MOLECULAR DISSYMMETRY 



23 



Before leaving this subject let us point out a last series 

 of facts and conclusions. Tartaric acid and malic acid 

 undergo changes due to the action of heat; the former 

 gives pyrotartaric acid, the second maleic acid and a fum- 

 aric acid identical with that which is derived from the 

 fumitory. Is the atomic grouping which gives to the 

 tartaric and malic acids the property' of acting on polar- 

 ized light preserved intact in their derivatives? Experi- 

 ment shows that this is not the case. All these acids, 

 pyrotartaric, maleic, fumaric, and their salts are inactive. 

 According to Pasteur's interpretation, the molecules of 

 tartaric acid, aspartic acid and malic acid, are dissym- 

 metrical; those of the pyrotartaric, maleic, and fumaric 

 acids are not: the atoms are differently grouped and a 

 new proof is this, that the. two tartaric acids, the right- 

 and the left-handed, give only a single pyrotartaric acid. 



VI 



MOLECULAR DISSYMMETRY 



The moment has come to pursue more closely than 

 we have hitherto done these ideas of dissymmetry. 



Fig. 4. Diagrams illustrating molecular dissymmetry. 



There is a fundamental difference between the hemihedral 

 forms coming from the cube, as in boracite, or from 

 the hexagonal prism, as in Iceland spar, and the 

 hemihedral forms realized in the tartrates. All the 



