TABLE 125. 

 DIFFUSION OF VAPORS. 



139 



Coefficients of diffusion of vapors in C. G. S. units. The coefficients are for the temperatures given in the table and 

 a pressure of 76 centimeters of mercury.* 



* Taken from Winkelmann's papers (Wied. Ann. vols. 22, 23, and 26). The coefficients for o were calculated 

 by Winkelmann on the assumption that the rate of diffusion is proportional to the absolute temperature. According 

 to the investigations of Loschmidt and of Obermeyer the coefficient of diffusion of a gas, or vapor, at o C. and a 

 pressure of 76 centimetres of mercury may be calculated from the observed coefficient at another temperature and 

 pressure by the formula k = k T (^ n7 , where T is temperature absolute and p the pressure of the gas. The 



exponent is found to be about 1.75 for the permanent gases and about 2 for condensible gases. The following 

 are examples: Air CO 2 , n= 1.968; CO, N 2 O, = 2.o S ; CO 2 H, =i. 742 ; CO O, = 1.785; H O, 

 = 1.755; O N, == 1.792. Winkelmann's results, as given in the above table, seem to give about 2 for vapors 

 diffusing into air, hydrogen or carbon dioxide. 

 SMITHSONIAN TABLES. 



