1872.] Dr. A. W. Hoftnami on Aromatic Monamines. 51 



of the dimethylated base, it appeared desirable to establish the nature of 

 the latter by additional experiments. For this purpose the tertiary 

 monamine was converted, by means of methyl iodide, into the quartary 

 compound, the characters of which could not be mistaken, its composition 

 being moreover established by analysis of the beautiful platinum salt, 

 2[C 6 H 3 (CH 3 )J (CH 3 ) 3 N CI] . Pt Cl 4 . 



In performing these experiments I was astonished to observe how 

 difficultly dimethylxylidine combined with methyl iodide. Digestion at 

 100° produced no effect, and only by heating the mixture for many hours 

 to a temperature of 150° combination took place, but even then only to a 

 very small extent. 



It was this indifference of dimethylxylidine towards methyl iodide 

 which enabled me to discover that small quantities of this compound are 

 always formed, together with the monomethylated xylidine, when tri- 

 methylated phenylammonium iodide is submitted to the action of heat. 

 On treating the liquid, chiefly consisting of the two dimethylated toluidines 

 and of monomethylated xylidine, with methyl iodide, these bases, as I 

 have pointed out, are converted into iodine compounds ; the small quan- 

 tity of dimethylxyhdine which as such exists in the liquid remains behind 

 with the excess of methylic iodide, from which it may easily be sepa- 

 rated by means of hydrochloric acid. 



The formation of dimethylated toluidines and of monomethylated xyli- 

 dine requires no special explanation ; it is due to intramolecular atomic 

 interchange. 



C 6 H 5 (CH 3 ) 3 NI=(C 6 H 4 . CH 3 )(CH 3 ) 2 N.HI. 



=[C 6 H 3 .(CH 3 )JCH 3 HN.HI. 



For the generation of dimethylxylidine it is necessary to supply a 

 methyl group from without. I have, however, already pointed out that, 

 along with the principal transformation, several secondary reactions are 

 taking place ; those I hope to examine more minutely by-and-by. Di- 

 methylxyhdine, which occurs in comparatively small quantity, obviously 

 belongs to such a secondary change. The complementary product is pro- 

 bably monomethyltoluidine, 



2[C e H 5 (CH 3 ) 3 NI]=(C 6 H 4 . CH 3 ) CH 3 HN.HI, 

 + [C„H 3 .(CH 3 )J(CH 3 ) 2 N.HI, 



which I have not, however, as yet been able to trace. 



Whilst engaged with these experiments, I have, for the sake of com- 

 parison, converted a specimen of xylidine obtained from aniline-oil of 

 high boiling-point into dimethylxylidine. The xylidine employed had a 

 constant boiling-point at 216°. The tertiary base procured from it was ob- 

 served to boil at 203°, i. e. 7° higher than the compound derived from tri- 

 methylated phenylammonium iodide ; from this last derivative it differed, 

 moreover, by combining much more readily with methyl iodide. The 



