148 MOLECULAR GROUPING 



Tammann 1 with platinum double cyanides, whose com- 

 position can vary between MgPtC 4 N 4 6-25 and 6'8H 2 O 

 without loss of crystalline form. 



B. Orientation of the Molecules in the Crystal. 



j. Relations between Symmetry in the Crystal 

 and in the Molecule. 



Since the application of the methods for determining 

 molecular weights to solids (p. 70) has made it highly pro- 

 bable that the solid state is not characterized by the con- 

 dition of complex molecules, the way is open to bring the 

 configuration of molecules, as already developed (p. 90), 

 into relation with crystalline form, and especially with the 

 arrangement of molecules in regular point systems (p. 141) 

 which give a plausible molecular-mechanical explanation 

 of that form. 



We may first mention what, of such researches, refers 

 to the relations of symmetry in the molecule and in the 

 crystalline structure. The leading result is the necessary 

 conclusion pointed out by Pasteur, that a whole made up 

 of similar asymmetric molecules cannot possess symmetry. 

 What in his time could not be sharply formulated has since 

 the development of stereochemistry become immediately 

 clear 2 . Consider as unsymmetrical grouping such as one 

 assumes on presence of an asymmetric carbon atom, e. g. in 

 ammonium bimalate : 



COOHCH 2 CHOHCOONH 4 , 



in which the four different atomic complexes or atoms, 

 COOHCH 2 , H, OH, COONH 4 , are thought of as in tetra- 

 hedral arrangement round the carbon atom distinguished 

 by underlining (Fig. 16, p. 105); a regular arrangement of 



1 Buxlioevden and Tammann, Zeitschr. f. anorg. Chem. 1897, p. 319; 

 Wied. Ann. 1897, p. 16. See also Riniie, Neues Jahrb. Mineral. 1899, I. p. i ; 

 Joannis, Comptes Rend. 109. 965, no. 238. 



3 Becke, Min. u.petrogr. Mitteilungen von Tschermak, 10. 414, 12. 256. 



