LECTURE XII.] HISTORY OF CHEMISTRY. 229 



of acetic acid by replacing the methyl by ethyl, propyl, amyl, 

 etc., while in benzoic acid the radical phenyl occupies the place 

 of the methyl. In general, Kolbe employs the so-called homo- 

 logous and isologous radicals as equivalent to one another, just 

 as Gerhardt had done. 



The radical ethyl is assumed in alcohol, which Kolbe 

 writes (C 4 H 5 )O, HO, as Liebig also did, only with different 

 atomic weights ; on oxidation it splits into C. 7 H 3 and C.,H.,, 

 and the latter is then converted further into C 2 O . This 

 explanation is complicated in comparison with the one given 

 by Williamson, but still it afterwards led to important con- 

 clusions (see p. 237). 



Kolbe formulated Leblanc's monochloracetic acid, 38 and 

 Dumas' trichloracetic acid 



2 , 3 and HO(QC1 3 )C>,O 3 . 



The formulae become much more complicated in the case of 

 the products obtained by the action of sulphuric acid upon 

 organic acids, where the mode of writing them approximates 

 to that proposed by Dumas andPiria for the "acides conjuges." 39 

 Sulphacetic acid, for example, becomes 



c " 



c,-< so, Co, o 





Kolbe is still undecided at this time as to whether he should 

 admit the existence of dibasic acids, and he, therefore, retains 

 the old formulae. Accordingly, oxalic acid is HO, C,O 3 , and 

 succinic acid is HO, (CoH. 2 )C,O 3 . 



It is also worthy of mention that Kolbe assumes radicals 

 containing oxygen in anisic and in salicylic acids, and that he. 

 therefore, no longer agrees with Berzelius upon this point. 



In addition to the conjugated metallic radicals and carbon 

 radicals, Kolbe also recognises radicals containing sulphur, 

 and thus the analogy, already noticed, between the ordinary 



38 Ann. Chim. [3] 10, 212. 39 Annalen. 44, 66. 



