2 92 PHYSIOLOGICAL PHYSICS. [Chap. xxm. 



capable of holding in solution, while diminished 

 pressure has the same effect. Diminished tempera- 

 ture or increased pressure have the reverse effect. 

 Thus, when a liquid has absorbed its quantity of a 

 particular gas at a certain temperature and pressure, 

 a diminution of the former and increase of the latter 

 will cause an added amount of gas to be absorbed, 

 but not in direct proportion. On the other hand, 

 raising the temperature or diminishing the pressure 

 will cause the liquid to give off some of its absorbed 

 gas. 



The absorptive power of a liquid for a particular 

 gas is independent of other gases which it may already 

 hold in solution. Thus a liquid in contact with a 

 mixture of gases absorbs a quantity of each gas, just 

 as if it were the only one present, the amount being 

 determined by the coefficient of absorption and the 

 pressure of the gas in the mixture. The coefficient of 

 absorption between water and oxygen is '02989, 

 between water and nitrogen is 0-01748 ; the pressure 

 of O in the atmosphere is 0-21 of the total, that of 

 N, 0-79. Thus the ratio of the absorption by water 

 of O and N is as 34 and 66. 



If a liquid containing already in solution a certain 

 amount of CO 2 be exposed to an atmosphere of CO 2 , 

 the absorption of additional gas or the giving off of 

 some already in solution, will be determined by the 

 relation between the pressure of CO 2 in the liquid 

 and in the atmosphere. If the pressure of CO 2 be the 

 same in both, no exchange will be effected ; if, 

 however, the pressure of CO 2 in the atmosphere be 

 greater than in the liquid, absorption will go on till 

 the pressures are equalised ; while, if the excess be 

 on the side of the gas in the liquid, gas will be 

 evolved. Suppose, then, a liquid containing already 

 in solution both O and CO 2 be exposed to an atmo- 

 sphere of mixed gas containing also O and C0 2 , any 



