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Abstract.
The author sketched briefly the older radical and type theories, showing how each failed to lay sufficiently bare the internal structure of the molecule. The chain theory was then gone into at some length, and its inability to explain many well-known cases of isomerism pointed out. Having thus made evident the necessity for widening the theory, the author proceeded to explain the stereo-chemic hypothesis of Le Bel and van't Hoff. By help of models, the possible derivatives of a single carbon and the combinations of two such systems were developed, it being thus shown how two hitherto unknown classes of isomers were rendered possible—viz., those due to the presence of asymmetric carbon-atoms, and those due to the presence of doubly-bonded pairs of carbon-atoms. Many examples from organic chemistry were then given in support of the hypothesis, special stress being naturally laid on those compounds (e.g., tartaric acid, amygdalic acid, malic acid, propylene glycol, amylic alcohol, camphor, &c.) whose optical activity was not dependent on the solid state. In conclusion, attention was drawn to the fact that the stereo-chemic method had already been extended to other elements, notably nitrogen and oxygen; that it had done much service in the development of organic rings, had explained in a very satisfactory manner several hitherto abnormal anhydrides and oximes, and bade fair to be of considerable use in comparing the chemical energies of the several members of any special group.
Sir James Hector complimented the author on his splendid paper. He hoped that before long the services of Dr. Evans would be secured as a teacher in one of our colleges. He pointed out how necessary it was for Wellington to have a college where a lecture of this kind would be of much benefit to students, and he hoped Dr. Evans would on a future occasion give the Society further experimental proofs of the theories he advanced.
Mr. Hulke said he had listened with great pleasure, for the subject of the paper had been for some time past of great interest to him. If there was any foundation of truth in the theory, then the polariscope would be to the chemist what the spectroscope was to the astronomer. All innovations met with opposition. When, half a century ago, the increasing
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number of organic compounds necessitated a revision of chemical nomenclature, Dumas tried hard to stop the change. He sneered at constitutional formulæ, and the designation of compounds by their common-sense names. And so with the new theory. Its authors were ridiculed by some of the greatest chemists of the day. Because Wisliceuns favoured it Kolbi attacked him in no measured terms, accusing him of quackery and charlatanism akin to spiritualism; and now Kolbi is gone, and Wisliceuns sits in the professorial chair formerly occupied by his bitter opponent.
Dr. Evans, in reply, said that unfortunately very few experiments connected with stereo-chemistry had much attraction for any one but a chemist, and nearly all demanded a much longer time than that placed at the disposal of a lecturer. With regard to the remarks of the Chairman on the relations between optical activity and living organisms, he might say that such a connection had been almost conclusively proved not to exist. The special acid mentioned by Sir James Hector—namely, tartaric acid—had been synthetically produced in all its modifications; and these had proved themselves the exact counterparts of those derived in the usual manner from the juice of the grape. Many other optically-active substances had also been synthesized with like results. Moreover, all attempts to bring about optical activity by means of ferments and other living organisms, in fluid whose molecules did not possess asymmetric carbon systems, had resulted negatively.