Researches on the molecular dissymmetry of natural organic products : presented to the Chemical Society of Paris, January 20 and February 3, 1860 / by L. Pasteur ; translated from "Leçons de chimie professées en 1860" by W.S.W. Ruschenberger.

  • Pasteur, Louis, 1822-1895.
Date:
[1862]
Catalogue details

Licence: Public Domain Mark

Credit: Researches on the molecular dissymmetry of natural organic products : presented to the Chemical Society of Paris, January 20 and February 3, 1860 / by L. Pasteur ; translated from "Leçons de chimie professées en 1860" by W.S.W. Ruschenberger. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    auction and in the anticipation even of the results which I am L 'have the honor to lay before you, that I immediate y made a iourney to Vendome, where I submitted my doubts to 1 Dessaignes, who at once presented me with a specimen of his aspartic acid. On my return to Paris, I found ^mediately, in fact, that the acid of M. Dessaignes was only an isomeric ot the natural aspartic acid, that is, the acid derived from aspara- gine, and that it differed from it, as I had foreseen, by the rotary property, entirely absent in the artificial acid, not at all doubt- ful in the natural acid. But all the other physical and chemi- cal properties possessed the greatest analogies, so great that M. Dessaignes, who was not put on his guard by any pre-conceived idea, had concluded that the two substances are really identical. What attracted me most in the examination of the new com- pound, (which by itself offers no very remarkable crystallizable combinations,) was its transformation into malic acid. It is indeed known that M. Piria, just mentioned, long ago gave the means of obtaining malic acid from asparagine and aspartic acid; and I was assured by the most exact proofs that this malic acid was identical with that of the service, [sorbus,] the apple, the grape, and tobacco. I then treated the new acid in the manner discovered by M. Piria, and transformed it into a new malic acid very similar to the natural acid, so close to the latter, that a chemist would have great difficulty in distinguishing them, even if warned of their real dissimilarity; only this malic acid had no action on polarized li^ht, and it was the same with all its saline combinations. There are certain derivations of these two malic acids, the comparison of which does not very clearly manifest the true mu- tual dependence of the molecular arrangements of these curious isomerics, but there are others in which it is plainly seen. Let us consider, for example, the ordinary active bimalate of lime, and the corresponding inactive bimalate. Their chemical com- position is exactly the same, and their crystalline forms are alike, ^yith this difference that the form of the active bears four small hemihedric faces, always absent in the form of the inactive. Whence it results that placed before a glass, the image of the active cannot be superposed on it, while the image of the inactive is absolutely identical and superposable to the reality which gives