1855.] Constitution of the Hydro-carbons. 65 



can be readily detected ; but with regard to H CI and Et CI, the 

 CI can be detected in the former only. 



All the facts connected with the mutual relations of 



C* H* — ethylene, or olefiant gas 

 C*H*0 -aldehyd 

 C*H*0*— acetic acid 

 C* H" — hydro-ethylene 

 C* H* CI — muriatic ether 

 C* H« O —alcohol, 



especially since the recent researches of Berthelot, show the superi- 

 ority of Dumas' ethylene to Liebig's ethyl theory, both as regards 

 its more complete accordance with experiment, and its greater 

 generality. The probabilities in favour of the pre-existence of C* H* 

 and its derivatives, as constituent groups, are much greater than are 

 those in favour of the pre-existence of C* H*. Thus, with regard to 

 ethylene, hydro-ethylene, muriatic ether, and their chlorine deriva- 

 tives, we ought to have the following series, convertible into one 

 another through certain members : — 



Of these four series, three are undoubtedly, and the fourth most 

 probably, known to us. They illustrate rationally the nature of the 

 isomerism. In the three latter series, we have every reason to 

 believe, that, with regard to the carbon, two of the hydrogen or 

 chlorine atoms stand in a different relation to the other four ; but 

 in the first series, we have not a single fact tending to show, that one 

 of the hydrogen atoms stands in a different relation to the other 

 three ; not one fact to countenance the representation of olefiant-gas 

 by C* H«'H, hydruret of acetyl. 



In the next best known hydro-carbon, namely, benzine, there is 

 no more reason for believing in the existence of the monobasic 

 radical phenyl C* H', than there is for believing in the bibasic 

 and tribasic radicals C H* and C* H^, respectively, as seen in the 

 following table :— (X = NO* Ad = NH') 



