CHEMISTRY. 41 



OXYGEN ITS PROPERTIES AND RELATIONS. 



Oxygen is an invisible, transparent fluid, without taste or 

 odor ; respirable and necessary to organic life, with a specific 

 gravity of 1.2G, air being 1. It has the most extensive 

 affinity of all known substances. It combines with metals, 

 forming oxides and acids : it combines also with other gases, 

 and is an important element in water and the atmosphere: it 

 js usually called a supporter of combustion, it exists in great 

 abundance in nature, and may be obtained by chemical process 

 from several substances, most easily, perhaps, from black 

 oxide of manganese. It is said that nearly one-third of the 

 weight of all the solid matter of the globe consists of this 

 gas. The combustion of all fires depends on the presence of 

 oxygen, a lighted taper burns with greatly increased bril- 

 liancy in pure oxygen gas. 



No plant can vegetate without it, although no plant will 

 long survive after being placed in this gas alone. No animal 

 can respire for a single minute without oxygen, but when 

 immersed in a jar of it, the vital processes are all increased 

 until fever succeeds, and the animal dies. "According to 

 Dr. Henry, 100 volumes of water absord only 3j of oxygen.'' 

 The combining number of oxygen is 8. 



HYDROGEN ITS PROPERTIES AND RELATIONS. 



Hydrogen gas is the lightest of all known substances, being 

 fourteen times lighter than common air, destitute of taste, 

 color or odor : it is combustible, but not a supporter of com- 

 bustion; it is incapable of sustaining animal life, though it 

 is destitute of poisonous properties, an animal dies when 

 immersed in it from want of oxygen, the death results from 

 its negative condition, rather than from any positive injury 

 which is sustained by breathing the gas. It exists in nature 

 in less abundance than carbon or oxygen, and is not known to 

 occur in a free or uncombined state. It forms a small part of 

 all animal and vegetable substances, and constitutes one-ninth 



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