649 



snlpbiiric acid. The absorption bands disappear wholly from the spec- 

 tiiini, and only a modest continuous absorption in the nltraviolel remains 

 (comj)are curves 14 and 15). For a concentration of 0.0002 gram- 

 molecules per litre and an absorbing layer of 100 m.m. the beginning 



of the absorption is repelled by the sulphuric acid from - 2150 to 



3400. This decoloration of picrylmethylamide by sulphuric acid is 

 just the reverse of the coloration of the nitramine with alkali. In 

 the tirst case the nitro groups of the nucleus are deprived of the 

 opportunity to combine with a basic grouji, in the latter case this 

 opportunity is on the contrary given. 



The reaction wiili alkalies seems to be the same for the acylderi- 



vatives now investigated as for tlie picrylalkylnitramines, the only 



difference being that they want a little more alkali for the red 



coloration. F'ormerly we found {llec. tniv. chim. 1913, 32, 332), 



that a sohition of picrylmethylnitramine containing an excess of 



1 

 alkali gives two bands at — 1975 and 2350. At nearly the same 



places two bands are shown by the alkaline solutions of the acetyl 

 derivative (curve 6) and the urethanes (9 and 11), though one of 

 the bands is only represented by a flat part of the absorption curve. 



The anomalous curve given by the nitrosamine with alkali (4) 

 will be discussed separately. 



Picrylphenylmethylaraide, the last derivative of picrylmethylamide 

 we examined, exists in two fornis of the same dark red colour but 

 of different mebing points, 108 and 129". Hantzsch {Bei\ 1910, 93, 

 1651) calls the two forms homochromo isomerides, whilst Biilmann 

 {Ber. 1911, 44, 827) regai-ds them as polymorphous forms. 



As Hantzsch has already observed, the spectra of the two forms 

 are completely equal (curve 12). It was now found, that the « and ^ 

 forms in presence of alkalies also behave in the same way (curve 13), 

 so that the two forms when dissolved seem to be wholly identical. 

 The broad absorption band of the amide at 2350 becomes by addition 

 of alkali a little deeper and is' somewhat displaced to larger wave- 

 lengths. At the same time it undergoes a division into a flat part at 

 2070 and a feeble band at 2400. This agrees with the behaviour 

 of the other compounds with bases. 



Finally we have examined the coloration of 1,3,5-trinitrobenzene 

 with alkali, since liere only the nitrogroups of the nucleus can act 

 with the base. 



Whilst trinitrobenzene only absorbs continuously (curve 1), addition 



43- 



