958 OILY ACIDS. 



C 35 H 33 O 4 , which is anhydrous palmiticacidC 32 H 31 O 3 plusC 3 H 2 O; 

 the last formula expressing half an equivalent of anhydrous 

 oxide of glyceryl, C 6 H 7 O 5 , from which 3 HO have been sub- 

 tracted.* 



Ethalic acid (page 880), termed also cetylic acid, has abso- 

 lutely the same composition as palmitic acid. 



MARGARIC AND STEARIC ACIDS. 



Margaric acid, or Margarylic acid, 2HO + C 68 H 66 O 6 =2HO 

 4- 2(C 34 H 33 + O 3 ) ; in the last formula C 34 H 33 represents a 

 radical margaryl (Liebig). This acid forms the principal part of 

 the stearopten, or solid portion of human fat and vegetable fixed oils; 

 it is also produced by the dry distillation of ox and mutton suet, and 

 of stearic acid. It is mosteasily obtained in a state of purity, byboil- 

 ing for some minutes stearic acid (the matter composing stearine 

 candles), with an equal weight of nitric acid, of density 1 .273 (32 

 Baume). The mixture is then left to itself, and after expressing 

 the product, which has become concrete on cooling, between 

 folds of blotting paper, it is crystallized several limes suc- 

 cessively from alcohol, till its point of fusion remains constant 

 at 140 (60 centig.). It may also be obtained by adding 

 acetate of lead to the solution of a soap of olive oil, or of human 

 fat ; on treating the precipitate which falls, by cold or hot ether, 

 margarate of lead remains in a state of purity, being insoluble 

 in that menstruum. This salt gives margaric acid, when heated 

 with a dilute mineral acid. (Liebig's Traite). Margaric acid was 

 so named by Chevreul from its pearly lustre ; in external as- 

 pect it greatly resembles stearic acid, but is more fusible, the 

 last acid fusing between 158 and 167 (70 and 75 centig). 



Margarates. In 4he formation of salts of margaric acid, 

 sometimes both its atoms of water, and sometimes only 

 one is replaced by another base. The ether of margaric acid, 

 which contains 2 atoms of oxide of ethyl (Varrentrapp), is ob- 

 tained by saturating with hydrochloric acid gas an alcoholic 

 solution of margaric acid, and withdrawing the excess of hydro- 

 chloric acid by washing the product with water. It fuses at 

 7l.6, is decomposed by alkalies and their carbonates, and also 

 by dry distillation. A mixed soap of oleate and margarate of 



* J'liil. Mag. 3rd scries, xviii. l86. 



