Drs. Muspratt and Hofmann on Toluidine. 187 



not possibly be distinguished one from the other by smell. 

 Toluidine has no action upon curcuma paper, but it colours 

 green the pigment of dahlias. Reddened litmus paper is 

 faintly blued. Toluidine is heavier than water. It evapo- 

 rates at all temperatures, and vi'hen a glass rod moistened with 

 hydrochloric acid is held over it white fumes are perceptible ; 

 this also takes place with nitric acid, but in a less degree. 

 When pressed with the hand between paper it leaves a slight 

 stain, which is however very fugitive. The fusing-point of 

 this base lies at 40° C, the boiling-point exactly at 198° C. 



Some years ago Professor Kopp * drew attention to the re- 

 markable relation subsisting between the boiling-points of 

 bodies whose composition differs in a constant number of equi- 

 valents of the same elements. He found, for instance, that 

 the difference in the boiling-points of two compounds which 

 differ by two equivalents of carbon and two equivalents of 

 hydrogen (Cg Ha) is invariably 19° C. Kopp showed this at 

 first by comparing the boiling-points of a vast number of 

 ethyle and methyle compounds, and then the numerous hy- 

 drated acids differing in Cg Hg. Since that time this concur- 

 rence between a series of newly^discovered aethers and acids 

 has been perfectly confirmed, but it seems to take place only 

 in bodies of an analogous character, as remarked by Kopp 

 and subsequently by Fehling f. 



We possess in benzole and toluole and their derivatives also 

 two series of analogous bodies, whose composition is distin- 

 guished by the constant difference C^ Hg. It was of interest 

 to compare the boiling-points of these bodies in the sense re- 

 ferred to. 



Boiling-point. Difference. 



Benzole 86° C— Mitscherlich ... \ nao 



Toluole, 108°.— Deville J- ^^ 



Nitrobenzide 213°. — Mitscherlich. . \ ^^o 

 Nitrotoluide 225°.— Deville .... J 

 Aniline 182°.-.A. W. Hofmann • • 1 |^o 

 Toluidine 198°.— Muspratt & Hofmann/ 

 This comparison shows undoubtedly that Kopp's rule holds 

 good with regard to the above-cited bodies. 



The differences evidently arise from mistakes in observa- 

 tion. As for the boiling-points of nitrobenzide and nitroto- 

 luide, the somewhat considerable variation can by nowise sur- 

 prise, knowing as we do with what readiness bodies of this 

 nature undergo decomposition when submitted to distillation. 



♦ Ann. der Chem. und Pharm.,\o\. xlii. p. 79. fPhil. Mae. S. 3. vol. xx, 

 p. 187.] 



t Ibid., vol. liii. p. 410. 



