CHEMISTRY. 173 



Hydrogen. 



The generator of water, which consists of 11-75 

 by weight of hydrogen, and 88'23 of oxygen. It 

 was formerly named inflammable gas. It extin- 

 guishes combustion, and is the lightest ponderable 

 matter known. It is in consequence assumed as 

 unity in describing the specific gravity of gases, and 

 the proportions in which they combine. 



Mr. Dobreiner considers hydrogen gas as a metal 

 dissolved in caloric. 



Elements and Weight of Water. 



Oxygen and hydrogen have never been made to 

 unite in any other proportion than that in which they 

 exist in water, which is 1 part, by weight, of hydro- 

 gen, and 7 2 of oxygen. 



A cubic foot of pure water is found at a given 

 temperature to weigh 1000 ounces avoirdupois. 



Water attains its maximum density at the tempera- 

 ture of 42' 3 Fahrenheit. 



Oxygen. 



The generator of acid : thus named because it 

 communicates acidity to whatever it combines with, 

 and it is never found but in combination. It forms 

 the respirable portion (th) of the atmosphere, and is 

 a principal constituent (88 per cent.) of water, and of 

 most acids and metallic oxides. 



To procure pure oxygen from the air, quicksilver 

 may be heated in it at about 600, until it becomes 

 a red powder, which powder,, when ignited, will be 

 restored to the state of quicksilver by giving out 

 oxygen. 



