Researches on the molecular asymmetry of natural organic products / by Louis Pasteur (1860).

  • Pasteur, Louis, 1822-1895.
Date:
1905
Catalogue details

Licence: Public Domain Mark

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

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    the plane of polarisation is common to both, but the character of the phenomenon is quite different. Thus quartz deviates; but it must be crystallised. Dissolved, or solid and not crystallised, it lacks the property. Not only must it be crystallised, but it must be cut in plates perpendicular to the axis. As soon as the plate is slightly inclined to the direction of the ray, the effect is diminished and finally disappears. Sugar deviates (and what is said of sugar is true of all the other organic products), but the sugar must be dissolved, or solid and amorphous as in barley-sugar. In the crystallised state it was impossible to discover any effect. The tube containing the solution of sugar may be inclined. The deviation does not alter for equal thick¬ nesses. And, what is more, active agitation of the liquid by means of clock-work leaves the phenomenon the same. So that, from the first, Biot quite definitely concluded that the action produced by the organic bodies was a molecular one, peculiar to their ultimate particles and depending on their individual constitution. In quartz the phenomenon is a consequence of the mode of aggre¬ gation of the crystalline particles. These are the physical precedents, if I may so express myself, for the researches which I am about to lay before you. We must next consider their mineralogical pre¬ cedents. II. Hemihedry is certainly the one of the peculiarities of crystallisation which is most easily grasped in its external manifestation. Consider, for example, a mineral species crystallising in the cubic form. This species can show, as everyone knows, various kinds of forms determined by