New Generalized Equation for Gas Diffusion Coefficient.

THE IMPORTANCE of diffusion in chemical processes has been well known. In view of the scarcity of reiiable experimental data for the diffusion coefficient, its value was often obtained from the correlation equations. During the past years, there were many investigations. The theoretical approach to this study was due to Fick (9) , Stefan (27), Maxwell (19), Sutherland (28), Meyer (20), Jeans (13), Enskog (7), and Chapman and Cowling ( 4 ) . The empirical or modified correlation equations have been developed by Arnold ( I ) , Gilliland ( I O ) , Hirschfelder, Bird, and Spotz ( I I ) , Slattery (24 ,25 ) , and others (8, 33). The most reliable one is the Chapman and Cowlings’ equation, which has been extensively investigated by Hirschfelder, Bird, and Spotz (12). Although the values calculated by the Chapman and Cowlings equation agree well with the experimental measurements, its use is somewhat cumbersome because it involves a long table for the collision integral function. For rapid calculations and for use in analytical solutions of the diffusion problem, a simpler and more generalized equation is still needed. The present investigation aimed to review briefly previous recent work, then to propose a new, simple, convenient, and more generalized equation for the gas diffusion coefficient of a binary system a t low pressure, and finally to compare the result with those of previous investigators.