( 348 ) 



salts. This form of deoomposi tioM is therefore, quite distinct from (he 

 photochemical splitting. The question is what (he electrolysis of the 

 acid might be able to teach us ? 



§ 8. In the study of the photochemical decomposition of the ferric 

 salt of trichloroacetic acid we found C^ Clg and CO^^ as the main 

 products. This splitting of the acid is apparently quite analogous to 

 that observed in the electrolysis of the carboxylic acids and their 

 salts '). KoLBF, found that the acetates, in favourable circumstances, 

 give mainly C\ H^ and CO.^ ; Kaufler and Herzog, however, get 

 with monochloroacetic acid different results, namely, always a 

 liberation of CI and formation of formaldehyde ; Herzog (Diss.), 

 however, also founii in addition metliylene-chloride (in the case of 

 bromoacetic acid, methylene-bromide and with iodoacetic acid, me- 

 thylene-iodide and also iodine) ; Crum Brown and Walker obtained 

 from ethylpotassium-malonate the dietliyl-ester of succinic acid ; also 

 from succinic acid, adipic acid ; from adipic acid, sebacic acid and 

 from the latter suberic acid. Kaufler and Herzog succeeded, moreover, 

 in proving, by means of an anode charged with iodine, that the 

 formation of C^ H^ from acetic acid does not take place according 

 to the mechanism suggested by Kékulé and Bourgeoin (Ann. d. 

 Chem. 131 79. (1864; and Ann. de chim. phys. (4), 14. 157 (1868) 

 neither in the manner represented by Schall (Z. fur Electrochem. 

 3. 86. (1896)), but simply according to: 



2CH3.CÖ.O + 2©^2CH3.CO.O-2CO, + 2CH3 = 2CO, + C,H,. 



The intermediary formation of the 6W3 -groups was proved by the 

 generation of CH^ J, which was fixed as phenyldimethylammonium 

 iodide and determined as such. 



Hence, if, in the electrolysis of trichloroacetic acid, C^ Cl^ could 

 indeed be obtained besides CO.^ , the photochemical splitting of the 

 iron salt would be quite analogous to an electrolytic process. 



. This fact is of great theoretical significance. With our veiy imper- 

 fect knowledge of the mechanism of the photochemical reactions several 

 theories as to its nature have originated wdiich each have their pro 

 and contra, according to the particular cases in which they are applied. 



^) KoLBE, Lieb. Ann. 69. 257 (1849); Jahn. Wied. Ann. 37. 408.(1880); Grum 

 Brown and Walker, Lieb. Ann. 261. 107. (1890): Kaufler and Herzog, Bed. Ber. 

 42. 3858. (1909); Feist, Berl. Ber. 33. 2094. (1900; von Miller and Hofer, Berl. 

 Ber. 28. 2427 (1895); Elbs and Kratz, Journ. f. prakt. Chemie, N. F. 55. 502. 

 (1897); Elbs. ibid. (2). 47. 104; G. Herzog, Inaug. Diss. Zurich, 1909; Troeger 

 and Ewers, J. f. prakt. Ghem. (2). 58. 127. (1898). 



