ON ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 217 



Sur I'absorpiion de la lumiire par les indophenols By P. Bayrac and 



C. Camichel.^ 



The indophenols with tertiary nitrogen, prepared by one of the 

 authors, were studied, and it was found that when dissolved in the 

 same solvent, as, for instance, alcohol, they presented an analogous 

 spectrum in every case. They are characterised by a band in the red. 

 Lemoult studied a series of indophenols obtained by the oxidation of 

 mixtures of ^j- phenylenediamine and phenol or o-cresol, which have in 

 the joarrt-position the nitrogen atom which unites the two benzene nuclei. 

 The nitrogen in this case is primary and not tertiary. The substances 

 are said to have a band in the red which is shifted from the position 

 characteristic of indophenols containing tertiary nitrogen. The authors 

 state that there may be displacement of the band, but it has no definite 

 direction ; and the experiments of Lemoult do not show that it has. The 

 method of measuring adopted by Lemoult is to take the mean of the 

 micrometer readings between either edge of the band. It is remarked 

 that the extreme reading at the extremity of least refrangible rays is not 

 the end of the band, but merely the limit of visible rays, and that this is 

 variable according to the brilliancy of the spectrum. They give reasons 

 for this statement which are capable of verification, and also for the 

 explanation that there ap^jears to be a displacement, but the band really 

 terminates in the infra-red. 



Sur les spectres d'absorption des indophenols et des colorants du 

 triph^nyhne'thane. By C. Camichel and P. Bayrac. ^ 



The indophenols with the tertiary nitrogen are much more absorbent 

 than those with the primary nitrogen when the two are compared in 

 solutions containing molecular proportions ; but the fact is that as the 

 less refrangible end. of the band visible in the red lies in the infra-red 

 there can be no increased width visible in this direction, and the rays on 

 the other side being more freely transmitted it appears as if the band 

 had been shifted towards the more refrangible rays. This having been 

 demonstrated with the two kinds of indophenols, it was thought desirable 

 to study the triphenylmethane derivatives — malachite green, sulpho- 

 green J, hexamethylene violet crystals, and methyl green. The result 

 was just the same; only one extremity of the band of red rays lies within 

 the region of visibility. The conclusion is that the law of auxochromes 

 has not been demonstrated in the case of triphenylmethane dei'ivatives 

 nor of indophenols. The number of tertiary nitrogens in the molecule 

 is the factor which increases the absorbent power of the substance, just 

 as the substitution of (0113)3 for H3 in indophenols, or vice versa, renders 

 the substance more or less powerfully absorbent. The authors state that 

 they have studied the influence of concentration upon alcoholic solutions 

 of indophenols and on aqueous solutions of those colouring matters derived 

 from triphenylmethane. They have found that the coefficient of absorp- 

 tion is proportional to the concentration of the solution . 



Note. — The nature of the indophenols is indicated by the following 

 formulae and reactions, the notes being taken from Bernthsen's ' Organic 

 Chemistry ' and Witt's original papers.^ 



' Comptes Eendus, vol. cxxxii. 1901, p. 338. * lUd., cxxxii. 1901, p. 485. 

 ^ Berichte, 16, 2843, and 18, 2912. 



