292 On the Limited Oxidation of Ethyl-crotonic Acid. 



then, whilst still hot, placed under the receiver of the air-pump. 

 Of course this caused the contents of the flask to boil, and 

 thereby effectually expelled any carbonic acid that might be dis- 

 solved in the liquid. The strength of the standard chromic so- 

 lution had previously been ascertained by causing it to act on 

 excess of oxalic acid. The carbonic acid so liberated was dried, 

 absorbed by potash, and weighed. Two equivalents of carbonic 

 acid correspond to one of available oxygen. 



The chromic acid which had not been reduced by the ethyl- 

 crotonic acid was now estimated in the same way, and the car- 

 bonic acid so obtained deducted from the amount which the 

 known quantity of chromic solution would have liberated had no 

 portion of it been reduced. From the difference it is easy to 

 calculate how much oxygen the acid had consumed. 



The details of the operation are as follows : — 



Strength of chromic solution. 100 grms. of the solution libe- 

 rated 7*5182 grms. of carbonic acid from oxalic acid. 



Amount of chromic solution employed 51*02 grms. 



Ethyl-crotonic acid employed '4316 grm. 



Carbonic acid obtainable from unaltered chromic") QQQ k Q 

 solution J 



Carbonic acid obtained after digestion . . . 1*4496 



Difference, due to oxygen consumed .... 2*3862 



Two equivalents of carbonic acid correspond to one of oxygen. 

 Therefore 2CO' 2 = 88 : = 16 : : 2*3862 : at, 



x =-433854. 



Dividing this by the substance taken, we learn the percentage 

 of oxygen consumed, viz. . . . . . . 100*47 



Theory for seven equivalents . . 98*24 



Theory for eleven equivalents . . 154*38 



Therefore equation (1) is evidently correct. 



The above work was the first step in a proposed investigation, 

 by oxidation, of the acids of the acrylic series. It was intended 

 to collect these acids and treat them in a similar manner; but 

 the difficulty of obtaining any of these acids, excepting those 

 which could be formed synthetically from the corresponding- 

 secondary lactic acids, proved so great that the investigation was 

 temporarily abandoned. Should opportunity offer we intend to 

 resume it. 



Laboratoiy, London Institution. 



