212 PROFESSOR A. CRUM BROWN AND DR JAMES WALKER ON THE 



proceeds chiefly according to equation I. With other acids, however, the result is 

 different. Potassium valerianate, for example, yields on electrolysis considerable quantities 

 of valerianate of butyl * formed according to equation II. ; thus 



2C 4 H 9 -COO = C 4 H 9 -COOC 4 H 9 +C0 2 . 



Another and particularly interesting case is that of the electrolysis of a formiate. If the 

 reaction took place in the sense of equation I 



2HCOO = H 2 +2C0 2 , 



we should have the somewhat surprising circumstance of hydrogen being given off at 

 both poles. As a matter of fact, no hydrogen is formed at the anode, but the reaction 

 which occurs is as follows : — 



2HCOO = H-COOH + C0 2 ; 



formic acid is regenerated and carbonic acid alone is evolved.t This process has been 

 looked upon as one of oxidation, but it is clearly a case of the occurrence of the mode of 

 decomposition symbolised by equation II. 



There is still another way in which two anion molecules may react together. It 

 occurs chiefly with the higher fatty acids, and results in the formation of unsaturated 

 bodies. For instance, a propionate gives as chief product at the anode, ethylen,| according 

 to the equation 



III. 2C 2 H 5 COO = C 2 H 4 +C0 2 + C 2 H 5 COOH . 



It evidently depends on the relative stability of the various possible products of 

 decomposition which of these three reactions will prevail. The most interesting case, 

 however, is that in which two alkyl residues from different molecules unite to form a 

 hydrocarbon (equation I.) ; for this gives us the means of effecting the synthesis of long 

 carbon chains. 



Till now only a few hydrocarbons have been thus synthetically prepared. The method, 

 however, is by no means confined to such substances, but is capable of considerable 

 extension ; and in the present paper will be found its development in one particular 

 direction. 



It is a well-known fact that the specific function of any class of substances in organic 

 chemistry is determined by the presence within them of a definite group of atoms. 

 Acids are thus characterised by the carboxyl group, primary alcohols by the radical 

 CH 2 OH.§ Now it often happens that one and the same substance contains two 

 characteristic radicals ; the substance then belongs formally to two families, and has in 

 general the properties of both. A short time ago one of us expressed in the Proceedings 



* Kolbe, loc. cit., 164. 



t Jahn, Wiedemann's Annalen, xxxvii., 408, 1889. 



\ Jahn, loc. cit., p. 430 ; compare also Kolbe, loc. cit., p. 168. 



§ Compare Crum Brown, Trans. Roy. Soc. Edin., xxiv. 331, 1866. 



