264 HYDROGEN. 



salts of soda and lime does not increase with the temperature, 

 like that of other salts. 



Water is also capable of dissolving a certain quantity of air 

 and other gases, which may again be expelled from it by boiling 

 the water, or by placing it in vacuo. Rain-water generally 

 affords 2i per cent of its bulk of air, in which the proportion 

 of oxygen gas is so high as 32 per cent, and in water from 

 freshly melted snow 34.8 per cent, according to the observa- 

 tions of Gay-Lussac and Humboldt, while the oxygen in atmo- 

 spheric air does not exceed 21 per cent. Boussingault finds 

 that the quantity of air retained by water, at an altitude of 6 or 

 8000 feet, is reduced to one third of its usual proportion. 

 Hence it is that fishes cannot live in Alpine lakes, the air con- 

 tained in the water not being in adequate quantity, for their 

 respiration. The following table exhibits the absorbability 

 of different gases by water deprived of all its air by ebul- 

 lition : 



100 cubic inches of water at 60 and 30 Bar., absorb of 



Dalton and Henry. Saussure. 



Sulphuretted hydrogen . 100 C. I. . 253 



Carbonic acid . . 100 . .106 



Nitrous oxide . . 100 . 76 



Olefiant gas . . . 12.5 . 15.3 



Oxygen ... 3.7 . 6.5 



Carbonic oxide . . 1.56 . . 6.2 



Nitrogen 1.56 . . 4.1 



Hydrogen . . 1.56 . . 4.6 



The results of Saussure are probably nearest the truth, for 

 sulphuretted hydrogen and nitrous oxide, but for the other 

 gases those of Dalton and Henry are most to be depended on. 



Uses. Rain received after it has continued to fall for some 

 time may be taken as pure water, excepting for the air it con- 

 tains. But after once touching the soil, it becomes impregnated 

 with various earthy and organic matters, from which it can only 

 be completely purified by distillation. A copper still should 

 be used for that purpose, provided with a copper or block tin 

 worm, which is not used for the distillation of spirits, as traces 

 of alcohol remaining in the worm and becoming acetic acid, 

 cause the formation of acetate of copper, which would be washed 

 out and contaminate the distilled water. The use of white lead 



