Researches on the molecular asymmetry of natural organic products (1860).

  • Pasteur, Louis, 1822-1895.
Date:
1905
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Licence: In copyright

Credit: Researches on the molecular asymmetry of natural organic products (1860). Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    products which possess the molecular rotative property, have hemihedral crystalline forms, an idea which had not previously occurred to any one in spite of Herschel's correlation. This investigation met with the success which I anticipated. I also occupied myself with the examination of the crystalline forms of paratartaric acid and its salts. These substances are isomeric with the tartaric compounds, but had all been found by Biot to be inactive towards polar- ised light. None of them exhibited hemihedry. Thus the idea of the inter-relation of the hemihedry and the molecular rotatory power of natural organic products gained ground. I was soon enabled to establish it clearly by a wholly unexpected discovery. IV. I must first place before you a very remarkable note by Mitscherlich which was communicated to the Academic des Sciences by Biot. It was as follows :— The double paratartrate and the double tartrate of soda and ammonia have the same chemical composition, the same crystalline form with the same angles, the same specific weight, the same double refraction, and consequently the same inclination in their optical axes. When dissolved in water their refraction is the same. But the dissolved tartrate deviates the plane of polar- isation, while the paratartrate is indifferent, as has been found by M. Biot for the whole series of those two kinds of salts. Yet, adds Mitscherlich, here the nature and number of the atoms, their arrangement and distances, are the same in the two substances compared. This note of Mitscherlich's attracted my attention forcibly at the time of its publication. I was then a B