176 EQUILIBRIUM OF HETEEOGENEOUS SUBSTANCES. 



pressure may by (263) be expressed by the formula , the relative 

 density of a binary gas-mixture may be expressed by 



n.t. 



(326) 



JJV 



Now by (263) a.m, + a 2 m 2 =^. (327) 



L 



By giving to m 2 and m a successively the value zero in these equations, 

 we obtain 



A=2s, A=A (328) 



<! U< 2 



where D 1 and D 2 denote the values of D when the gas consists wholly 

 of one or of the other component. If we assume that 



A = 2A, (329) 



we shall have a 1 = 2a 2 . (330) 



From (326) we have m, + m 2 = D , 



a s t 



and from (327), by (328) and (330), 



whence mi = (A-) (331) 



(332) 



By (327), (331), and (332) we obtain from (320) 



A , B' C , QQQ x 



= log^ -- : (333) 



T 

 2 (D - D^a, a 2 



This formula will be more convenient for purposes of calculation if 

 we introduce common logarithms (denoted by Iog 10 ) instead of hyper- 

 bolic, the temperature of the ordinary centigrade scale t c instead of 

 the absolute temperature t, and the pressure in atmospheres p at instead 

 of p the pressure in a rational system of units. If we also add the 

 logarithm of a s to both sides of the equation, we obtain 



where A and denote constants, the values of which are closely 

 connected with those of A and G. 



From the molecular formulae of peroxide of nitrogen N0 2 and 

 N 2 4 , we may calculate the relative densities 



= 1-589, and A = *0691 = 3'178. (335) 



