E. ACKERMAN, G. K. STROTHER AND R. L. BERGER 



33 



Fig. 6. Variation of D with 

 fluidity (frnm ref. 4). 



40 eo 80 



FLUIDITY y . POISE"' 



100 120 



The number of encounters of diffusing light molecules of radius ra with 

 a heavy spherical molecule of radius v^ is given by 



where : 



Using: 



Z = 10-3 N47rD (ra + rb) 



Z is the encounter frequency in liters/mole • sec ; 

 N is Avogadro's number in cgs units; 

 D is the diffusion rate in cgs units; and 

 r is in cm. 



fa + I'b — 4 X 10 cm; and 

 D = 2 X 10"5 



one finds that 



Z = 6 X 10 



10 liters 

 mole • sec 



