52 ANSWMliS TO PRACTICAL QUESTIONS 



1 6. What proof have we that H is a metal? 



Besides that given in the Chemistry, the " sodium amalgam" 

 is thought by some to be an additional proof. Heat moderate- 

 ly in a test-tube a little mercury with a grain or two of sodium. 

 The two metals will combine, forming a pasty amalgam. 

 When cold, pour over it a solution of sal-ammoniac. The 

 amalgam will immediately swell up to eight or ten times its 

 original bulk, retaining, however, its metallic lustre. It is 

 thought that H is the metal which puffs out and combines 

 with the mercury, since otherwise we would be compelled to 

 suppose that NH 4 is a metallic element, instead of a com- 

 pound radical, as is generally believed. 



17. Why does not frozen meat spoil? 



The cold protects from chemical change. The bodies of 

 mammoths have been found in the frozen soil of Arctic regions 

 so perfectly preserved that the dogs ate the flesh. How long 

 the animals had been there we cannot tell, but certainly for 

 ages. In 1861 the mangled remains of three guides were 

 found at the foot of the Glacier de Boissons, in Switzerland. 

 They had been lost in an avalanche on the grand plateau of 

 Mont Blanc, forty-one years before. 



1 8. Give an illustration of the effect of food on the disposi- 

 tion of animals. 



Bears which feed on acorns are mild and tractable, while 

 those of the polar regions, which live on flesh alone, are fierce 

 and ungovernable. 



19. Compare the chemical action of the animal with that of 

 the plant. 



The animal lives on organized materials, taking up O and 

 evolving CO 2 , and other oxydized products. The plant lives 

 on unorganized materials, CO 2 , HO, NH,, and salts, organ- 

 izing them and evolving O. The function of the animal is 

 oxydation; that of the plant, reduction. The food of the 

 plant serves merely to increase its bulk ; that of the animal is 

 employed to replace the material worn out by the active opera- 

 tions of life. The animal obtains the energy necessary for its 



