THE NEWEST-CHEMISTRY

Evening Star, Issue 16092, 18 April 1916, Page 7

THE NEWEST-CHEMISTRY

—Mechanism 'and Chemistry.—

[By James Collier.]

[Special"Rights Secured by the 'Star.']

Some 40 years ago an eminent transatlantic professor, Dr Cooke, contributed to the International Scientific Series a volume entitled 'The New Chemistry,' and if my memory does not mislead mo it had been anticipated in a volume with the same title published by Dr E. L. Youmans. Now a treatise with a similar title, slightly varied, has been issued by a third American professor, Professor Harry Jones, of Johns Hopkins University at Baltimore, and it seems to be called for as a record of researches and discoveries that parallel ihose of any previous period. ' A New Era in Chemistry' it is named, and a new era in chemistry it appears to be

—Law of Mass-Action.—

It consists of isolated or independent advances made by a succession of chemists between 1865, when Berthelot began his series of thermochemical investigations, to the discoveries of Van't Hoff and Arrhenius about 1887, and the organisation of these into a system by Ostwald in subsequent years. The first notable advance within our period was the discovery of " the law of mass-action " by two professors in the University of Christiania—the Norwegian physicist, Gnldberg, and his son-in-law, Waage, the chemist. (The relationship of the joint, discoverersi~reminds us of the discovery' made a few weeks ago by Professor Brags;, late of Adelaide, and his son.) The two took up a research on the effect of massaction in chemistry. They studied n number of chemical reactions t experimentally, and found that " the velocity of a chemical reaction is proportional trs the mass of the substances reacting." And they packed up the result of many experiments into a neat little algebraic formula. If this law is applied to the equilibrium of reactions, the condition of equilibrium is attained when two opposite reactions _ acquire equal velocities. And another little algebraical formula, consisting of three letters and four signs, holds months of labor in solution.

Not for long were these results, arrived at in 1867 and buried in a university program," made known to the chemical world at large. What good thing could come out of Nazareth? What original idea out of Christiania? The verv thing that now recommends the formulaits algebraic expression—was against it then. Nor was it in its favor that it was so simple. Yet it is now held to be " one of the fundamental generalisations on which the- newer developments in chemistry rest." So a Johns Hopkins University chemist, Professor Harry Jones, asserts, and so we may find it to be.

—Chemical Reactions And Energy

Changes,—

A second great generalisation was made by the French chemist, Berthelot. After chemists had studied the changes in matter that accompany chemical reactions, they devoted themselves to the accompanying changes of energy. Thev had looked on the material transformations as the more important. Now they began to see that the changes of energy are the really > important things, and tfiat the material changes are subordinate. The pioneer work in this line was done by Julius Thomsen, of Copenhagen, and Mess, with their work on thermochemistry. Berthelot was the first to discern the importance of the study of the energy-changes that cause all chemical action. Ke discovered the law of maximum heat-evolution and made of it a grand generalisation. It is in effect: "Of several possible reactions between two or more substances that one will taie place which liberates the largest amount of heat." .As already stated in these columns, he connected chemical action with thermal change. It was a step and a stride, a leap and a bound in advance.

—Stereochemistrv.—

A third generalisation was made by Van't Hoff, who was born at Rotterdam in 1852. Dissatisfied with the theories of Kekule, who made great advances in organic chemistry, but did not arrive at quantitative results, Van't Hoff aimed at determining the geometrical arrangement of atoms within the molecule. Here Pasteur (as already stated in these articles) did pioneer work by showing that optical activity is caused by some kind of asymmetry, but he was ignorant in what the asymmetry consisted. Two savants discovered it simultaneously—Van't Hoff in September, 1874, and a French chemist in November of the same year. Le Be] showed that the asymmetry is that of the chemical molecule.: More than this: he ascertained that «every optically active substance contains a carbon atom combined with four different atoms or groups. A few weeks earlier young Van't Hoff laid the foundations of stereochemistry, or chemistry in three dimensions. If the carbon atom at the centre of tho group was in combination with all four atoms or groups, the molecule would be unsymmetrical. Lo Bel had arrived at the " tetrahedral carbon atom " : Van't Hoff crowned it by exhibiting the asymmetrical tetrahedral carbon atom. This discovery made possible a science of quantitative chemistry in three dimensions. Tt turned the main current of organic chemistry. It has ever since been the controlling'power in that science. Van't Hoff, however, did not, any_ more than Kekule, arrive at quantitative results. This final step was taken by Gye, who proved that a quantitative relationship between the asymmetry in the case of any given compound and its optica] activity can be established. But the demonstration is far too technical for these columns. Still, the fact has been demonstrated, and Spencer's view, that a branch of knowledge becomes a science when it becomes quantitative, is confirmed.

—The Gibbs Phase Rule.—

A third generalisation has plaved a huge, though still questioned, part'in the recent developments of chemistry. It was discovered by Professor Willard" Gibbs, of l:ale. and bear? tho same impress as nearly allthe most-modern chemical advances. It is half physical and half chemical. It seeks, the solution of chemical problems byphysical agencies. Briefly, it shows "how, by thermndynamical methods, the conditions of chemical eou-ilibnum can be systnvatinsllv grouped." It is the universally ki.own Phase Rule. ' 'These conditions -ire expressed'in terms'of the relations between the phases and the- comnonenta. A phase is a modification of a substance. Almost every chemical substance exists In three phases—solid, liquid, and vapor. Some, as sulphur, exist in four, two being solid. A component can vary independently. The three independent variables are coii--eentration, pressure, and temperature. How shall wo find, in any given case, the stable phase? Ascertain'the curve mado bv the temperature and pressure jointly, and in the case of, say. water the'vaporous is the stable phase to the right and below the curve, while the liquid i? th» stnbte phase to the left above, the curve. This is the simplest- case of equilibrium, but it- will show the value of the method. For some years the research lay buried in tho transactions of a local scientific fociety in the United States. Then its value was perceived by a Dutchman. Van der Waals, and the memoirs containing it were translated, into German dv the indefatigable Ostwald. A second German. Roozehoom. and n. third." Vnn't-Hoff. experimentally applied Gibhs's 'equations. From them, savs Jones, new relations have been discovered, new compounds detected, and new lines of work opened out. The Ceneralisation and its applications have brought Gibbs a world-wide fame. —Chemical Dynamics and Chemical Equilibrium. —

A fourth generalisation is that of Van'fc Hoff, and it is called the " principle of mobile equilibrium." Following Horstmann-, who 'introduced thermodynamfcs into chemistry, he endeavored to apply thermodynamics to chemical problems, and this led him to the famous principle jugt named. That indicates the relations between the change of the conditions of a system and the nature of the processes brotifrht about bv thes* chances. . By this generalisation Van't Hoff "threw light on the entire field. of chemical dynamics and statics," says Jones, and Oatwald say» that the magnitude of the influence it has exercised, on all later work cannot yet be properly eetimatod.

A fifth generalisation was the achievement of a French chemist whose nam© was laWy mentioned in llsssn columns. Le Chitelier showed that equilibrium., in chemistry is amenable to the same laws as in physics and mechanics. He applied to chemistry the mechanical laws that action and reaction are equal and opposite; he similarly showed the effect of a change of temperature, as also the effect of pressure and condensation, itnd he proved the analogy between chemical arid mechanical equilibria, yielding a law of equivalence. In genera], ho laid great sti\?sg on the analogies, and the new departure is important because the laws of mechanics are susceptible of mathematical treatment. So, therefore, are those of chemistry, as Guldberg and Waage proved.

—Solutions and Gases.--

A sixth and still greater contribution to chemistry was Van't Hoffs discovery of the relations between solutions and gases, or osmotic pressure and gaseous pressure. Osmotic pressure is a hypothetical force that drives a aubstance from the region of greater to that of less concentration. In 1877 I'feffer had successfully measured osmotic pressure in the case of & few substances and over a limited range. But, as Emerson eays is the way with genius, which reels off a tune from a few bars, from these meagre and imperfect data Van't Hoff discovered the- relations between osmotio pressure and gaseous pressure. .. In a brief memoir of 28 pages he contributed a classic to the literature of chemistry. He finally formulated the laws of Boyle and Gay-Lusea-c as applied to solutions. —Electrolytio Dissociation.-

Van't Hoff had, however, failed to explain the exceptions to his law presented by tho elactrolvtes, or the acids, bases, and Ealts, which are by far tho most important of chemical compounds. A young Swedish 'chemist, Arrlienius, took up the problem where tho Dutch master had dropped it. He was then only 28 years old, and a lecturer at the High School of Stockholm, which was eoon to be created tho University of Stockholm. Like Van't Hoff, he was subsequently offered'a Chair at the University of Berlin, but declined it. He was afterwards awarded the Nobel Prize. A succession of great chemists had grappled with the problems of electrolysis. Grotl-huss, in 1806. was the firnt to propound a theory that accounted for the then known phenomena, and hie theory prevailed for half a century. He was followed in 1851 by Williamson-, who proposed n theory of solutions. In the same year Clausius enunciated a theory which, if rot in itself the whole truth," at least suggested a true view. In 1885 Arrhenius converted the qualitative suggestion oi Clausius into n, quantitative theory, laiown as the 'dissociation theory. The gist of it is that " those substances which are chemically the most! active are tho most dissociated," The theory connects dissociation and chemical activity. Tho dons, as Faraday called them (or {'he electrically charged p&rts of molecules). are the most active chemical agente. The theory was the outcome of Van't B'off's discovery of the relations bct.voen solutions and gases. It coordinates and correlates facts already known, prjdicts new facts since discovered, suggests original lines of work, and fir ally places chemistry on a eound mathematical and physical basis. Its further development is striking. Sir J. J. Thomson first explained substitution in chemistry as puivly an electrical act. —Solvate Theory of Solution.— '

In 1899 a. Japanese, JCenjira Ota, went to the United States, and. there, in conjunction with Professor Jones and eifiht of his students, worked at between 4,000 and 5,000 solutions, and developed and supplemented the generalisations of Van't Hoff and Arrhenius; with the theory of solvation in solution they arrived at a satisfactory theory of solutions in general. All chemistry was thus found to be a branch of tho science of solutions . Virtually, all true chemical reactions t-ako place in solution.