346 CONSIDERATION OF CARBON COMPOUNDS. 



water and boiling for a short while, when the soap, which is insoluble in the 

 salt solution, rises to the surface and solidifies on cooling. 



Soaps are soluble in water and alcohol ; they contain rarely less than 

 30 per cent., but sometimes as much as 70-80 per cent, of water. 



Ammonia liniment, Linimentum ammonice, and lime liniment, Lini- 

 mentum colds, are obtained by mixing cottonseed oil with water of 

 ammonia and lime-water, respectively. The oleate of ammonium or 

 calcium is formed, and remains mixed with the liberated glycerin. 



Lead plaster, Emplastrum plumbi. Chiefly lead oleate, Pb(C 18 H 33 O 2 ) 2 . 

 Obtained by boiling lead oxide with olive oil and water for several 

 hours, until a homogeneous, pliable, and tenacious mass is formed. 

 Lead oleate differs from the oleates of the alkalies by its complete 

 insolubility in water. 



Wool-fat, Lanolin. This is the fat, or a mixture of fats, found in sheep's 

 wool and obtained by treating the wool with soap-water, and acidifying the 

 wash liquor, when the fats separate unchanged. These fats differ from the fats 

 spoken of above in so far as the alcohol present is not glycerin, but an alcohol, 

 or rather two isomeric alcohols of the composition C 26 H 43 OH and known as 

 cholesterin and iso-cholesterin. These alcohols, which are white, crystalline, 

 fusible substances, when in combination with fatty acids form the compound 

 ethers known as lanolin. 



Lanolin is a yellowish-white (or, when not sufficiently purified, a more or 

 less brownish), fat-like substance, having the peculiar odor of sheep's wool and 

 fusing at about 40 C. (104 F.), forming an oily liquid. Unlike true fats, 

 lanolin is capable of mixing with twice its weight of water or aqueous solutions 

 and yet retaining its fatty consistency ; it is, moreover, much less liable to de- 

 compose than fats, and it is this property and its power to mix with aqueous 

 solutions which have rendered lanolin a valuable agent in certain pharma- 

 ceutical preparations. Official is hydrous wool-fat, the purified fat mixed with 

 not more than 30 per cent, of water. 



QUESTIONS 441. Explain the constitution of simple, mixed, and compound 

 ethers. To what inorganic compounds are they analogous? 442. State the 

 general processes for the formation of ethers and compound ethers. 443. 

 What is the composition of ethyl ether? Explain the process of its manufac- 

 ture in words and symbols, and state its properties. 444. How is acetic ether 

 made, and what are its properties? 445. What is sweet spirit of nitre, and 

 how is it made ? 446. State the general composition of fats and he chief con- 

 stituents of tallow, butter, and olive oil. 447. What is the soli oility of fats 

 in water, alcohol, and ether ; how do heat and oxygen act upon hem ; what 

 is the cause of their becoming rancid? 448. Explain the composition and 

 manufacture of soap, and state the difference between hard and soft soap. 

 449. How are ammonia liniment, lime liniment, and lead plaster made, and 

 what is their composition ? 450. What is the source of lanolin ; what are its 

 constituents and properties ? 



