66 THE BUTYRIC ACID GROUP. 



are taken up, while the salts of caprylic and capric acid remain 

 undissolved. The caproate of baryta is the first to crystallise from 

 the solution, and the acid may easily be isolated from the salt. 



Tests. The caproate of baryta not only crystallises sooner than 

 the butyrate, but also sooner than the valerian ate, if this should 

 happen to be present; caproate of baryta forms small clusters, 

 consisting of microscopic prisms, while the valerianate, as we 

 have already mentioned, appears in minute plates like cholesterin. 

 This separation of caproic acid from its allied acids, is more easily 

 explained theoretically than effected practically. There are no 

 special means of determining the presence of caproic acid, except 

 by an elementary analysis, and the determination of the atomic 

 weight. 



Physiological Relations. 



Occurrence. The remarks which we made regarding the occur- 

 rence of butyric acid in the animal organism, apply equally to 

 caproic acid. From its peculiar sweat-like odour, it is not impro- 

 bable that it exists in sweat; but of this we have as yet no proof. No 

 one, so far as I know, has yet sought for it in the urine or in the 

 contents of the stomach. In our observations on butyric acid we 

 alluded to the fatty matters contained in the milk, and probably also 

 in the blood, which, on saponification, yield this acid. 



CENANTHYLIC AdD. C 14 H 13 O 3 .HO. 



Chemical Relations. 



Properties. It is a colourless oily liquid, of a faint aromatic 

 odour and taste; it boils at about 215, may be distilled with only 

 partial decomposition, dissolves slightly in water, and when inflamed 

 burns with a clear but smoky flame. 



Composition. According to the above formula it consists of : 



Carbon 14 atoms .... 64-615 



Hydrogen 13 .... lO'OOO 



Oxygen 3 .... 18'462 



Water I 6'923 



100-000 



The atomic weight of the hypothetical anhydrous acidrr 

 1512-5, and its saturating capacity =6*611. Its rational formula 

 =C 12 H 13 .C 2 3 .HO. 



