Popular Science Monthly/Volume 29/August 1886/Recent Progress in Chemistry
|RECENT PROGRESS IN CHEMISTRY|
By H. CARRINGTON BOLTON, Ph. D.,
PROFESSOR OF CHEMISTRY, TRINITY COLLEGE, HARTFORD.
TO many intelligent and cultivated persons not specifically instructed in chemistry, this word recalls confused memories of colored liquids, glistening crystals, dazzling flames, suffocating fumes, intolerable odors, startling explosions, and a chaos of mystifying experiments, the interest in which is proportional to the danger supposed to attend their exhibition. Further reminiscences are of many singular objects in wood, metal, glass, and earthenware, of flasks and funnels, of retorts and condensers, furnaces and crucibles, together with bottles innumerable filled with solids, liquids, and gases, the whole paraphernalia connected by glass tubes of eccentric curves, and displayed in inextricable confusion and meaningless array. Behind this chaos arise vague memories of one discoursing learnedly in a polysyllabic jargon, and attempting to explain the unusual phenomena by the aid of abstruse hypotheses, but utterly failing to remove the sensations of awe and of mystery bordering on the supernatural which overwhelm the hearer—impressions that have clung to chemistry ever since its entanglement with the superstitions of alchemy, astrology, and the "black art."
Persons who undertake to gain through chemical literature a knowledge of what chemists are doing in and for the world encounter a discouraging nomenclature which repels them by its apparent intricacy and its polysyllabic character. Their opinion of the terminology of an exact science is not enhanced when they learn that "black-lead" contains no lead, "copperas" contains no copper, "mosaic gold" no gold, and "German silver" no silver; that "carbolic acid" is not an acid, "oil of vitriol" is not an oil, that olive-oil is a "salt," but "rock-oil" is neither an oil nor a salt; that some sugars are alcohols, and some kinds of wax are ethers; that "cream of tartar" has nothing in common with cream, "milk of lime" with milk, "butter of antimony" with butter, "sugar of lead" with sugar, nor "liver of sulphur" with the animal organ from which it was named.
Readers of chemical writings sometimes fail to appreciate the advantages of styling borax "di-meta-borate of sodium," or of calling common alcohol "methyl-carbinol," and they ignore the euphony in such words as pentamethyldiamidothiodiphenylamindiiodomethylate (a substance begotten and baptized by Dr. Albert Maasen).
Those whose chemical education consisted in attendance on a course of lectures illustrated by experiments performed in their presence, interspersed with occasional recitations from a prosaic text-book which taxed the memory in true Chinese fashion, may be pardoned for retaining very hazy impressions of the true character of the science. On the other hand, many thinking and reading persons recognize the magnitude of the scope and operations of chemistry, and have some appreciation of its benefits to mankind.
The fields of chemistry explored by zealous investigators are prodigious in extent and diversity; in its various sections, analytical, agricultural, pharmaceutical, physiological, and technological, it yields fruit of infinite value to the human race, and, co-operating with other sciences, produces results which promote civilization in the highest degree. So rapidly are new methods of cultivation applied to these fields, so numerous and active are the workmen engaged in tilling them, that the harvest is too abundant for mental storage, and those who survey the operations at a distance are quite unable to apprehend the products. This inability to follow the advances made by chemical science is felt not alone by those whose imperfect and non-technical training has illy fitted them for the task; even the specialist stands aghast at the prospect, and, abandoning attempts to apprehend the progress made in all departments, confines his reading and research to a limited number.
The twelve principal chemical societies of the world have an aggregate membership of nearly nine thousand; almost all of these members are actively contributing to the advancement of chemical science, publishing their results for the most part in periodicals especially devoted to the subject. Excluding transactions of societies and journals
|The membership in these societies is distributed as follows:|
|Deutsche chemische Gesellschaft zu Berlin||2,950|
|Society of Chemical Industry (England)||2,400|
|Chemical Society of London||1,500|
|Société chimique de Paris||560|
|Institute of Chemistry of Great Britain and Ireland||430|
|American Chemical Society||250|
|Society of Public Analysts (England)||180|
|Chemical Society of St. Petersburg||160|
|Associazione chimico-farmaceutica fiorentina||200|
|Chemical Society of Tokio, Japan||86|
|Chemical Society of Washington, D. C.||48|
|Association of Official Agricultural Chemists (U. S. A.)||17|
Much interest is commonly attached to announcements of new forms of matter—an interest out of proportion, perhaps, to the real value of the discoveries. During the last nine years chemists have not failed to sustain this interest, for they have proclaimed no less than thirty-four new elementary bodies. The ambition of these chemists, however, has been greater than their accuracy, for of these thirty-four bantlings but five or six have survived the scrutiny of the doctors, two or three are now in precarious health, and the remainder have been cremated without ceremonies. Of the youthful survivors comparatively little is known; their character is being severely tested, and their future destiny and utility are yet uncertain. The extreme rarity of the minerals in which the new elements have been detected, the excessively small percentages of the new ingredients, the extraordinary difficulties attending their separation from known substances combine to render the investigations laborious, protracted, and costly. From twenty-four hundred kilogrammes of zinc-blende, Lecoq de Boisbaudran, the discoverer of gallium, extracted sixty-two grammes of the precious metal; compared with this element, therefore, gold is both abundant and cheap. Ytterbium, scandium, samarium, thulium, and the rest, will long remain mere chemical curiosities known to but few; probably the most sanguine will not claim for them a future place among substances of economic value.
But of far greater importance than the elements themselves is the marvelous delicacy of the means used in detecting and isolating them. When Bunsen and Kirchhoff presented to scientists the instrument which combines the penetration of a telescope with the power of a microscope magnified a hundred-fold, they were enabled to disclose Nature's most hidden secrets. The new elements have been traced to their hiding-places, their differences established, and their subsequent purity demonstrated, chiefly by their emission and absorption spectra. Three years ago, William Crookes, who had already discovered thallium by the aid of the spectroscope, announced a novel and remarkable extension of the power of this instrument. Crookes found that many substances, when struck by the molecular discharge from the negative pole in a highly rarefied atmosphere, emit phosphorescent light of varied intensity. Having observed under these conditions a bright citron-colored band or line, he pursued the substance producing it, and, after a laborious search, found that it belonged to yttrium. Subsequent studies showed this modification of spectrum analysis to exceed in delicacy all known tests for the rarer earths; yttrium can be detected when present in one millionth part. Within a twelvemonth, Crookes has made known the application of radiant matter spectroscopy to samarium; the delicacy of this test surpasses that for yttrium, and the anomalous behavior of the mixed earths yields phenomena "without precedent."
When Dalton, the Manchester schoolmaster, added to the atomic theory of the Greeks the laws of definite and of multiple proportions, he transformed an "interesting intellectual plaything" into an exact scientific theory capable of experimental demonstration. The importance of ascertaining the atomic weights of the elements with the utmost accuracy has stimulated chemists to apply to the problem their best endeavors; and as the methods of analysis become more refined, the determinations are again and again repeated, every ascertainable and imaginable source of error being carefully eliminated. Besides the experimental repetitions, the figures obtained by various observers have recently been submitted to careful recalculations by Clarke in this country, and soon after by Lothar Meyer and Seubert, in Germany. Their labors give chemists the latest and most reliable constants.
For many years chemists have dimly perceived the probable correlation of the properties of the elementary bodies and their atomic weights. Dumas pointed this out for certain marked groups, Newlands emphasized it; but it remained for a Russian chemist, Mendelejeff, to establish, in 1869, a law of great importance. Mendelejeff showed that if the elements are grouped in the order of their atomic weights, it will be found that nearly the same properties recur periodically throughout the entire series. This so-called Periodic Law is more concisely stated thus: The properties of the elements are periodic functions of their atomic weights. The accuracy of the deductions based on this law is strikingly shown by the fact that Mendelejeff, finding an unfilled blank in the periodic system, boldly announced the general and special properties of the element awaiting discovery; six years later, Lecoq de Boisbaudran discovered gallium, an element which proved to have properties almost identical with those of the hypothetical eka-aluminium described by Mendelejeff. And in 1879 the accuracy of Mendelejeff's prophecy was further confirmed by Nilson's discovery of scandium, the counterpart of the hypothetical ekabor. Eka-silicon, though yet to be discovered, may almost be regarded as a known element, so fully have its properties been predicted.
The correlation between atomic weights and physical properties is being extended, and now embraces the fusibility, boiling-points, general affinities, color, occurrence in nature, physiological functions, and many other factors. Dr. Carnelley, who has been active in developing this subject, at the Aberdeen meeting of the British Association, proposed a "reasonable explanation" of the periodic law; he regards the elements as compounds of carbon and æther, analogous to the hydrocarbon radicals, and suggests that all known bodies are made up of three primary elements—carbon, hydrogen, and æther—an assumption which can not be disproved. In recent years the periodic system has exerted noteworthy influence on the classification of the elements and their compounds. It is of positive utility in determining unsettled questions concerning new and rare elements, and is destined to maintain a lasting hold on chemical philosophy.
The question whether the known elements are truly primary forms of matter has long occupied the thoughts of chemists, and the problem constantly acquires new features. The influence of high temperatures on the spectra of the metals has been a fruitful source of speculations. In 1878 the English astronomer and physicist Lockyer announced the discovery of the resolution of the elements into one primary matter; but when Lockyer's paper was read before the Royal Society his discovery proved to be little more than a hypothesis, and that not a new one, he having been virtually anticipated by Professor F. W. Clarke, of Washington. However, Lockyer's hypothesis was based in part upon experimental evidence. After eliminating coincidences in the lines of the spectra of various metals, due to impurities, so large a number of identical lines remained that he advocated the assumption that these are produced by a primary matter common to the so-called elements. He pointed out that in the hottest stars, Sirius for example, hydrogen only is present, and argued that at extremely high temperatures the so-called elements are broken up into hydrogen, the ultimate matter of the universe. Lockyer's announcement excited, temporarily, a lively interest, but his views are not regarded as supported by sufficient evidence.
More recently, the doctrine of "structure" has been borrowed from organic chemistry, and applied to the elementary bodies; the relations existing between the elements is so similar in many respects to the relations between the hydrocarbons in a homologous series that the elements have been regarded as compounds of carbon with an unknown primary form of matter. Experimental evidence is lacking, but the hypothesis takes a plausible form.
During the past year an Austrian chemist has announced the decomposition of didymium by purely chemical means, and the discovery of praseodymium and neodymium as its constituent elements. An English chemist claims to have evidence of the existence of an allotropic form of nitrogen. Both these statements await confirmation.
The views of chemists concerning the nature of affinity and chemical action are undergoing modifications destined to wield an important influence on the science in the near future. The notion has prevailed, though not distinctly formulated, that the chemical attraction exerted between unlike atoms is a superior sort of cohesion, powerful and absolute; and this force was thought to operate between two elementary bodies directly, without the intervention of a third kind of matter. That this so-called affinity is radically affected by physical state, by heat, and by electricity, has been admitted, but the conviction is growing in the minds of chemists that many circumstances influencing the union and separation of elements have been overlooked; they are beginning to believe that chemical action does not take place between two substances, and that the presence of a third body is important, if not, indeed, indispensable. Many years ago the word catalytic was coined to describe certain isolated phenomena little understood. These phenomena are familiar to chemists, and the number is increasing; the word catalytic is, however, in disfavor, and the term contact-actions is now current. The well-known influence of finely divided and heated platinum in effecting the union of sulphur dioxide and oxygen and the action of metallic silver in decomposing ozone without itself undergoing any change are examples. In these and similar changes one of the substances indispensable to the reaction remains unchanged, and its rôle can not be expressed in equations.
There is another class of reactions in which one body acts upon another only through the aid of a third, which maintains its identity at the close of the reaction, yet is known to be decomposed and recomposed successively throughout the operation. By heating a relatively small quantity of cobaltous oxide with bleaching-powder, the latter is wholly decomposed, yielding calcium chloride, water, and oxygen, yet at the close of the reaction the cobaltous oxide is found unaltered. It has been shown that it is successively decomposed and recomposed during the operation. In their investigation on "Simultaneous Oxidation and Reduction by means of Hydrocyanic Acid," Professors Michael and Palmer consider it probable that many of the most important reactions of animal and vegetable life are due to the intercession of substances which undergo change during the reactions, and in the end return to their original form. They suggest also that some of these reactions seem to be dependent on substances capable of decomposing water into its elements, or into hydrogen and hydroxyl; and, when the chemist can command a reagent possessing that property at a low temperature, their imitation in the laboratory may follow its discovery.
That chemically pure zinc is not soluble in dilute sulphuric acid has been known since Faraday's day; that sodium does not combine with perfectly dry chlorine, even if the metal be heated to its fusing point, was shown by Wanklyn in 1869; more recently, Mr. Cowper has found that dry chlorine does not attack Dutch metal; six years ago, Mr. H. B. Dixon demonstrated before the British Association that a well-dried mixture of carbon monoxide and oxygen can be subjected to the electric spark without exploding. In March, 1885, Mr. H. B. Baker communicated to the London Chemical Society results of his experiments on the influence of moisture in the combustion of carbon and of phosphorus in oxygen, his conclusions being that the combustion of dry charcoal in dry oxygen is incomplete and slower than in ordinary moist oxygen. In the discussion which followed Mr. Baker's paper, Dr. Armstrong pointed out the importance of these new facts in defining more accurately conceptions of chemical action, and suggested that chemical action is "reversed electrolysis." In his address as President of the Chemical Section of the British Association for the Advancement of Science (September 10, 1885), Dr. Armstrong further discussed this subject, and stated that the idea conveyed by the expression "reversed electrolysis" is found in the writings of Faraday, neglect of whose teachings retards the progress of chemistry.
Liquefied ammonia at -65° does not combine with sulphuric acid, but swims on its surface without mixing with it. Donny and Mareska long ago showed that sodium retains its luster in liquid chlorine at -80°, and quite recently Professor Dewar demonstrated that liquid oxygen is without action on sodium, potassium, phosphorus, solid sulphuretted hydrogen, and solid hydriodic acid. He further experimented with other substances normally active, and found their affinity at very low temperatures destroyed.
The speed of chemical reactions is an important factor in chemical theory, the study of which has but recently begun. Wenzel long ago held that the affinity of metals for a common solvent, such as nitric acid, was inversely as the time necessary to dissolve them, and he experimented with small cylinders partly protected by wax. Gladstone and Tribe have made attempts to ascertain the rate at which a metallic plate precipitates another metal from a solution, and they announced a definite law. Professor John W. Langley has since shown that, while their experimental work was correct, their method was faulty, and the results fallacious; he thinks it probable that the true law of chemical action where one metal precipitates another should be thus stated: The time during which one atom replaces another in a compound molecule is constant, and the total rate of chemical action varies directly as the mass of the reacting body in solution.
In his address before the Chemical Section of the American Association for the Advancement of Science, at Philadelphia, Professor Langley discussed the problems of chemical dynamics, and pointed out the rich store of promise in this neglected field. Physics deals with three quantities space, mass, and time. Chemistry has too long been content with studying the changes of matter in terms of space and mass only—that is to say, in units of atomic weight and atomic volume. The discovery of a time-rate for the attractions due to affinity is destined to throw new light on chemical science, and to render it capable of mathematical treatment.
A prodigious amount of work has been done in thermo-chemistry, and within a few years the multitude of isolated observations have been collected, classified, and made available. The importance of this undertaking will be more appreciated in the future than it has been in the immediate past. In all cases of chemical change, energy in the form of heat is either developed or absorbed, and the amount is as definite in a given reaction as are the weights of the substances concerned; hence, measurement of the quantity of heat set free or absorbed in chemical reactions often enables the chemist to determine the true nature of the change. For example, the exact condition of certain bodies in solution can only be conjectured from certain physical characters, few and ill-defined; but by thermic methods of investigation the bodies formed can be accurately ascertained. This is accomplished by reference to the law of maximum work: "In any reaction, those bodies, the formation of which gives rise to the greatest development of heat, are formed in preference to others." Thus the thermometer alone in skillful hands determines the a priori necessity or impossibility of a reaction.
Berthelot, in Paris, and Thorn sen, in Copenhagen, have pursued the subject of thermo-chemistry with indefatigable zeal, and their published results form monuments of exhaustive research. "By the labors chiefly of these two men, we now know the thermal values corresponding to many thousands of chemical reactions. We have learned that the energies of a reaction which can be brought about in two methods, either in the dry way or by solution, differ in the two cases; that salts in solution are in a partial state of decomposition; that the attraction of a polybasic acid radical is not the same for the successive portions of base added, and that the behavior of a monobasic acid in solution differs essentially from that of a dibasic or tribasic acid. We also know that the total energy involved in any reaction is largely influenced by the surrounding conditions of temperature, pressure, and volume."
The interesting border-line between chemistry and physics is an increasing subject of research on the part of both the chemist and the physicist. The periodic press chronicles profound studies of the relations between chemical constitution and the phenomena of diffusion, of capillarity, of dialysis, of dissociation, and of the law of isomorphism. We read investigations on the value of the theory of atomicity, and on the nature of nascent action. Researches in the domain of electrochemistry, especially in connection with the various forms of storage batteries, and in relation to the methods and results of electrolysis, are of such importance as to merit a whole address. The press also records numerous studies in actinometry, of the relations between chemical composition and fluorescence and phosphorescence, as well as of polychroism, and of the results of spectrum observations. Noteworthy are the special applications of optical methods to the determination of molecular structure, viz., the relations between chemical composition and (1) the refractive power; (2), the power of rotating a ray of polarized light; and (3), the absorption spectra of both inorganic and organic bodies.
The meeting of the French Academy of Sciences, held the day before Christmas, 1877, was rendered memorable by the announcement that oxygen gas had been liquefied by two independent experimenters. Previous to that date, hydrogen, oxygen, nitrogen, nitric oxide, marsh-gas, and carbon-monoxide had resisted all attempts to liquefy them, whether in the hands of the skillful Faraday, the ingenious batterer, or the learned Andrews. Physicists and chemists, while admitting the class of so-called permanent gases, had for many years looked forward to their eventual liquefaction, yet the final success came as a surprise. This success was the result of the enterprise and ingenuity of a French iron-master, M. Cailletet, and of a Genevan manufacturer of ice-machines, Raoul Pictet, working independently. In each case, the process consisted in simultaneously exposing the gases to a very high pressure and a very low temperature. Pictet obtained the necessary pressure by generating the oxygen in a wrought-iron vessel strong enough to withstand an enormous strain, and the low temperature was secured by the rapid evaporation of liquid carbonic acid; Cailletet, whose apparatus was marked by extreme simplicity, obtained the great pressure by means of a hydraulic press, and the low temperature by suddenly diminishing the pressure upon the compressed gases. Descriptions of apparatus without diagrams are seldom intelligible; in this place they are superfluous, for we deal with results rather than with methods. Being ignorant of the "critical point" for oxygen, both experimenters employed a much greater pressure than necessary.
Since the initial successes, the problem of liquefying the quondam permanent gases has been successfully attacked by several experimenters, especially by Wroblewski and Olzewski, whose names indicate their nationality. By employing liquid ethylene (which boils in vacuo as low as -150° C. [-238° F.]) as a means of cooling the gases under pressure, both oxygen and nitrogen, as well as atmospheric air, have been liquefied at very moderate pressures.
Among the interesting results obtained are the following: at -102° C. (-152° F.), chlorine forms orange-colored crystals; at -115° C. (-175° F.), hydrochloric acid is a solid; at -118° C. (-180° F.), arsine forms white crystals; at -129° C. (-200° F.), ether solidifies; at -130° C. (-202° F.), absolute alcohol solidifies; at -184° C. (-299° F.), oxygen boils; at -191·2° C. (-312° F.), air boils; at -205° C. (-337° F.), air boils in vacuo. These extraordinary temperatures were measured by means of a hydrogen thermometer and by a thermopile. The lowest temperature measured (to date) is -225° C. (-373° F.), which was reached by reducing the pressure of solid nitrogen to 4 mm. mercury (Olzewski). Further noteworthy results are as follows: Nitrogen was obtained in "snow-like crystals of remarkable size"; the liquefaction of air has been so conducted as to obtain two distinct liquids separated by a perfectly visible meniscus (Wroblewski); and, finally, when hydrogen was subjected to between 100 and 200 atmospheres pressure in small glass tubes surrounded by oxygen boiling in vacuo, it condensed to colorless drops.
These noteworthy results are triumphs of physics rather than of chemistry, but no review of chemical progress can afford to omit them; their bearing on the molecular theory of matter justifies the space given them. It seems probable, moreover, that every known substance on the face of the earth will be eventually obtained in solid form by the mere withdrawal of heat. At these low temperatures the chemical activity of bodies is greatly lessened or ceases, but additional observations must be made on this point before attempting generalizations.
Experiments of the character described demand great resources and are not devoid of danger; those conducting them will be rewarded by undying fame.
The progress of chemistry, in its more material aspects, is characterized by the improved and economic production of known substances, by the discovery and manufacture of entirely new ones, and by novel applications of both these classes as well as of waste materials. The necessity of utmost condensation precludes enumeration of even a centesimal part of the processes and products, nor would the mere catalogue be profitable. Omitting for the present the prolific department of organic chemistry, brief mention may be made of improvements in the metallurgy of nickel (now known to be malleable and ductile), of attempts to cheapen the production of aluminium, of the revival of the barium-dioxide process for manufacturing oxygen on a large scale, of novelties in artistic keramics, of the industrial production and application of the rare metal vanadium, of the successful introduction of water-gas as an illuminating agent, and of constant activity in the fascinating field of photography.
No chemical manufactures are more important than those grouped under the name "alkali industry," which comprises the production of those adjuncts of civilization, carbonate of soda, caustic soda, bicarbonate of soda, and bleaching-powder. Conducted by the methods originated by the ill-fated Nicolas Leblanc, they have, after a century's successful career, begun to give way to a youthful rival. The struggle to maintain the supremacy of Leblanc's process has been severe, the problem being a purely financial one. At first, the profits were made exclusively on the soda; then the decreasing profits, as well as the necessity of condensing the torrents of hydrochloric acid, led manufacturers to add to the production of alkali that of bleaching-powder, and the latter then yielded the profits, while the soda became a by-product. Sharp competition in England and France pushed prices below profitable production, and capitalists with millions involved found their chemical ingenuity severely taxed. Various economical methods of recovering waste by-products were adopted, and finally attention was turned to the "burned ore" or "pyrites-cinders" obtained in roasting pyrites for the sulphuric acid; this is now treated for copper, silver, and, to some extent, for gold. A Spanish company, owning enormous deposits of pyrites on the Rio Tinto, plan to establish in France alkali-works with the intention of deriving their profits solely from the residual oxide of iron and the copper.
Forty-eight years ago alkali manufacturers might have seen a cloud arising, no bigger than a man's hand, which gradually grew darker and heavier, and now threatens to overwhelm the Leblanc process. Dyer and Hemming patented the so-called "ammonia process" for manufacturing soda in 1838; Schlossing and Holland attempted to. carry it out practically in 1855, but it was not found profitable. The credit of overcoming the practical difficulties, and placing the process on an economical basis, belongs to Solvay, of Brussels, who began to manufacture so-called "ammonia-soda" in 1866. Commencing with the modest yield of 179 tons in that year, he increased it in ten years to 11,580 tons, and in 1883 about forty per cent of all the soda made on the Continent was produced by the ammonia process. The success of the new process has completely killed the Leblanc method in Belgium, and has caused the closing of many works in England. A drawback to the new process is that no hydrochloric acid is produced, yet chloride of lime is always in demand; hence a high authority, Dr. Lunge, thinks that in the future the two processes will, of necessity, exist side by side. Mr. Rowland Hazard and others, having secured the right to work under Solvay's patents, have established a manufactory at Geddes, near Syracuse, New York. The estimated production of these works for 1886 is thirty million kilos, and the soda obtained is of great purity. It will be interesting to watch the future of this industry in America.
In modern chemical literature by far the greatest amount of space is occupied with researches and discoveries in organic chemistry. To the non-professional reader the peculiarly technical language, abounding in words of unusual length, is not only incomprehensible, but positively forbidding. A vocabulary which contains such terms as toluyldiphenyltriamidocarbinol acetate and methylorthomonohydroxybenzoate does not encourage the casual reader; and when he learns that the first-named body is the dye-stuff commonly called magenta, and that the second is the innocent oil of wintergreen, surprise gives way to feelings of despair. When one is gleefully informed that a distinguished foreigner has discovered that orthobrombenzyl bromide treated with sodium yields anthracene, which, heated with nitric acid, yields anthraquinone, and that anthraquinonedisulphonic acid fused with potassium hydroxide furnishes dioxyanthraquinone, the lay hearer can hardly be expected to become enthusiastic over the announcement, and yet these operations conducted in the private laboratory of a man of genius have been of direct benefit to mankind, setting free thousands of acres for the production of breadstuff's, and establishing industries employing a multitude of workmen. In a word, these abstruse phrases describe the artificial production of alizarine, the valuable coloring matter of madder.
The polysyllabic nomenclature now prevailing expresses to the chemical mind the innate structural composition of the body named; of late years the words are formed by joining syllables to an almost indefinite extent, and a distinguished chemist has recently urged the advantages of empiric names in place of the unwieldy system. Whether Dr. Odling's plea will produce a reaction in favor of empiric names remains to be seen.
To enter into details concerning the recent progress of organic chemistry, and to make them intelligible to an audience not composed of well-read professional chemists, is an undertaking of doubtful success; we shall content ourselves chiefly with generalities.
That remarkable product of nature, petroleum, continues to occupy the studies of chemists at home and abroad. Newly invented methods of fractional distillation have disclosed previously unsuspected constituents and peculiarities. Lachowitz has found in the petroleum of Galicia several members of the aromatic series; Mendelejeff has noticed abnormal relations between the specific gravity and boiling-points of successive fractions in distilling American petroleum. The various commercial products from crude petroleum, rhigolene, vaseline, paraffin, etc., continually find new and useful applications, their names being household words.
The industrial and scientific novelties in the important groups of oils and fats, alcohols, and acids, can not be specified. After cane sugar, glucose is receiving the most attention; in the United States and Germany are sixty manufactories of the various grades of starch sugar, the annual home production alone being valued at ten million dollars. Glucose is extensively used as a substitute for cane-sugar in the manufacture of table-syrup, in brewing, in confectionery, in making artificial honey, and in adulterating cane-sugar, as well as in many minor applications. Recent experiments by Dr. Duggan, of Baltimore, show that glucose is in no way inferior to cane-sugar in healthfulness. Much work has been done on sorghum by Dr. Peter Collier, and the first complete examination of maple-sugar has lately been made by Professor Wiley, of the Department of Agriculture. Lovers of the latter sweet will be pleased to learn that it can be made by adding to a mixture of glucose and cane-sugar a patented extract of hickory bark which imitates the desired flavor.
The great demand for high explosives as adjuncts to engineering, mining, and military operations, occasions constant experimentation; besides the invention of mere empiric mixtures of known substances, chiefly nitro compounds, much work is done of a purely scientific nature, such as investigations on the chemical reactions and products of explosive mixtures, on the heat disengaged by their explosion, on the pressure of the gases produced, and on the duration of the explosive reaction. Thanks to the "Notes of Professor C. E. Munroe, of the United States Naval Academy, chemists are informed of the freshest novelties in this department, rendering further mention superfluous.
The researches of chemists in the aromatic series outweigh in both number and importance those in all other sections. The once despised refuse coal-tar has created an entirely new chemistry, and, in its products and derivatives, is by far the most promising field for investigators. The compounds of the aromatic series have afforded some of the most notable successes in synthetical chemistry, as well as some of the most useful substances for dyeing, for hygienic and medicinal purposes. The oil obtained in the dry distillation of bones, a subject of classic investigations by Anderson, of Glasgow, forty years ago, has recently acquired new interest; one of its constituents, pyridine (C6H5N), has been obtained in several ways which show that it bears the same relation to certain acids derived from natural alkaloids, such as quinine, nicotine, etc., that benzene does to benzoic and phthalic acids. These facts point to the possible artificial preparation of quinine at no distant day. This view of the constitution of the alkaloids is confirmed in many ways, notably by Ladenburg's discovery that piperidine, a base occurring in pepper, is hexahydrobenzene.
Professional chemists also acknowledge the marvelous success in unraveling the complications of isomerism, and the important aid afforded the study of isomeric bodies of the aromatic group by the doctrine of orientation. These rather technical details can receive, however, but brief mention, though a whole series of lectures could be devoted to the fascinating topic. Leopold Gmelin, when writing his "Hand-book of Chemistry," in 1827, requested organic chemists to stop making discoveries, or else he could never finish! And during the sixty years which have elapsed the activity in organic chemistry has been unceasing; yet the extraordinary number of facts now known is not so great as those which the prophetic eye sees disclosed by recently revealed lines of investigation.
The crowning glory of chemistry is the power of producing, in the laboratory, from inorganic matter, substances identical with those existing in the vegetable and animal kingdoms. Belief in the mysterious vital force operating in living beings received a rude shock at the hands of Wohler, sixty years ago, and successive triumphs in synthesis have dispelled it entirely, so far as non-organized bodies are concerned: "To-day we know that the same chemical laws rule animate and inanimate nature, and that any definite compound produced in the former can be prepared by synthesis as soon as its chemical constitution has been made out." Within a few years chemists have announced the synthesis of many acids, essential oils, alkaloids, glucosides, dye-stuffs, and other bodies naturally occurring in the organic world, and so rapidly do these announcements succeed one another that expectation has displaced surprise. Noteworthy are the following: Alizarine, the valuable coloring-matter of madder; vanilline, the aromatic principle of the vanilla bean; cu marine, the aromatic principle of the Tonka bean; indigo, the well-known dye-stuff; uric acid, an animal product; tyrosin, likewise a product of the animal organism; salicine, daphnetine, and umbelliferone, natural glucosides and related bodies; piperidine, a constituent of pepper; and cocaine, the new anæsthetic. Besides these, many syntheses have been accomplished of bodies isomeric and not identical with the natural products.
The alchemists labored to transmute base metals into noble ones, and were destined never to realize their ambitious designs; modern organic chemists, operating on substances compared with which even the base metals are precious, produce articles more beneficial to mankind than gold itself, and, at the same time, gain, indirectly, no small store of the coveted metal.
The application of chemistry to physiology encounters the most complex and difficult problems in the science, and at the same time aims to accomplish the most beneficent results. "The physiologist complains that probably ninety-five per cent of the solid matters of living structures are pure unknowns, and that the fundamental chemical changes which now occur during life are entirely shrouded in mystery. It is in order that this may no longer be the case that the study of carbon compounds is being so vigorously prosecuted." It may seem strange to the non-professional in this audience that, in spite of persistent and skillful attempts to solve the problem, chemists are obliged to admit ignorance of the exact composition of so common a substance as the white of egg; yet, until they acquire an accurate knowledge of the constitution of albuminous substances, the processes of animal economy can not be explained. While the physiologist, in some degree, waits on the organic chemist for further developments, the latter discovers and prepares novel bodies much faster than the physiologist ascertains their influence on the animal economy. To the joint labors of chemists and physiologists are due the blessings of anæsthetics, hypnotics, and other conquerors of suffering and disease. The anæsthetic properties of cocaine, and the circumstances of their discovery, are matters of popular knowledge. Within a twelvemonth, ethyl-urethane has been added to the list of hypnotics.
In recent years sanitary chemistry has acquired great importance, and now occupies a distinctly defined field, including all that pertains to the hygienic value of foods and beverages, their adulterations, and their fraudulent substitutes; questions of gas and water supply; of the uses and abuses of disinfectants; of household ventilation, and of the diverse matters grouped under the term chemical engineering. Of this very practical branch of chemical science, as well as of the valuable additions to materia medica, of the improved methods introduced into analytical chemistry, and of the contributions to the chemistry of agriculture, no mention can be attempted.
The tendency of modern researches in chemistry is to magnify the atomic theory; the rapid accumulation of facts, the ever-increasing ingenious hypotheses, the most searching examinations of co-ordinate laws, all tend to strengthen the Daltonian adaptation of the philosophic Greeks. Here and there a voice is raised against the slavish worship of picturesque formulae; but, against the molecular theory underlying the symbolic system so depicted, few earnest arguments are advanced. The whole aim of organic chemistry is directed to the discovery of the arrangement of atoms within the molecule, and the success Obtained justifies the hypothesis. The edifice erected through these achievements, though young in years, is too substantial to tolerate displacement of its corner-stone. The absolute truth of the atomic theory is beyond man's power to establish; even admitting that it necessitates absurd assumptions, it is, nevertheless, indisputably the "best existing explanation of the facts of chemistry as at present known."
A noteworthy feature of existing chemical research is the recognition of the necessity of a more intimate knowledge of the connection between physical characters and chemical constitution. In the past chemists increased the number of new compounds so rapidly that they often neglected detailed examination of their physical properties, their relations to known bodies and to each other, preferring to satisfy their ambition by fresh discoveries. This race after new bodies still continues, but parallel with it are zealous investigators striving after a knowledge of the innate qualities and bearings of these same bodies; and the latter class of students is gaining prizes no less valuable than those secured by the former.
Chemists are also recognizing the necessity of a more minute study of the simpler phenomena of chemistry, and it is in this direction that they look for many laurels in the future. Priestley's day of great discoveries by the simplest means has in one sense passed; the opportunities for isolating nine new gases, or of recognizing by chemical tests half a dozen new elementary bodies, in the space of a lifetime, are gone; only by the employment of the most delicate appliances, by the closest scrutiny of phenomena and the conditions governing them, by availing themselves of all the resources of physics, by an unshrinking expenditure of time and of money, to say nothing of the necessity of trained mental powers of no low order and of skilled hands, shall chemists in succeeding generations realize their ambitious designs.
- From an address read before the New York Academy of Sciences, March 15, 1886. Revised by the author.
- Estimated. Many chemists are members of several of the above societies, but against this duplication may be set those not connected with societies.