LECTURE XI.] HISTORY OF CHEMISTRY. 203 



notions introduced by Dumas at the same time, and of the rule 

 of Gerhardt mentioned above. This does not apply to the 

 opponents of these views, as I shall prove by means of an 

 example. Kolbe and Frankland prepared methyl (ethan), in 

 1848, by treating ethyl cyanide with potassium, and they 

 assigned to it the formula C 2 Hj [C = 6]. 19 They subjected 

 this substance to the action of chlorine in order to convert it 

 eventually into methyl chloride. Instead of the latter they 

 obtained a compound having the same composition as ethyl 

 chloride, but which instead of becoming liquid at 12, remained 

 gaseous at - 18. This they regarded as isomeric with ethyl 



TT 



chloride, and they formulated it C 2 H 3 . C 2 Q, that is, as a 



coupled compound of methyl with another atom of methyl in 

 which one atom of hydrogen is replaced by chlorine. With 

 Kolbe and Frankland, therefore, the existence of the first sub- 

 stitution product C 4 H 5 C1 was no reason for assigning the for- 

 mula C 4 H 6 to the original hydrocarbon. Laurent was of a 

 different opinion. Prior to the isolation of the alcohol radicals, 

 he had proposed for them, in case they should be discovered, the 

 formulae now adopted. 20 Afterwards, when Kolbe had discovered 

 a general method for the preparation of the alcohol radicals by 

 the electrolysis of salts of the fatty acids, 21 Laurent and Ger- 

 hardt return to this view in a detailed manner and designate 

 them as homologues of marsh gas. 22 A. W. Hofmann allies 

 himself with them in so far that he leaves the possibility of 

 isomerism between the alcohol radicals and the homologues of 

 marsh gas an open question. 23 It is otherwise with Frankland, 

 who defends the formuke corresponding to two volumes for 

 the alcohol radicals, as opposed to those corresponding to four 

 volumes, and formulates methyl, C 2 H 3 , and ethyl hydride, C 4 H 6 , 

 afterwards just as he had done before. 24 



The conception of the chemical molecule was more readily 

 appreciable by Laurent, Gerhardt, and Hofmann. They en- 



19 Annalen. 65, 279. 20 Ann. Chim. [3] 18, 283. 21 Annalen. 69, 257. 

 22 Comptes rendus mensuels des travaux chiniiques. 1850. 2 Annalen. 

 77, 161. 24 Ibid. 77, 221. 



