236 HISTORY OF CHEMISTRY. [LECTURE XII. 



radical, a ketone is formed, and when it is replaced by hydrogen 

 an aldehyde is formed : 



?TT JGoO, Aldehyde ; &5 8 JC 8 O 2 Acetone. 



^2 "3-' \-"2"-$J 



By the replacement of three atoms of oxygen by three of 

 hydrogen, or by two of hydrogen and a radical, the alcohols 

 are obtained : 



HO H 3 C 2 , O Methyl alcohol. 



HO ~ 54a, O Ethyl alcohol, etc. 

 U 2 tigj 



If this mode of deriving substances is more minutely 

 examined, we recognise that Kolbe's procedure is not altogether 

 justified. By the replacement of an atom of oxygen in carbonic 

 acid by hydrogen, HC. 2 O 3 is obtained, and not formic acid. 

 Kolbe simply adopts from the dualists, the error of sometimes 

 adding HO to the formula, and sometimes omitting it. It is 

 true that he states a reason for his doing so, inasmuch as the 

 basicity of a compound (and therefore also the number of 

 HO groups) is determined, according to him, by the number 

 of oxygen atoms outside the radical. Thus nitric acid is mono- 

 basic, since it is (NO 4 )"O; sulphuric acid is dibasic because it 

 contains two oxygen atoms outside the radical (S.,O 4 ) O 2 ; and 

 phosphoric acid is tribasic (PO. 2 )O 3 . 



Since, in accordance with this mode of regarding the 

 matter, every atom of oxygen outside the radical carries -with 

 it one OH group, when Kolbe speaks of the replacement of 

 such an atom of oxygen, this means that O + OH = O.,H is 

 substituted ; and, taken in this sense, the view can be sustained 

 in a strictly logical manner. It is necessary, however, to start 

 from the hypothetical hydrated carbonic acid 2 HO, (C 2 O 2 ) O. 2 . 



By the replacement of 



O H by H we get HO,H(C,O,)O Formic acid, 



O 2 H CoH 8 HO,(C 2 H 3 )~(C 2 O 2 )O Acetic 



2O 2 H H 2 HJC 2 O 2 Methyl aldehyde, 



20.,H (C.,H 8 ).,,, &2 8 )c.,0o Acetone, 



