594 CYRUS Fi TOLMAN 
The atmosphere, of course, is not pure CO,, but a mixture 
of gases in the following proportions : Oxygen, 20.9 vol.; nitro- 
gen, 79.1 vol., of which 01.18 per cent. belongs to that group 
of gases called argon,’ CO, .03 vol. 
At any given temperature the amount of the atmospheric 
gas dissolved in pure water is the product of the amount dis- 
solved under 760™™" pressure of the pure gas by the partial 
pressure of gas in the air. This holds for the carbon dioxide in 
spite of the chemical reaction CO, + H,O ——= COR hs 
may be seen as follows: 
Let a, 4, and ¢ be the concentrations respectively of CO,, 
iO yand hy, COZ ithenretone 
b 
=: Ky, 
G 
but the water is so greatly in excess that its concentration, 4, can 
be considered as a constant (K,) or 
& 
a 
Therefore the amount H,CO, |c]| varies directly with the amount 
CO, [a] dissolved, and this is proportional to the partial pressure 
of the gas. Making the calculations from Dittmar’s tables, we 
find that one liter of pure water at 15° C. dissolved from the 
atmosphere).32° of €@O,,.7.2 of oxygen, and 13.2..01 angen 
and nitrogen.’ 
The absorption of gases in salt solutions.—The researches of J. 
Setchenow? show us that a gas dissolved in salt solution obeys 
the same laws as if the salt were not present, if there is no 
chemical reaction between the gas, the salt,and the solvent. In 
this case, however, the attractive power between the molecules 
of the solvent and the gas is partially satisfied by the salt mole- 
«Chem. News, 72 p. 308. Comptes Rendus de |’ Academie des Sciences, CX XI, 
p. 605. 
?Challenger Reports, Vol. I, pp. 167-168. 
3 Ann. de Chemie: pp. 226-270. 
