96'4 OILY ACIDS. 



vapour of anhydrous sulphuric acid, and the compound losing 

 the elements of one atom of water forms a new acid, of which 

 the salt of lead is expressed by 4 PbO + C 8 H 2 S 2 O 10 . 



Succinates. The constitution of this class of salts is still 

 doubtful. According to Fehling the acid is really tribasic, 

 3HO+C 8 H 3 O 5 ; the basic salt of lead dried at 428 being 

 3PbO + C 8 H 3 O 5 . In the salt of silver and other succinates 

 only two atoms of metallic oxide are found, the third atom of 

 base being water. Neutral succinate of ammonia is much used 

 to separate peroxide of iron from oxide of manganese and other 

 metallic oxides ; both the reagent and metallic solution must be 

 exempt from free acid, as otherwise the succinate of iron will 

 dissolve in the washings. The formula of succinamide is NH 2 

 4-C 4 H 2 O 2 , of bisucdnamide NH 2 + C 8 H 3 O 4 . The last com- 

 pound when dissolved in water assumes 2 HO, and forms fine 

 rhomboidal crystals; the solution of these crystals has no 

 action upon metallic salts, and therefore does not contain suc- 

 cinic acid. 



SECTION II. 



OLEIC ACID AND ACIDS RELATED TO IT. 



This acid has been less successfully investigated than stearic 

 acid, and is probably a mixture of two different principles as it 

 is generally obtained. It forms the essential part of the fat oils 

 which are not drying, such as oil of olives and oil of almonds, 

 from the last of which it is most advantageously prepared, and 

 is found in less considerable quantity in tallow, solid fats, human 

 bile and old cheese. The acid derived from a soap of the fat 

 oil of sweet almonds is mixed with its weight of pulverised 

 oxide of lead, and after the mixture is digested on a water-bath 

 for several hours, twice its bulk of ether is added to it, and the 

 whole left to itself for 24 hours. There is thus formed mar- 

 garate of lead which is insoluble, with an acid oleate of the 

 same base, which is soluble in ether. The ethereal solution is 

 then decomposed by dilute hydrochloric acid, which sets at 

 liberty the oleic acid ; the last coming to the surface of the 

 mixture with the ether, and forming an oily limpid stratum. 

 The ether is expelled by evaporation, and the oleic acid saponi- 



