84 
ME. CLEEK MAXWELL ON THE DYNAMICAL THEOEY OE GASES. 
Putting 
equation (122) becomes 
2 / du dv dw\ 
PiU — 3£ jAog,^, ^ +M 2 -J-3M 2 A 2 )§ 2 2 'i #(3A 2 + 
Similarly, 
P^U— o7c 2 A 2 o 2 q 2 (2M 2 A, + 3M, A 2 ) g x q 2 £( 3 A 2 2 AJ f sfh • 
• (137) 
. (138) 
. (139) 
Since _p=pi+p 2 and q=q x -\-q 2 , where p and q refer to the mixture, we shall have 
p\J = -q=-(q 1 +q 2 ), 
where ^ is the coefficient of viscosity of the mixture. 
If we put s, and s 2 for the specific gravities of the two gases, referred to a standard 
gas, in which the values of j) and § at temperature 0 o are q> 0 and g> 0 , 
,,—_ Po 6 m E ^f + ffPiffg + Gpt • H40) 
r g 0 9 0 " 3A i k l s 1 Epf + Hpj/» 2 + 3 Ag/fgSgGp!’ ^ 7 
where \Jj is the coefficient of viscosity of the mixture, and 
E=-^7( 2 *„A,+S S ,A S ), ' 
F=3A 2 (^ 1 +^ 2 )-(3A 2 -2A 1 )/&^-, 
G= s -^-(2 S ,A, + 3 S A), 
H=3A 2 s 1 s 2 {3£ 1 £ 2 A 2 -]-2£ 2 A 1 }. 
(141) 
This expression is reduced to /a, when y> 2 =0, and to (m 2 when^^O. For other values 
ofyq and j) 2 we require to know the value of £, the coefficient of mutual interference of 
the molecules of the two gases. This might be deduced from the observed values of (Jj 
for mixtures, but a better method is by making experiments on the interdiffusion of the 
two gases. The experiments of Graham on the transpiration of gases, combined with 
my experiments on the viscosity of air, give as values of Jc 1 for air, hydrogen, and car- 
bonic acid, 
Air £,= 4-81 xlO 10 , 
Hydrogen . . . £,=142-8 xlO 10 , 
Carbonic acid . . £,= 3*9 XlO 10 . 
The experiments of Graham in 1863, referred to at page 73, on the interdiffusion of 
air and carbonic acid, give the coefficient of mutual interference of these gases, 
Air and carbonic acid . £=5-2 XlO 10 ; 
and by taking this as the absolute value of £, and assuming that the ratios of the coeffi- 
cients of interdiffusion given at page 7 6 are correct, we find 
Air and hydrogen . . £=29-8xl0 10 . 
