﻿Attraction of Unlike Molecules. 11 



H 2 . N, O., CO.,. N 2 0. CO. 



46[68] 247 245 839 755 198 



The value 68 for H 2 is the experimental one, which is very 

 uncertain ; the value 46 would bring H 2 into accord with 

 all other bodies, as may be seen in the " Viscosity of Gases 

 and Molecular Force/' 



The most natural relation to expect between jA^^, 2 A 2 ??2 2 2 , 

 and l A 2 m l m 2 is 1 A 2 m l m 2 = ( 1 A 1 ?n 1 2 2 A 2 m 2 2 )^ and accordingly 

 we now give values of 10" l (M 1 £ 11 C 1 M 2 /8 2 2C 2 )^ obtained 

 from the numbers just given, and the ratio of 



10- 1 1 C 2 {(M 1 j8 1 )i/2+ (M 2 ]8 a )V2} 8 given above to 

 lO-^M^AMj&A)*. ' 



C0 2 &N 2 . C0 2 &H 2 . C0 2 &N 2 0. 



lO-^M^AM^aOa)* 455 196 796 



Eatio 1-4 "92 14 



2 &H 2 . 2 &N 2 . 2 &CO. 



lO-HM^AMAA)^ 106 246 220 



Eatio 1-2 1-16 11 



The mean value of the ratio is 1*2, and the departures of 

 some of the individual numbers from the mean, though large, 

 are not larger than could be caused by only slight error in 

 the experiments or the theory, for it must be remembered that 

 the constants xC 2 occur in equation (8) in such a manner as 

 to make their values when calculated from that equation very 

 sensitive to small errors in the ratio of the diffusion-coefficients 

 at two temperatures. Thus, notwithstanding the high degree of 

 accuracy attained by v. Obermayer in his elaborate experiments, 

 it must be allowed that the last series of numbers is as nearly 

 constant as can be expected. To show this clearly it will be 

 best to assume that the ratio is 1, and calculate 1 C 2 from the 

 equation 



iCW(MA)*/2 | (^/SMMAAMA)*, • (9) 



and then by the equation (8) calculate values of the ratio of 

 the diffusion-coefficients at v. Obermayer's two temperatures 

 for comparison with his experimental values : — 



CO a &N 2 . C0 2 &H 2 . C0 2 &N 2 0. 2 &H 2 . 2 &N 2 . 2 &CO. 

 Exper. ... 1-41 133 140 1'31 132 1-43 



Theory... 1-38 134 1-38 131 1-32 143 



The largest discrepancy between theory and experiment 

 amounts to 2 per cent., and it cannot be claimed that the 

 ratio of the diffusion-coefficients at two temperatures, as 

 measured experimentally, can be guaranteed correct to within 

 2 per cent., especially as the experimental measurements only 



