1865.] of the Series C n Il 2n+2 . 165 



In their Report to the Paris Academy upon these hydrocarbons, Laurent 

 and Gerhard t proposed that their formulae should be doubled, because 

 these bodies, if represented by the smaller formulae, would in the gaseous 

 state occupy two volumes instead of the four volumes in which the mole- 

 cule of all other organic compounds was found to occur ; and they con- 

 sidered these bodies as homologues of marsh-gas. Hofmann afterwards 

 expressed himself in favour of the larger formulae on the same grounds, and 

 also because, if Frankland's and Kolbe's formulae are accepted, the increase 

 in the boiling-point produced by an increase of CH 2 in the hydrocarbon 

 would be double that which has been observed as the difference in the 

 boiling-points of other homologous series. 



Besides these radicals, Frankland discovered another series of hydro- 

 carbons, which, according to the mode of their formation, he regarded as 

 the hydrides of the radicals, and as the true homologues of marsh-gas, and 

 which, according to a view first propounded by Brodie, are considered to 

 stand in a similar relation to the radical hydrocarbons as alcohol stands to 

 ether, viz. 



Hydride of ethyl. Ethyl. 



C 2 H S 1 C 2 HA 



HJ C 2 H 5 | 



Alcohol. Ether. 



C2 5 5 JO. r 2 TT 5 ) 



H/ C 2 HJ 



Brodie anticipated the existence of mixed radicals, as ethyl-amyl, Q 2 5 [ , 



CHI 



bearing the same relation to the simple radical, n 2 v( > as Williamson's 



mixed ether, & JJ 5 i O, to common ether, n 2 ! O. The researches of 



U 5 H u J t-'a 0-, J 



"Wurtz have fully realized this anticipation. Wurtz discovered a new 

 method of preparing the alcohol radicals by the action of sodium upon the 

 iodides ; and according to this method he not only obtained the hydro- 

 carbons discovered by Kolbe and Frankland, but, by employing two dif- 

 ferent iodides, he prepared a number of mixed radicals, which he also 

 obtained by the electrolysis of a mixture of two fatty acids. 



The results of Wurtz' s investigation have always been regarded as a 

 convincing proof of the correctness of Brodie's view, and it is now generally 

 believed that two series of hydrocarbons of the formula C n H 2)l+3 exist, the 

 hydrides and the radicals, the molecule of the latter containing two atoms 

 of the real radicals which are supposed to exist in the alcohols. 



A very remarkable resemblance is observed in the general physical pro- 

 perties of the two series, the members of which are gases or liquids so in- 

 different as to resist even the action of concentrated sulphuric or nitric 

 acids. This resemblance is so great that Greville Williams was led to the 

 opinion that the indifferent hydrocarbons which he discovered in the oils 

 obtained in the destructive distillation of Boghead coal belonged to the 



