MIXTURE OF GASES. 107 



until the proportion of the two gases is the same throughout, 

 and the greater the difference of density the more rapidly 

 will the mixture take place. 



Take two different gases, of the same temperature and 

 pressure, contained in separate vessels ; let a communica- 

 tion be established between the vessels, and it will be found 

 that, unless a chemical action take place, the two gases will 

 permeate each other till they are completely mixed, and 

 that, when equilibrium is attained, the pressure of the mix- 

 ture will be the same as before, provided the temperature is 

 the same. Hence, from this experimental fact, the follow- 

 ing proposition can be deduced. 



57. Mixture of Equal Volumes of Gases having 

 Unequal Pressures.// two gases having the same 

 temperature be mixed together in a vessel of volume v, 

 and if the pressures of the gases ivhen respectively con- 

 tained in v, at the same temperature, be p and p', the 

 pressure of the mixture will be p+p'- 



Suppose the gases are separate. Take the gas whose 

 pressure is p, and change its volume until its pressure is p', 

 its temperature remaining the same. Its volume will then 



v 

 be, by Mariotte's law (Art. 48), , v. 



Now let the two gases be mixed without change of vol- 

 ume, so that the volume of the mixture is 



then the pressure of the mixture will be p', according to the 

 preceding experimental fact (Art. 56). Now if the mixture 

 be compressed till its volume is v, its temperature remain- 

 ing constant, the pressure will become, by Mariotte's law, 



P + P'> 



This result is equally true for a mixture of any number 

 of gases. 



