72 THE BUTYRIC ACID GROUP 



The atomic weight of the hypothetical anhydrous acid = 

 3()875 ; its saturating capacity = 3'239. This acid which was 

 originally discovered by Dumas and Stass,* has subsequently been 

 accurately examined by Smith.f 



If Kolbe's theory be applicable to this acid, cetylic acid must 

 be regarded as C 30 H 31 .C 2 O 3 .HO, which would explain why it 

 differs from the isomeric palmitic acid. Two isomeric acids can- 

 not appropriately be placed in the same group ; hence we place 

 cetylic acid here instead of considering it with the solid fatty acids. 

 We also find in this relation an additional reason why the solid fatty 

 acids whose general formula may be regarded as = C n H n _ 1 O 3 .HO, 

 should not be regarded as simple continuations or ascending 

 members of this group. 



Combinations. The alkaline salts of this acid are soluble in 

 water, and crystallise readily in white nacreous scales. 



Preparation. Spermaceti, from which this acid is obtained, is a 

 haloid salt like the other fats, but instead of this acid being com- 

 bined with oxide of lipyl, it is united to another haloid base en- 

 tirely corresponding with the ethers of pure chemistry ; this haloid 

 base when treated with solid caustic alkalies is converted into 

 cetylic acid. We obtain the acid which exists pre-formed in the 

 spermaceti, by saponifying the latter with a caustic alkali, decom- 

 posing the soap with hydrochloric acid and digesting the newly 

 formed mixture of cetylic acid and ethal (C 32 H 33 O.HO) with milk 

 of lime ; the ethal is then extracted with cold alcohol while the 

 cetylate of lime remains. The lime-salt is then decomposed by 

 hydrochloric acid, and the separated cetylic acid purified by solu- 

 tion in ether. 



This haloid base, ethal or hydrated oxide of cetyl, which is 

 obtained on the saponification of spermaceti, bears exactly the 

 same relation to cetylic acid that alcohol bears to acetic acid or 

 fusel oil to valerianic acid. Moreover, as we shall further more 

 fully describe, cetylic acid may in a similar way be prepared from 

 this body by heating one part of it in six parts of a previously heated 

 mixture of equal parts of hydrated potash and caustic lime to a 

 temperature of 210 220 ; in this process, hydrogen is developed 

 and an alkaline cetylate formed (C 32 H 33 O. HO + KO + HO = 

 4 H + KO. C 32 H 31 O 3 ) which must be purified by solution in 

 water and crystallisation, and then combined with baryta, from 



* Ann. dc Chim. et de Phys. T. 72, pp. 5-11. 

 t Ann. d. Ch. u Pharm. Bd. 42, S. 4051. 



