60 Colouring-matters from Aromatic Azodiamines. [Dec. 5, 



brief notice published by Mene *, saf rauiue is obtained by treating aniline 

 successively with nitrous and arsenic acids ; this process very closely 

 agrees with the method by which M. Girard, as he informs us, has pre- 

 pared the specimen transmitted to us. We have, moreover, to thank M. 

 Girard for pointing out that aniline of a very high boiling-point is 

 especially adapted to the preparation of safranine. 



After some practice we have been able, by working according to these 

 indications, to obtain safranine with all the properties of the commercial 

 product. The yield, however, was always very small, an exceedingly 

 large quantity of but little attractive by-products being invariably formed. 

 Somewhat more satisfactory results were obtained when chromic instead 

 of arsenic acid was used as oxidizing agent. Our experiments, though 

 unsuccessful as regards the discovery of a good method for preparing 

 safranine, nevertheless appear to supply some welcome indications 

 as to the real source of the colouring-matter. Neither from pure 

 aniline nor from solid toluidine have we been able to obtain safra- 

 nine by the above-mentioned process; nor did a mixture of pure 

 aniline and solid toluidine yield a better result. We have, 

 however, invariably obtained safranine when liquid toluidine, boiling 

 at 198°, was used for the experiment. This colouring-matter thus appears 

 to become a pure derivative of toluidine, and the formula 



C 21 H 20 N 4 , 



to which analysis had led, is corroborated, as far, at all events, as the 

 number of carbon-atoms in the molecule of safranine is concerned, in a 

 most satisfactory manner by the formation of this body. In this forma- 

 tion, as in that of rosaniline and of the allied tinctorial ammonias, 3 

 mols. of monamine associate with a complex molecule, 3 atoms of hydrogen 

 in which are displaced by one of nitrogen, 4 atoms of hydrogen being, 

 moreover, removed by oxidation. 



3C 7 H 9 N+HNO,=C a H 24 N 4 +2H 2 0. 

 C 21 H 24 N 4 +20=C 21 H 20 N 4 +2H 2 0. 



A glance at the safranine formula with its four nitrogen-atoms recalls 

 the composition which Mr. Perkin ascribes to mauveine. 



Safranine c 2 i H 20 ]Sr 4 . 



Mauveine C 27 H M N 4 . 



The idea suggests itself that mauveine might be phenyl safranine, 



C 27 H 24 N 4 =C 21 H 19 (C 6 H 5 )N 4 . " 



In fact saf rauiue salts yield a violet colouring-matter when boiled for 

 some time with aniline ; again, saf rauiue and mauveine exhibit nearly the 

 same changes of colour under the influence of concentrated acids. 



* Mene, from the Revue Hebd. Chim. Scient. Indust. Feb. 29, 1872, in Chemical 

 News, vol. xxt. p. 215. 



