(0 THE DYNAMICAL THEORY OF OASES. 



Time. $ 







T -01193 



2T '02305 



3J -03376 



4T -04366 



5T -05267 



67 1 '06072 



-07321 

 -08227 

 -08845 

 oo -10000 



Mr Graham's experiments on carbonic acid and air, when compared with this 

 Table, give T=500 seconds nearly for a tube 0'57 metre long. Now 



log, 10 a' ,. 



1 " 



T 



whence D = -0235 



for carbonic acid and air, in inch-grain-second measure 



Definition of the Coefficient of Diffusion. 



D is the volume of gas reduced to unit of pressure which passes in unit 

 of time through unit of area when the total pressure is uniform and equal to p, 

 and the pressure of either gas increases or diminishes by unity in unit of 

 distance. D may be called the coefficient of diffusion. It varies directly as the 

 square of the absolute temperature, and inversely as the total pressure p. 



The dimensions of D are evidently DT~ l , where L and T are the standards 

 of length and time. 



In considering this experiment of the interdiffusion of carbonic acid and 

 air, we have assumed that air is a simple gas. Now it is well known that 

 the constituents of air can be separated by mechanical means, such as passing 

 them through a porous diaphragm, as in Mr Graham's experiments on Atmolysis. 



