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the left-handed crystals left-handedly. These solutions yielded on 

 evaporation, the one only right-handed, the other only left-handed 

 crystals. The crystals of the two salts were purified by recrystalliza- 

 tion, their acids isolated, and the chemical, optical, crystallographic, 

 and pyroelectric properties of the acids themselves or their salts or 

 solutions carefully compared. A like comparison was instituted 

 between these acids and the well-known tartaric acid. The acid 

 obtained from the right-handed crystals proved to be absolutely 

 identical with tartaric acid in all its properties, that obtained from 

 the left-handed crystals proved to be identical, so to speak, with the 

 image of tartaric acid in a mirror, the two acids absolutely agreeing 

 in all their properties except as to right-handedness and left-handed- 

 ness. Where the one acid yielded crystals hemihedral right-handedly, 

 the other yielded crystals exactly similar, except that they were 

 hemihedral left-handedly ; where the one yielded a solution rotating 

 the plane of polarization right-handedly, the other yielded a solution 

 rotating it left-handedly to the very same amount, and with the very 

 same peculiar dispersion of the colours. On mixing equal quantities 

 of the acids from the right-handed and left-handed crystals, racemic 

 acid was reproduced. 



Stimulated by this remarkable discovery, M. Pasteur has continued 

 his labours in the same direction, and the results which he has since 

 obtained are given in a series of papers published in the 'Annales 

 de Chimie,' and extending nearly to the present time. 



Hitherto no "active" substance (i, e. one whose solution has the 

 power of rotating the plane of polarization of polarized light) has 

 been obtained artificially from inactive substances, except in the case 

 of the splitting up, or at least separation, of racemic acid into a right- 

 handed and a left-handed substance ; and this law seems worthy of the 

 attention of chemists who attempt the artificial formation of the 

 organic alkaloids. This law would have been violated had two acids 

 which chemists had obtained from fumaric acid, an inactive substance, 

 and which appeared to be identical with aspartic and malic acids 

 respectively, been really so. But M. Pasteur found that these acids 

 were inactive, unlike aspartic and malic acids, from which they also 

 differed in some other respects. 



The two acids obtained from racemic acid were found to be iden- 

 tical in their properties (except as to right-handedness and left- 



