101 DIFFUSION OF GASES 273 



of G' which Sutherland 1 has calculated from von Ober- 

 mayer's experiments on diffusion : 



Carbonic acid air . . . . C' = 250 



Carbonic acid hydrogen . . 106 



Carbonic acid nitrous oxide . 380 



Oxygen hydrogen ... 100 



Oxygen nitrogen . . . . 136 



Oxygen -carbon monoxide . . 124 



As we should expect, these values correspond in magnitude 

 to those which Sutherland has calculated for the simple 

 gases from the observations on viscosity ( 85). 



In the same memoir Sutherland also submits to calcula- 

 tion, in accordance with his theory, the observations which 

 Winkelmann has made on the diffusion of vapours into 

 gases. The same vapours which Lothar Meyer, Schu- 

 mann, and Steudel had employed for their experiments 

 on transpiration ( 86) served also in these experiments. 

 Here also the agreement between the calculations from both 

 series of experiments is satisfactory. 



1O2. Calculation of the Coefficient of Diffusion from 

 the Coefficient of Viscosity 



The agreement between the measurements of the vis- 

 cosity and diffusion goes still further. In the first memoir 

 he published on this theory Maxwell 2 had already deduced 

 from observations on diffusion a value of the free path of 

 gaseous molecules, which harmonises well with the value 

 determined for air from experiments on viscosity. But the 

 connection into which these two different phenomena are 

 brought by the kinetic theory came more strikingly into 

 view when Stefan 3 calculated the numerical values of the 

 coefficients of diffusion directly from the coefficients of 

 viscosity, and thereby found numbers which agreed quite 

 well with Loschmidt's experiments-. 



1 Phil Mag. 1894 [5] xxxviii. p. 1. 



2 Ibid. 1860 [4] xx. p. 21 ; Scient. Papers, i. p. 392. 



3 Wien. Sitzungsber. 1872, Ixv. Abth. 2, p. 323. 



