70 THE BUTYRIC ACID GROUP. 



it was first discovered by Redtenbacher.* Gerhard tf has obtained 

 this acid by oxidising oil of rue, C. 20 H 19 O 3 , with nitric acid. 



Tests. By the crystallisation of its baryta-salt we must pre- 

 pare this acid so that we can make an elementary analysis and 

 determine its atomic weight. 



Physiological Relations. 



The remarks already made regarding the physiological relations 

 of oenanthylic acid are equally applicable here. 



CAPBIC ACID. C 20 H 19 O 3 .HO. 



Chemical Relations. 



Properties. Little is yet known regarding this acid in a state 

 of purity, for what was formerly regarded as capric acid was a mix- 

 ture of capric and caprylic acids. It constitutes a soft, greasy 

 mass which fuses at + 30, and evolves a faint goat-like odour, is 

 somewhat soluble in hot water, but separates on cooling in glis- 

 tening crystalline particles ; its boiling point is higher than that of 

 any of the other acids of this group, but is considerably below 

 300. 



Composition. According to the above formula it consists of : 



Carbon 20 atoms .... 69'7f>7 



Hydrogen .... 19 .... 11*046 



Oxygen 3 .... 13-954 



Water 1 .... 5*233 



100-000 



The atomic weight of the hypothetical dry acid= 2037*5; its 

 saturating capacity^ 4-909 ; its rational formula=:C 18 H 19 .C 2 O 3 .HO. 



Combinations. The salts of this acid are more insoluble than 

 those of the other acids of this group. The baryta-salt crystallises 

 in delicate, glistening needles ; it is unaffected by exposure to the 

 atmosphere, and contains no water. 



Oil of rue, C. 20 H 19 O, the ethereal oil of Ruta graveolens, may be 

 regarded as anhydrous aldehyde of capric acid ; in point of fact it 

 is converted into capric acid by the action of nitric acid ; but by 

 more prolonged action, into pelargonic acid. 



* Ann. d. Ch. u. Pharm. Bd. 59, S. 41-57, and Bd. 57, S. 170-174. 

 t Aua.de Ch. et dc Phys. T. 24, pp. 112-116. 



