392 SCIENCE PROGRESS. 



chemical behaviour, led to the formation of mixed crystals. 

 For example, the molecular weight of quinoline is normal 

 in benzene, but abnormal in naphthalene ; acridine gives 

 a normal value in benzene, but an abnormal value in 

 phenanthrene. Such observations may be used to throw 

 light on the chemical constitution of dissolved substances. 

 Nicotine, for instance, unlike y-dipyridyl, does not form 

 mixed crystals with diphenyl, consequently the constitution 

 of nicotine, which is at present undecided, is probably 

 of a different type from that of y-dipyridyl (Garelli, 

 Ciamician, 1894). 



j. W. Rodger. 



[To be continued.) 



