PELARGONIC ACID. 69 



rate and caproate, and an undissolved portion, containing the 

 caprylate and caprate of baryta. If now the undissolved portion 

 be dissolved in boiling water and filtered while still hot, most of 

 the caprate separates while the caprylate remains in solution. In 

 order to effect a perfect purification, the baryta-salt must be several 

 times recrystallised before we separate the acid from it. 



Tests. We must separate the caprylic acid from the other acids 

 in the manner just described, and then determine the atomic 

 weight. 



Physiological Relations. 



Occurrence. All that has been remarked regarding the physio- 

 logical relations of butyric and caproic acids applies equally to 

 caprylic acid. 



PELARGONIC ACID. C ls H 1( ,Oo.HO. 



lo 17 O 



Chemical Relations. 



Properties. It is an oily, colourless fluid which at a lower tem- 

 perature than + 10 becomes solid, but liquefies at and above 

 that temperature ; it has a faint odour resembling that of butyric 

 acid, is almost insoluble in water, but communicates to it an acid 

 reaction, and boils at about 232. 



Composition. In accordance with the above formula it con- 

 sists of: 



Carbon 18 atoms .... 68-350 



Hydrogen 17 .... 10'760 



Oxygen 3 .... 15'190 



Water 1 .... 5'700 



100-000 



The atomic weight of the anhydrous acid = 1862*5 ; its satu- 

 rating capacity = 5 -369; its rational formulae C 16 H 17 .C 2 O3. HO. 



Combinations. The baryta-salt of this acid crystallises like the 

 valerianate and cenanthylate of baryta in glistening scales ; it con- 

 tains no water of crystallisation, is unaffected by the atmosphere, 

 and is less soluble than the osnanthylate and caprylate of baryta, 

 but rather more soluble than the caprate. 



Preparation. As this acid, unmixed with other volatile acids, 

 occurs in the leaves of Pelargonium roseum, its preparation from 

 that plant is preferable to that from the products of decom- 

 position of oleic and choloidic acids by nitric acid, amongst which 



