'Chap, xxni] ABSORPTION OF GASES. 291 



C0 2 could escape, and so the mercury fell in the tube. 

 Where the septum separated gas at different pressures, 

 the effect of the diffusion was to restore equilibrium ; 

 that is, the diffusion went on until the pressure on 

 each side of the septum was the same, and the rate of 

 diffusion was greater the greater the difference of 

 pressure on the two sides. Suppose, then, a septum 

 to separate two masses of mixed gases, each mixture 

 containing O and CO 2 , the partial pressure of O being 

 great and of CO 2 small on one side, and that of O 

 small and CO 2 great on the other, the result would 

 be an exchange between the two mixtures through 

 the septum, passing in one direction and CO 2 in the 

 other, till the partial pressure of each gas was the 

 same on each side of the septum. 



Absorption of gases toy liquids. Gases may 

 be absorbed by liquids and retained in solution by 

 them. Graham concludes "that gases may owe their 

 absorption by liquids to their capability of being 

 liquefied and to the affinities of liquids (apparent in 

 their miscibility), to which they become in this way 

 exposed," and that " solutions of gases in liquids are 

 mixtures of a more volatile with a less volatile liquid ; 

 and to them may be extended the laws which hold in 

 such liquids." It is found that the gases most readily 

 liquefied are those which are absorbed in greatest 

 amount. Thus carbonic acid gas, ammonia, sulphur- 

 ous acid gas, hydrochloric acid gas are at once easily 

 liquefied and absorbed, while oxygen, nitrogen, and 

 hydrogen, liquefied with difficulty, are feebly absorbed. 

 Different liquids absorb different quantities of the 

 same gas. The coefficient of absorption or solubility 

 of a gas is the volume of the gas absorbed by unit 

 volume of the liquid at C. and 760 mm. pressure. 

 The amount of gas absorbed by the same liquid varies 

 with the temperature and pressure. Increased 

 temperature diminishes the amount the liquid is 



