LECTURE XIII.] HISTORY OF CHEMISTRY. 263 



Kolbe is also acquainted with a dimethyl-acetic acid, which 

 he calls isobutyric acid, since it is different, according to him, 

 from ordinary butyric acid : 



/ C. 2 H 3 \ 

 C,-C,H 3 



V H 



C,.H-(C.,O.,)O,HO C,- C,H, C,O.,,O,HO 



V ( "H/ 



Butyric acid. Isobutyric acid. 



Kolbe assumes three isomeric substances having the formula 

 of valerianic acid : trimethyl-acetic acid, methyl-ethyl-acetic 

 acid, and propyl-acetic acid. Isomeric derivatives correspond 

 to these compounds, such, for example, as oxyacids, amongst 

 which Kolbe classes Stadeler's acetonic acid. 47 



These views were completely confirmed, and Kolbe's clever 

 prediction thereby achieved a great triumph. FriedeFs acetone 

 alcohol was the first compound representative of this class of 

 substances that was prepared, and it, therefore, is of great 

 importance. As the constitution of acetone had been settled 

 by Freund's synthesis, there could scarcely be any doubt as to 

 the formula of the new propyl alcohol ; and this formula was 

 employed by Erlenmeyer 48 (after he had found that the alcohol 

 was identical with the one prepared from glycerine 49 ) in 

 explaining the constitution of the triatomic alcohol. 



The discovery of the "hydrates" by Wurtz 50 followed 

 immediately after the discovery of isopropyl alcohol. Wurtz 

 obtained these substances by treating the hydrocarbons of the 

 ethylene series with hydriodic acid and silver oxide ; and he 

 studied their properties particularly in the case of amylene 

 hydrate, where he was able to recognise its difference from amyl 

 alcohol. At first he looked upon this substance as a compound 

 of the hydr^arbon with water, and represented it by the formula 

 C 5 H ]0 , H.,O, a view which appeared to be warranted by its 

 ready decomposition into these substances. At a later period 

 he belte^l^mat the divergences from the normal alcohols 

 could be explained on the assumption that the union of the 



47 Annalen. in, 320. * Ibid. 139, ill. 49 Zeitschrift ftir Chemie. 7, 

 642. 50 Comptes Rendus. 55, 370 ; 56, 715, 793 5 57> 479- 



