from the point of view of industrial science, the phrase, "utilization of waste," may be fairly applied not only to the unused residual products of manufactures, but to the boundless, undeveloped wealth of nature. The beautiful aniline dye, produced from the tar of the gas-works, is not more an example of the utilization of waste than beet-root sugar, obtained from what, a century ago, was a weed growing by the sea-side. Nature produces, abundantly and spontaneously, in many countries, vegetable substances (such, for instance, as the esparto-grass), which were long allowed to run to waste. Important industrial uses have been found for many of them, and fortunes realized by numbers who have turned their attention toward rendering them articles of commerce.
The flesh of domestic animals fit for food is almost a waste substance in many countries, since it can not be locally consumed nor profitably preserved. In the River Plate republics alone there are 80,000,000 sheep and 25,000,000 cattle to a population of 2,500,000. For years sheep were only valued there for their wool, and, when flayed, carcasses were left to rot, or, when dried in the sun, piled up in stacks for fuel, while later on they were boiled down for their tallow. Sheep get very fat in the province of Buenos Ayres, and those of three and four years will give frequently from eighteen to twenty-five pounds of tallow. Countless numbers of sheep are boiled down every year in the so-called graseŕias only for the tallow, which forms one of the staple articles of export. The mutton is thrown away, or used in a dry state as fuel.
In the five years ending with 1850, more than 1,500,000 sheep and 200,000 horned cattle were boiled down simply for their tallow, in the colonies of New South Wales and Victoria.
We English are great meat-eaters, and, as our home supply is quite insufficient, we have to import more than 000,000 tons every year. With the growth of our population, and the decreasing number of live-stock at home, the imports of meat from abroad have prodigiously increased in the last quarter of a century.
In a paper read before the Royal Colonial Institute, Sir Francis Bell, the Agent-General for New Zealand, stated that frozen meat in any quantity can be placed upon this market from the other side of the world at 6d. to 62d. a pound, leaving a good profit to the grower. "This," he added, "ought ultimately to make meat cheaper here, or at least prevent the further rise now threatened. Australia and New Zealand can, in fact, export 700,000 tons of meat a year, or 2,000 tons a day, which is not much more than you want in England even now, without reducing even the present capital number of their sheep and cattle, and we are able to send on sheep to Smithfield with greater ease to-day than the Tweed farmers could one hundred years ago, when meat was selling at a penny a pound in Scotland against tenpence in London."
Horses, although numerous in some countries, as in Russia and the River Plate states, have not been, commercially, very useful when dead. In South America mares are never broken to the saddle, and the carcasses are generally boiled down for their fat, the exports of mares' grease being considerable, while the hide is also useful. But, within the period now under our notice, horse-flesh has come largely into use on the Continent for human food. Its sale has become a legalized and recognized trade in many of the Continental states, especially in France and Germany. The published statistics of the Society for Promoting the Use of Horse-flesh show that, since its foundation in July, 1860, 100,080 horses, 6,690 donkeys, and 395 mules had been sold in Paris alone for food, up to the end of 1881, furnishing 67,809,460 pounds of meat. Horse-flesh is sold at half the price of beef. The innovation has gained ground rapidly in most of the principal towns of France, and the public sale of horse-flesh for human food is now general in Austria, Prussia, Bohemia, Saxony, Hanover, Switzerland, Belgium, and Sweden. In England, the hundreds of horses which die in the metropolis are sent, with other carcasses, to special firms, which utilize every part commercially. The skin is removed, and the bones are taken out with great expedition; the flesh is then placed in caldrons, of a capacity of 600 gallons. Upon boiling the flesh, the oil is separated, and used by soap-makers and leather-dressers. The bones are also boiled, yielding further oil and fat, and are afterward utilized for manure.
In the United States there was formerly a plethora of waste. The time was when, in Cincinnati, Chicago, and other slaughtering centers, the food of millions was cast out and allowed to be entirely lost by being thrown into the river, or burned in large pits. Now, such is not the case, for the poor but industrious German and Irish populations have saved much of this extravagant waste, and, by their cheaper labor, almost the whole of these substances has been converted to profitable use. Even now a great deal of the ox is disused, which in Europe is esteemed most nutritious food.
There is an important industry which has sprung up out of animal waste, in the utilization of purified tallow and other fats for food and domestic purposes. It was originated in France in 1869 by M. Mége, and was intended for the manufacture of artificial butter from fat, by extracting the oil at a low temperature, and converting this, by churning, into butter. It was first known as oleomargarine, then as margarine, and latterly as butterine. The manufacture of this product has spread extensively, and it is carried on in the United States on a very large scale. As a London trade journal observed, a few weeks ago, "It is to be regretted that shopkeepers do not see their way to offer it to the public under its proper name, a proceeding which would be not only more honest, but which would ultimately tend to the more general adoption of butterine as an article of daily consumption."
From statistics prepared by Mr. Nimmo, of the United States Department of Agriculture, it appears that more than one third of the American exports of butter are sworn to be oleomargarine. Now, as we receive over 8,700 tons of so-called butter from North America, it is not pleasant to know that one third of this is the artificial butterine. Not only is margarine thus used, but, under the name of sueine, much lard is now introduced into the butter.
In the utilizing of inferior or waste materials, and in the separating of tallow from the substances with which it is found in combination, machines are employed which are both ingenious and effective, and by their use much material that would otherwise be worse than useless is turned to good account.
In Europe, rabbits are not a waste substance, but are eagerly sought for as food, and even bred in large numbers; but their introduction into Australia and New Zealand has proved an unmitigated evil to the colonists. About twenty years ago there was not a single rabbit in Australia, save, perhaps, a few domesticated pets. Since their introduction they have become a perfect pest, and the difficulty is to exterminate and keep them down by poison, dogs, etc.
From New Zealand alone 8,500,000 rabbit-skins were exported in 1880, but this does not probably represent one tenth part of the animals actually destroyed. In that climate the rabbit breeds nearly every month in the year. But even supposing that a pair of rabbits do not breed oftener than in England, which is seven times a year, and that they only bring eight young at a time, they would multiply in the course of four years to 1,250,000. Besides the skins shipped to England and America, the colonists are trying to send us rabbits' flesh in tins. Rabbit-skins are in demand by the furrier. About 30,000,000 indigenous rabbit-skins and 2,000,000 or 3,000,000 hare-skins are used up in this country. The skins of those which are not used or dyed as furs are, after the hair has been pulled for the hat-maker and for stuffing beds, employed for glove-making. The hair is also now used for making yarn and cloth.
The wool manufacture, in almost all countries, now uses up cuttings of cloth and shreds of all kinds which were formerly thrown away. These, and the strippings and waste in carding, are now classed immediately after pure wool, and command relatively high prices. There are many who may be disposed to regard the shoddy manufacture as a business to be despised, but the political economist discovers in it a most important source of wealth—wealth resulting from the application of skilled labor to the utilization of material once worthless, but now contributing no mean sums annually to the wealth of nations.
There are now 137 shoddy-factories, principally situated in the Yorkshire district, which employ over 5,000 persons, 3,000 of whom are females. About 40,000 tons of woolen rags are annually torn into shoddy in England alone, and the quantity made in the United States must be almost equal. No accurate data can be found of the European use of these articles, but an immense quantity of both shoddy and mungo is now made and exported from the Continent, principally to England, and it is probable that the whole of the world's annual consumption is over £7,000,000 in value. At the recent International Wool Exhibition, held at the Crystal Palace under my charge, there were shoddies sent from most of the states of Europe. Italy first began to work woolen rags into yarn in 1858, and most of the other European countries followed the example.
Raw silk having become scarce and dear of late years, much more attention has been given to the employment of the different sorts of silk waste, for which, at one time, scarcely any use could be found.
The variety of these is very large, and most of them are now profitably and extensively employed. The outside and inside husks of the cocoons used to be mere refuse. These pass under various trade names in different countries; in England, as "knubs and husks" and "floss silk"; on the Continent, as bourre de soie, frisonets, and floret. What is termed "yarn waste" is the waste made by the silk throwster. The pierced cocoons, that have been eaten through by the moths, are now largely employed in the preparation of chappe, or schappe. Then there are the noils and thread waste from the silk-factories.
In 1857 the imports of these waste silks were only 18,000 hundredweight, valued at £302,286. In 1881 the imports reached 540,119 hundred-weight, valued at 757,796. France, Switzerland, Germany, Great Britain, and the United States have now entered extensively into the utilization of silk waste for manufactures, which was formerly a drug in the market. In the Swiss report on the Paris Exhibition of 1867, it was stated that the annual production of floss-silk yarns then ranged in value from £400,000 to £600,000. In 1872 about 7,750,000 pounds of thread were made from waste silk in Europe. In the United States, 2,000 to 3,000 bales of waste silk are used up annually, valued at 200,000. Italy exports annually about 5,000,000 pounds of silk waste.
There are fifteen establishments in France, with 479,353 spindles, working up waste-silk; that is, the waste from the cocoon not reelable, the short pieces, etc. What remains over from this working is again used up by seven other factories, which, by means of further combing and carding, employ waste formerly only partially utilized or altogether lost to consumption.
In connection with this subject I may draw attention to the stimulus given to the collection of the cocoons of the wild silk-worm of India, known under the name of Tusser. These, which were formerly only used in the East for making a kind of drab or coffee-colored silk, have now been made to take dyes, and are profitably employed in the silk manufacture in England. The waste of the wild cocoons in China and Japan is made into felt for hats, and enters into the manufacture of paper.
The improvements in machinery for the preparation and spinning of silk-waste have made great strides of late, and whereas a few years ago one never heard of anything but "spun-silk" hosiery, handkerchiefs, or some other little article of similar make, the whole world now knows the schappe velvets of Crefeld, the "spun" ribbons of Basle, and the laces of Nottingham, while the king of silk-spinners—Lister, of Manningham—has even produced machine-twist of excellent quality from this unlikely material.
The refuse from the tanneries, now so profitably utilized, is of considerable importance; it consists of untanned dried pelt, or glue-pieces, fleshings, hair, lime deposit, and spent-tan. Glue-pieces or "scrolls," as they are termed, are sold to the paper-maker, and scores of tons for the manufacture of gelatine and portable soups. Ordinary size is made from the flesh refuse of the hide, and is extensively used by paper-hangers, cotton-spinners (to give firmness to the thread), and carpet manufacturers. The so-called cheap seal-skins are manufactured in the north of England from common plasterers' hair, or that obtained from the tan-pits. There has been made for many years, in Germany, printing-paper and cardboard of the waste bark from tanneries. The common papers receive about ten or fifteen per cent of this pulp; the boards for roofing from twenty to forty per cent. Artificial leather is also now extensively made from leather cuttings, pressed and rolled into sheets with some glutinous composition.
Latterly it has been found that leather-waste cuttings, etc., when steamed with certain waste liquors, produce a valuable material in the shape of a new black, which is destined to have a variety of important uses, such as in the manufacture of printing-inks, dark pigments, covering substances, and notably for the manufacture of blacking. Bone-black, from which the latter is chiefly made, costs £9 per ton, and the supply is limited, while this new tannic black can be sold at one third of the price.
The blood from the slaughter-houses, which used to be wasted, is now collected in Europe, and utilized for manufacturing into blood albumen, which sells at about 1s. a pound. The drainings and the clot go for manure.
Among the miscellaneous animal substances now utilized, we find many species of fish-skin tanned, such as the so-called porpoise-skin, (Beluga catodon). Alligators and crocodiles, and even snakes, are hunted for their skins, which are tanned, and provide a valuable article for making slippers, purses, pocket-books, cigar-cases, etc.
Let us now pass to vegetable substances, and I will first consider the paper manufacture. A recent estimate was published, which set down the paper-mills of the world at 4,000, producing 1,000,000 tons of paper, of which one half was used for printing.
It is now evident that the future of the paper industry will, in a large degree, depend upon the use of wood, which is already extensively employed. For the ordinary varieties of paper, ground wood is used; but, for the finer sorts, chemically prepared wood-fiber, or cellulose, is employed. The practical process for the preparation of cellulose was discovered in 1852, and numerous other processes or improvements have since been invented. It comes into commerce in two forms—wood-pulp in sheets or blocks, and ligneous meal or wood flour. In Central Russia, aspen-wood is most extensively employed; in Sweden and Finland, spruce and fir, which afford the longest fibers; in Germany, France, and Belgium, mixed woods. The pulp from beech and birch woods has too short a fiber.
About twenty years ago, some of the American paper manufacturers used the bamboo largely for making paper. This is no new application, for the Chinese have long employed it for a common description of paper. Good paper is now also made from esparto-grass.
A good deal of the jute sent from India to the United States consists of the dark root, or butt-ends of the fiber, which are cut off when the jute is pressed into bales. These are called "cuttings" in Calcutta, and with us, "rejections"; they now form a regularly quoted article of export to America, where they are employed in the fabrication of various shoddy-stuffs. In former years these cuttings were thrown away. Megass, the refuse stalk of the sugar-cane, makes excellent paper. The husks of oats, barley, rye, and rice, are also used alone, or combined with other materials. Straw-board, of late years, has been found to be a cheaper material than the old-fashioned "pasteboard," and it has come extensively into use in America for paper-boxes. Straw has long been employed as a paper material, but it is often scarce and dear. It is even found profitable to buy up the bedding litter from the metropolitan stables, and, after washing and disinfecting it, to sell it to the paper-mills.
Until a very recent period, the waste-paper of the Government offices of London was the perquisite of the messengers. But when it was found that the aggregate sales of this waste-paper reached the sum of £10,000 to £15,000 a year, it was thought time to look into this, and it was then handed over to the Stationery-office, and, in the last financial year, the sale of waste-paper reached £11,771. The United States Treasury sells yearly more than 600 tons of paper-pulp, resulting from the destruction by maceration of Government securities, bank-notes, etc.
In one large printing and publishing establishment in London, the waste-paper, in shavings and imperfect impressions, exceeds seventy-five tons a year. Even the newspaper-offices now economize and use up their spoiled impressions, or overplus papers, for printing their posters on.
It is only since 1860 that the extraction of the oil from cotton-seed has been carried on on a commercial scale; before that date vast quantities of the seed were allowed to accumulate and to rot on the cotton-plantations. It is an industrial fact of considerable interest and significance, that at the present time the seed is often more valuable to the planters for its oil and oil-cake than the cotton-fiber, for of the latter it contains only about one quarter of its weight.
In the process of refining, the residue of the crude oil is distilled, and, with care, produces a hard grease or stearine, which commands, when of good color, within 3s. or 4s. per hundred-weight the price of Petersburg tallow. The by-product is used for making artificial butter. Even the foots, or tarry residue, is useful as a paint ingredient.
It would be difficult to define the limits to which the indirect consumption of Indian corn extends. Every pound of American pork eaten, the laundry and food starches used, the large production of alcohol (that of whisky in the States is 67,000,000 gallons), the varnishes used by the cabinet-maker, the perfumery of the toilet-table, the different kinds of illuminating fluids, all indicate the universality of the employment of maize.
It was in 1867 that a new use was found for maize, by converting it into glucose. The report of the New York Chamber of Commerce states that the production of this sugar is now not less than 1,000 tons a day for the whole United States.
In America, they are also endeavoring to utilize the immense quantities of pulp remaining from the corn after the extraction of the starch. This pulp, which is at present a waste product, consists wholly of cellulose or woody fiber, and would, it is considered, be an excellent material for making the commoner grades of paper, suitable for wrapping and newspaper purposes.
The present sources of the supply of potash are rapidly failing; every year the area of the supply becomes smaller, and the product, in consequence of this and the increased demand, becomes more and more expensive. The cobs of Indian corn, which are now considered of little or no value, may yet share the same fate as many substances which, though formerly considered worthless, have become new mines of wealth, through the aid of chemistry.
The average yield of 1,000 parts of cobs is 7·62 parts of carbonate of potash, or nearly twice as much as the best specimens of wood, and it is a material which can fill its full measure of usefulness for other purposes, before it comes into the hands of the manufacturer of potash. At the shipping ports, large shelling-mills are established, capable of running through 500 bushels of corn an hour. Here, then, are the places where a supply of cobs may be procured.
The corn-crop of North America varies; but, taking the yield of 1871—1,100,000,000 bushels, at fourteen pounds of cobs to the bushel—this would yield 7,700,000 tons of cobs, containing an average of three quarters per cent of pure carbonate of potash. The enormous quantity of 115,500,000 pounds of that useful article might thus be thrown into commerce. In some districts, these corn-cobs are extensively used as fire-lighters, being dipped into a composition of resin and tar, and then dried.
It is only some twenty years now since glycerine, a by-product in the manufacture of soap and candles, has been produced on a commercial scale, but the quantity now made represents an annual value of nearly a quarter of a million sterling. Glycerine has thus attained to a position of considerable technical importance. The introduction of the stearine-candle industry and the efforts to utilize the heretofore waste products of the soap manufacture demonstrated its existence in considerable quantity. The important uses to which this substance is now applied are so numerous that it would be difficult to enumerate them.
There is a large consumption of cork-bark, in this and other countries (the quantity we import exceeds in value half a million sterling), and even in this direction the economizing of the waste is found profitable and useful. The suberine powder is made into cork carpets for floor-cloth, and it is even used by chemists in place of lycopodium, powdered rice, starch, etc. Old corks are collected, and cleaned with hydrochloric acid and hot water, so as to be used again. The Paris sewers are provided with gratings, and the corks thus collected are recut, and used again. All cork cuttings are useful for filling life-buoys, belts, jackets, and even beds.
In Europe, as much use has not been made of sea-weed as in China and Japan, where it forms a very large article of consumption for food. In China, it is imported both from Japan and Asiatic Russia, to the extent of more than 25,000 tons a year. It is received in two forms: first quality, cut, and some known as agar-agar; and second quality, long. This sea-weed is principally consumed by the lower classes of Chinese as a condiment or flavoring, with their rice or other food.
Another product into which sea-weed is converted is gelose—a sort of vegetable isinglass. Viewed from whatever direction, the more general utilization of sea-weed is a most important matter. In some of the northern countries of Europe, cattle are fed on it. Formerly, iodine was only obtained in any quantity from the kelp of sea-weed, but it now appears likely that it can be produced in Peru at a comparatively small cost, as a by-product extracted during the process of manufacturing nitrate of soda; while the necessary arrangements for the manufacture of iodine from kelp are very costly, and the works and machinery used require a large sum of money. It is possible that 5,000 or 6,000 hundred-weight of iodine might be manufactured in Peru at a low cost, but the war with Chili interfered materially with the production. With the exception of the manufacture of kelp, the principal use of sea-weed is for manuring land. Under the name of carrageen, or Irish moss, some is used for food. In France, a gelatine or gum is prepared from sea-weed, which is variously useful in the arts, as in finishing cotton fabrics, making artificial leather, etc. When chemically prepared and pressed, it was, at one time, used extensively for the manufacture of a substitute for horn, called laminite, but this has been dropped. It has occasionally been made into paper.
There is an application of waste substances of vegetable origin that is largely carried on, which certainly does not merit approval, being, for the most part, prosecuted for the purposes of deception and fraudulent gain, and this is in substitutes for, or additions to, coffee. Figs, date-stones, lupines, malt, chiccory, etc., are largely sold, besides the seeds of a stinking weed (Cassia occidentalis) which, when roasted, according to French authorities, is equal to coffee. While the production of coffee is fully equal to the demand, and the price is moderate, I can not see the necessity for these various substitutes. The more legitimate use of date-stones is that to which they are put by the Arabs. They are soaked in water for two or three days, and, when somewhat softened, used to feed their camels, cows, and sheep. There are shops in Medina where they sell only date-stones, and the poor often occupy themselves in collecting the date-stones thrown about the streets by those who eat dates.
Cocoa is not so largely consumed in this country as on the Continent. But the cocoa shells or husks which are separated from the nibs after sifting are imported here to the extent often of 500 tons annually, paying a duty of 2s. a hundred-weight, against 9s. 4d. a hundredweight charged on cocoa and chocolate. These shells or husks form about twelve per cent of the weight of the beans. In the manufacture of the finer chocolates they are always separated, and hence accumulate in large quantities in France and Spain. In the cheaper kinds of chocolate and cocoa, these husks are ground with the nibs, and some other cheap farinaceous substance is added. The black appearance of such chocolate is unmistakable; it will always be found gritty and rough, and, of course, difficult of digestion. The husks are no better than sawdust, and may cause irritation by the minute spiculæ left after grinding.
I must now touch upon the utilization of mineral waste.
The utilizing of tin-plate cuttings and the recovery of the tin have become important and profitable industries. In the manufacture of tin-ware, it is said six per cent of the whole of the plates employed disappears in the form of scrap. Birmingham produces thirty tons per week. Mr. Beck, of that town, is said to have made a profit for many years of £100 a week by taking off the tin from the scrap by solution and precipitation. A very fair trade is done by parties who go about the tin-works buying up the tin-dust. They even go to France and other countries, and ship it to England to be reduced. This so-called tin-dust is really the scum of the tin-pot, and, as it is mixed with grease, it is black. It contains a considerable quantity of metal, which is reduced by ignition and flux. An engineering paper States that the waste of tinned iron, used for all kinds of purposes, but especially for saucepans, kettles, button-making, etc., was formerly large, but a method is now employed by which the tin can be recovered from the waste, simply by the action of dilute sulphuric acid. Tin, to the extent of from five to fifteen per cent, and worth about §97 per ton, with a vast amount of sulphate of iron, is thus procured, giving a large profit on the operation.
Within the last quarter of a century, that formerly neglected mineral—pyrites—has been turned to useful purposes, to supply our manufacturers with the important material, sulphur.
In wire-making factories, the dilute sulphuric acid, formerly used to clean the wire, was allowed to run into the sewer, when it had become so charged with the iron scale as to cease to "bite," and large quantities of refuse wire were employed only to fill up hollows in grading, or thrown into a heap. All this waste material is now r, however, converted into articles of commercial value. The processes are simple and comparatively inexpensive.
Not only in the inferior metals is waste now prevented, but increased attention is given to the collection of gold formerly lost. Immense heaps of refuse, or "tailings," as they are technically termed, accumulate where mining operations are carried on. The sludge which is emptied from the puddling-mills in Australia contains a considerable quantity of fine gold. Much of this is now recovered, and the yield of gold from it exceeds three pennyweights per ton. The right to wash the tailings is often sold to the Chinese, who are always well satisfied with the result of their labors. The quantity of gold used in the arts, in interior and exterior decorations, in photography, electro-gilding, water-gilding, the ornamentation of china, etc., is very large, and the greater part is practically lost. Jewelers' sweepings from the floors of the workshops are carefully collected, and even the clothes of the workmen are generally saved and sent to the refiner. After a large gold coinage at the Royal Mint, there is always a great deficiency in waste and sweep. The sweep is composed of cinders or dust from the forge, the sweepings of the workshops, broken crucibles, the dross which adheres to the ingots of metal after fusion, and of every waste which can possibly contain minute particles of the metal. This is generally sold. The silver and gold from photographers' waste is also now carefully collected, and forms a considerable item of economy. A method of utilizing the waste of gold-leaf, used in printing and the arts, is by converting it into what is called fleece-gold. The composition is used like the ordinary bronze, except that rather more copal is mixed with it. It is used for all fancy papers for which gold-leaf and bronze have hitherto been used.
The waste of the glass-furnaces—such as pieces of broken glass, flaw-glass, the hearth-droppings, and the glass remaining adherent to the blower's pipe—is utilized again, serving a purpose in the manufacture of glass, similar to rags in paper-making. Agate glass is made by melting waste pieces of colored glass. One to two thousand tons of cullet, or broken glass, are collected in the metropolis alone, and sold to the few city glass-works to be remelted. Broken bottles are now collected and utilized. Thousands of tons of these are broken every year in London alone. Broken "wines" and broken "sodas" are converted to many useful purposes, the latter especially. The broken bottles are utilized for the manufacture of cheap jewelry, chimney-ornaments, and inferior household glass for the manufacturing districts. They are also used for the manufacture of emery powder, glass paper, etc. Some idea of the number of "sodas" broken in the process of filling, corking, cleaning, and distributing may be gathered from the circumstance that one great mineral-water manufacturer in London sold last year one hundred tons. The value of the "metal," as it is styled, is somewhere about ten shillings per ton, but it varies according to the demand. When the market for "fancy goods" is active, broken bottles command a better price. A revival of trade sets this particular industry in motion along with others, and broken bottles are enhanced in value. In fact, broken glass and broken pottery serve many purposes, though it is only lately that economic science has learned how to turn them to account.
The utilization of blast-furnace slag is not new, but has made great progress. Scattered throughout the iron-making districts of Great Britain are many million tons of scoria or refuse from the blast furnaces, which is technically known as "slag." This slag goes on accumulating at the rate of nearly 8,000,000 tons per annum, its bulk being some three times that of the iron from which it has been separated. It forms a heavy incumbrance to iron-masters, demanding the purchase of large tracts of land whereupon to deposit it, while the investment is, of course, wholly unremunerative. There are one or two exceptions to this rule, where the slag is tipped into the sea, and serves to form land for the works, and where some of the iron-works supply slag for the construction of breakwater and training walls. The quantity thus utilized, however, on the Tees is but about 600,000 tons per annum, forming only a small proportion of the whole yield of the district.
In early times, slag was broken up by hand, and used for road making, and it so continues to be used, where it can be had without a heavy cost for transport; but there is only a limited demand for this purpose. On the Continent, where stone is scarce, slag plays a prominent part in road-making, as in Silesia and other similarly situated districts. Another direction in which many attempts have been made to utilize slag, both at home and abroad, is to adapt it for constructive purposes, and various schemes have been devised for transforming the highly refractory slag into bricks, sand, and other materials for building.
It is also applied to the manufacture of artificial stone, and molded into chimney-pieces, window-heads, balustrading, and outside ornamental builders' work generally. The stone is composed of two and a half parts of finely pulverized slag, and two and a half parts of ground brick, to one part of Portland cement. The mixture is run into molds, and sets quickly, the articles being ready for the market in four or five days. Besides bricks and stone articles, the slag is used for making mortar, cement, and concrete. The mortar is a mixture of slag and common lime, the cement being composed of the same materials, with the addition of iron oxides.
Another useful purpose for which it has been successfully utilized is that of glass manufacture. The vitreous character of slag indicates a resemblance to glass in its composition. It does, in fact, contain the principal components of glass, but not in proper proportions, and those in which it is deficient have therefore to be added, with others which are not present. Bottles made of this slag by the Britten Patent Glass Company were shown at the Paris Exhibition in 1878, and received honorable mention.
Another application is to the manufacture of slag-wool. By the action of strong jets of steam, the slag is transformed into a fibrous whitish silicate cotton, which, being metallic, is incombustible, like asbestos. In the construction of new houses with Mansard-roofs, the space between the interior lath, or paneling, and the exterior covering of zinc, slate, or tin, is filled with this slag-wool, which protects from the rigor of frost in winter and the intense heat in summer. If in winter the taps and spouts and water-pipes are covered with this slag-wool, it prevents the freezing of the water and the bursting of the pipes and joints. This slag-wool is also used now by gardeners to cover plants and protect them from the effects of sudden changes of temperature.
In view of the general usefulness of slag, when converted into the various articles described, it is to be hoped, in the interests of commerce and progress, that the practice of its utilization may become more and more extended. Doubtless, human progress will show that what is now the veriest waste will, in the course of time, assume a condition of value. Thus will art be made to approximate to nature, in that it will know no waste.
There are one or two other mineral substances, formerly neglected, which have of late years been applied to very extensive important uses. One of these is asbestos. This was long considered a mere curiosity for making small fire-proof articles. It is the only flexible fibrous mineral substance that is perfectly indestructible by fire or acids, notwithstanding it consists of fibers as fine as the finest linen. Now it is scarcely possible to enumerate all the uses to which it is applied. Among others are, as a roofing material, cement, paint, fireproof coating for inside of factories, theatres, etc., in danger of ignition, felting for steam-pipes, boilers, lining for floors, roofs, etc.
A prominent and peculiar feature in the landscape of the coal mining regions is the enormous heaps of black and apparently useless material collected near the outlet of each mine. As the quantity of small waste coal in the United Kingdom has been estimated at 28,000,000 tons per annum, the utilization of this refuse is a matter of national importance in more senses than one. It is now, in many districts, consolidated into blocks, and, besides what is used at home, 412,310 tons of this patent manufactured fuel were exported last year.
In several foreign countries, the pitch from coal-tar is combined with coal-dust, and pressed into the form of bricks, and an excellent fuel is thus produced, which, it is said, will generate a greater amount of heat than can be obtained from the same quantity of any other combustible material employed for utility or comfort, while, at the same time, it can be stored more compactly and in better shape than either wood or coal. Some 40,000,000 tons of valueless coal-dust, lying in the vicinity of the coal-mines and depots of Pennsylvania, have been thus gradually utilized. In some American factories they have found it cheaper and more advantageous to burn only coal-dust or pea coal. A furnace or grate bar has been specially devised for the purpose of burning this kind of fuel, and there is no doubt, with its increasing uses, but that other convenient devices will be supplied for making it of more practical benefit. The utilization of this waste in the coal-regions of the United States is now a decided success. The American Fuel Company, Pennsylvania, works up large quantities of culm (as the coal-dust is technically called) with pitch into blocks, brick-shaped, weighing but fourteen pounds each. Anything tending to the utilization of what is now waste is of value, when we consider that the amount of anthracite coal sent to market represents but about four fifths of the quantity that is actually raised from the earth, the balance being piled up in unsightly heaps.
Many of the subjects which I have incidentally touched upon have been so elaborately dealt with by specialists in papers before the members of this society, that the ground has been taken from under me, and I am but a gatherer and gleaner, summarizing, as it were, the results of their descriptions. Although, in the period under review, many of the waste products of manufactures, formerly thrown away, have been made to serve a useful purpose, there is yet room for fresh efforts in this direction, and the reward is certain. The manufacturer who discovers a heretofore unknown use for the waste product of his work necessarily cheapens the cost of the principal article of his production, and thus secures an advantage over competitors. Much, as we have seen, has already been done in this way, but there are many other products which could be made under the direction of that mighty converter, chemistry, to yield substances of use and profit.
Science has taught us how to transmute the waste and refuse materials—elements of pollution—into sources of economy and wealth. The utilization of the sewage of great cities for agricultural ends has virtually been a demonstrated success in Paris and many of our own towns. The same success, by patient experiment, is obtainable in many other waste products, which, in ignorance of their value, we suffer to defile our streets, pollute our rivers, and taint the air we breathe. The purification of the outflow of paper-mills and the utilization of the sludge and other waste products are now carried out.
It would have been impossible, in the limits of this paper, to refer in detail to more than a few of the principal examples of the successful use of refuse. But those enumerated will serve to show to how great an extent civilization is daily adding to the useful products of the world, both by economizing its resources and by calling forth new ones with the aid of chemistry.