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

  • Louis Pasteur
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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    differences. Let us imagine a right screw and a left screw separately penetrating two identical blocks of wood with the grain straight. All the mechanical conditions of the two systems will be the same. This will no longer be so from the moment that the same screws are associated with blocks which are themselves twisted in the same sense or in the opposite sense. X. , Here is a very interesting application of the facts which have just been explained. Seeing that the right and left tartaric acids formed such dissimilar compounds simply on account of the rotative power of the base, there was ground for hoping that, from this very dissimilarity, chemical forces might result, capable of balancing the mutual affinity of the two acids, and thereby supply a chemical means of separating the two constituents of paratartaric acid. I sought long in vain, but finally succeeded by the aid of two new bases, quinicine and cinchonicine, isomers of quinine and cin- chonine, which I obtained very easily from the latter without the least loss. I prepare the paratartrate of cinchonicine by neutralis- ing the base and then adding as much of the acid as was necessary for the neutralisation, I allow the whole to crystallise, and the first crystallisations consist of perfectly pure left tartrate of cinchonicine. All the right tartrate remains in the mother liquor because it is more soluble. Finally this itself crystallises with an entirely different aspect, since it does not possess the same crystalline form as the left* salt. We might almost believe that we were dealing with the crystallisation of two distinct salts of unequal solubility. * [ Right in original.]