ORGANIC CHEMISTRY 197 



The chloride of the 2 : 6'-dinitro-diphenic acid [XII] on 

 treatment with hydrazine gives a hydrazide [XIII], although 

 on hydrolysis it regenerates the original acid 



COCl NO2 



o — o 



coci \ / 



CO CO 



NH— NH 

 [XII] [XIII] 



it is not clear, however, whether this compound is identical 

 with the analogous one prepared from 6 : 6'-dinitro-diphenic 

 acid ; if so, inversion has taken place apparently under the 

 influence of hydrazine. 



The further study of diphenyl compounds should yield 

 results of interest and may suggest an alternative explanation 

 to that of Cain which is not entirely satisfactory. The per- 

 sistence of the isomerism under drastic chemical change and 

 the apparent failure to convert one isomeride into the other are 

 phenomena which would not be expected in the type of isomerism 

 suggested. The production of the diquinaldine and of the 

 benzerythrene derivatives in the case of Cain's isomerides and 

 of the hydrazide in the case of the 2 : 6'-dinitro-diphenic acid 

 seems to call for further explanation. 



Another case of unexplained isomerism is recorded by 

 Franzen and Helwert {Ber., 1 920, 53 [B], 3 1 9), who have obtained 

 a new form of i -chloro-4-nitronaphthalene in the preparation 

 of this compound from 4-nitro-a-naphthylamine through the 

 diazo-reaction. As, however, the second form was obtained in 

 a unique experiment, and the authors failed to repeat its pre- 

 paration, confirmation is necessary. This observation calls to 

 mind the existence of two isomeric sulphides of /S-naphthol 

 described by Crymble Ross and Smiles {Trans. Chem. Soc, 

 191 2, 101, 1 146) which still awaits a satisfactory explanation. 



Constitution of the Triphenylmethane Dyes. — Although the 

 problem of the constitution of the triphenylmethane dyes 

 attracted the attention of many famous chemists, little work 

 has been done on this subject lately, and the quinonoid struc- 

 ture has been very generally adopted. Meisenheimer and 

 Neresheimer {Ann., 192 1, 423, 105) have, however, attempted 

 to prepare optically active leuco-bases of the triphenylmethane 

 dyes. If Rosentiehl's formula for these dyes is correct optically 

 active leuco-bases on oxidation should give optically active 

 dyes, but if a quinonoid compound is formed the optical activity 

 should disappear. They tried to resolve compounds of the 



