ETHERS. 309 



Soap. Any fat boiled with sodium or potassium hydrate will 

 form soap. Soft soap is potassium soap, hard soap is sodium 

 soap. The better kinds of hard soap are made by boiling olive 

 oil with sodium hydrate : 



C 3 H 5 3(C 18 H 33 2 ) + 3NaHO = 3(NaC 18 H 33 O 2 ) 4- C 3 H 5 3HO. 



Oleate of glyceryl Sodium Sodium oleate Glycerine, 



(olive oil). hydrate. (hard soap). 



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, Linimentiim ammonice, and lime liniment, Lini- 

 mentiim calcis, are obtained by mixing cottonseed oil with water 

 of ammonia and lime-water, respectively. The oleate of am- 

 monium or calcium is formed, and remains mixed with the 

 liberated glycerine. 



Lead plaster, Emplastram plumbi. Chiefly lead oleate, 

 Pb2C 18 H 33 2 . Obtained by boiling lead oxide with olive oil and 

 some water for several hours, until a homogeneous mass is 

 formed. Lead oleate differs from the oleates of the alkalies by 

 its complete insolubility in 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 com- 

 pound ethers. 



443. What is the composition of ethyl ether ? Explain the process of 

 its manufacture 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. 



447. What is the solubility of fats in water, alcohol, and ether; how 

 do heat and oxygen act upon them ; what is the cause of their becoming 

 rancid ? 



448. Mention the chief constituents of tallow, butter, and olive oil. 



449. Explain the composition and manufacture of soap, and state the 

 difference between hard and soft soap. 



450. How are ammonia liniment, lime liniment, and lead plaster 

 made, and what is their composition ? 



