1872.] Dr. A. W. Hofmann on Aromatic Monamines. 49 



at 192°. The boiling-point was repeatedly determined, since it had been 

 erroneously stated by M. Lauth* to be 202°. The nature of the com- 

 pound was ascertained by the analysis of the beautiful platinum salt 

 2[C 6 H 3 (CH 3 ) 2 N.HCl].PtCl 1 , 



crystallizing in well-formed tables of considerable solubility. 



In the early experiments trimethylated phenylammonium iodide was 

 employed in the pure state, such as is obtained by crystallization ; sub- 

 sequently, however, it was found to be quite sufficient if 1 mol. of di- 

 methylaniline was mixed with 1 mol. of methyl iodide, and the compound 

 thus produced at once submitted to the action of heat. 



The quartary iodide may be exposed to a temperature of 200° for a 

 considerable time without undergoing any alteration ; but when heated 

 for a day to from 220° to 230°, the salt is changed, the whole crystalline 

 compound being transformed into an amber-yellow viscid mass, exhibit- 

 ing no longer a trace of crystalline structure. If the temperature be 

 then raised to the melting-point of lead (335°), a further change is mani- 

 fested by the amorphous resinous substance having solidified again to a 

 hard mass of large radiated, generally rather coloured crystals. On 

 opening the digestion-tubes, appreciable quantities of uninflammable gas 

 are evolved. 



The products formed at moderate and extreme temperatures essen- 

 tially differ from one another. This is seen at once when the iod- 

 hydrates produced in both casos are decomposed by alkali, and the bases 

 thus liberated are submitted to distillation in a current of steam. The 

 volatility of these bases shows the absence of quartary compounds ; but 

 whilst the monamines formed at moderate temperatures unite with acids 

 to extremely soluble salts, which are scarcely to be crystallized, those 

 which are produced at high temperatures are found to solidify to rather 

 difficultly soluble, readily crj^stallizable salts with acids. The former 

 bases exhibit the characters of tertiary and secondary, the latter ones those 

 of primary monamines. Under these circumstances, it appeared desirable 

 separately to examine the products formed in different conditions of 

 temperature. 



Examination of the Monamines formed at moderately High Temperatures. 



On submitting the iodhydrates formed at 220°-230° to distillation with 

 alkali, a basic oil is obtained which, when rectified after drying over 

 hydrate of potassium, boils between 200° and 280°. By repeated distilla- 

 tion the boiling-point is considerably lowered, small quantities of sub- 

 stances boiling beyond the range of the thermometer being separated. 

 Finally, by far the greater portion of the bases is found to pass between 

 186° and 220°. This liquid consists of two varieties of dimethyltolui- 



* Lauth, Bull. Soc. Chim. [2] vol.vii. p. 448. 



e2 



