CAPROIC ACID. 65 



Physiological Relations. 



Occurrence. Although this acid is so easily and so variously 

 obtained from animal substances, it has never yet been found pre- 

 formed in the animal organism ; and it is a striking fact that, so 

 far as we yet know, the acids of this group, whose amount of carbon 

 is divisible only by 2, and not by 4, are not found in the animal 

 organism. 



We shall consequently only have occasion to refer to these acids 

 in the following pages, inasmuch as they sometimes occur as 

 products of the artificial decomposition of animal substances. 



CAPROIC ACID. C 12 H H O 3 .HO. 



Properties. It is a somewhat thin liquid, with an odour resem- 

 bling sweat; its specific gravity at +26=0*922; it remains fluid 

 at 9, boils at 202, and dissolves somewhat difficultly in ether. 



Composition. According to its formula it consists of: 



Carbon 12 atoms .... 62-069 



Hydrogen 11 .... 9'483 



Oxygen 3 .... 20'689 



Water 1 .... 7'759 



100-000 



The atomic weight of the anhydrous acid =r 1337*5 ; its 

 saturating capacity = 7'476. According to the views of Kolbe, 

 this acid should hypothetically be regarded as amyloxalic acid 

 C 10 H n .C 2 H 3 .HO. 



Combinations. The caproates have the same taste and smell as 

 the acid itself; and are mostly soluble in water and crystallisable. 

 The baryta-salt crystallises in long silky needles, united in tufts, is 

 anhydrous, and unaffected by exposure to the atmosphere; the 

 silver-salt is not crystallisable, and is very difficult of solution. 



Preparation. Like butyric acid, this acid is not only formed 

 when butter is saponified or becomes rancid, but also when oleic 

 acid is decomposed by fuming nitric acid, and when albuminous 

 bodies are acted on by peroxide of manganese or bichromate of 

 potash and sulphuric acid. In the products of the decomposition 

 of saponified butter we find caproic acid mixed with butyric, 

 caprylic, and capric acids, which may be removed by the crystal- 

 lisation of their baryta-salts. On boiling the dried mass of the 

 baryta-salts with 5 or 6 parts of water, the butyrate and caproate 



