SEBACIC ACID. ?7 



1150; its saturating capacity 8-696 ; its rational formula is 

 C 8 H 8 .C 2 3 .HO. 



Combinations. Its salts are very similar to those of benzoic 

 acid; the alkaline salts are very soluble, the earthy salts are 

 difficult of solution, while those of the oxides of the heavy metals 

 are insoluble. 



Pyrotartaric acid, C 5 H 3 O 3 .HO, is formed when nitric acid acts 

 on sebacic acid, each atom of the latter assimilating 5 atoms of oxy- 

 gen, thus C 10 H 8 O 3 +5O=2(C 5 H 3 O 3 .HO); itis cry stallisable, white, 

 resists the action of the air, fuses at a little above 100, and 

 sublimes at a higher temperature, developing at the same time a 

 white suffocating vapour ; it has a strongly acid taste, dissolves 

 readily in water, alcohol, and ether, and in sulphuric acid without 

 blackening, and expels carbonic acid from its salts ; most of its 

 salts are soluble in water and in spirit of wine; with neutral 

 acetate of lead it yields no precipitate, but with the basic acetate, 

 and with nitrate of silver, we have a white, gelatinous deposit 

 which, on drying, becomes brownish white, and translucent. This 

 acid is isomeric, or probably identical, with the lipic acid which has 

 been examined by Laurent and Bromeis, and is mentioned in page 

 74 ; hence it belongs to the same group of acids as sebacic acid. 



Preparation. This acid is formed during the dry distillation of 

 oleic acid. As it is produced from no other kind of fat, we may 

 determine the presence and amount of olein in a fat, from the 

 presence and amount of the sebacic acid. In order to prepare it, 

 the distillate must be boiled with water as long as crystals continue 

 to be deposited from it on cooling. By a repetition of the crystal- 

 lisation, the acid may be obtained in a state of purity. 



Tests. In this distillation scarcely any other acid can occur 

 which could be confounded with sebacic acid. It can be distin- 

 guished from benzoic acid, to which, as we have observed, it is very 

 similar, by the circumstances that there is a precipitate on the 

 addition of nitrate of silver or of one of the salts of the suboxide of 

 mercury to its hot solution (which is not the case with benzoic 

 acid ;) that the sublimed acid crystallises far less readily ; that a 

 microscopic examination of the crystals obtained from the aqueous 

 solution, reveals a difference of form; and finally that by the 

 action of nitric acid it is converted into lipic acid. 



