THE DYNAMICAL THEORY OP GASES. 61 



The discussion of the interdiffusion of three or more gases leads to a much 

 more complicated equation than that which we have found for two gases, and 

 it is not easy to deduce the coefficients of interdiffusion of the separate gases. 

 It is therefore to be desired that experiments should be made on the inter- 

 diffusion of every pair of the more important pure gases which do not act 

 chemically on each other, the temperature and pressure of the mixture being 

 noted at the time of experiment. 



Mr Graham has also published in Brande's Journal for 1829, pt. 2, p. 74, 

 the results of experiments on the diffusion of various gases out of a vessel 

 through a tube into air. The coefficients of diffusion deduced from these ex- 

 periments are 



Air and Hydrogen '026216 



Air and Marsh-gas , '010240 



Air and Ammonia... '00962 



Air and Olefiant gas '00771 



Air and Carbonic acid '00682 



Air and Sulphurous acid '00582 



Air and Chlorine '00486 



The value for carbonic acid is only one third of that deduced from the 

 experiment with the vertical column. The inequality of composition of the 

 mixed gas in different parts of the vessel is, however, neglected ; and the dia^ 

 meter of the tube at the middle part, where it was bent, was probably less 

 than that given. 



Those experiments on diffusion which lasted ten hours, all give smaller 

 values of D than those which lasted four hours, and this would also result 

 from the mixture of the gases in the vessel being imperfect. 



Interdiffusion through a small hole. 



When two vessels containing different gases are connected by a small hole; 

 the mixture of gases in each vessel will be nearly uniform except near the 

 hole ; and the inequality of the pressure of each gas will extend to a distance 

 from the hole depending on the diameter of the hole, and nearly proportional 

 to that diameter. 



