91 VISCOSITY OF GASES 241 



calculated with the density of water for nnit, for which we 

 obtain at the temperature of freezing-point 



A = 1-5198/ 773-3 = 0-0019653 

 and at the temperature $ 



A = 0-0019653/(l + 0,3), 



where a = 0-00367 is the coefficient of expansion. 



If we put this value of A in the formula for a, we obtain 

 from the given values of a, first the corresponding values of 



and thence those of the ratio which the two coefficients of 



viscosity bear to each other : 



3- = 32-6 s = 0-8482 17, /i? 2 = 0-634 

 35 8550 637 



40-3 8236 621 



If we now employ the formula for b in the same way 

 we find also the absolute values of the two coefficients of 

 viscosity, firstly that of TJ I for the gas when perfectly 

 dissociated into the simple molecules C0 2 , and then that of 

 rj 2 for the gas when containing only the double molecules 

 C 2 H 4 , thus, 



3 = 32-6 7 7l = 0-000142 rj 2 = 0-000224 

 35 148 232 



40-3 151 244 



These numbers refer to the temperatures placed opposite 

 them. I have therefore reduced them to C. by assuming 

 for C0 2 the temperature-factor 



1 + a&, 



which holds approximately ( 85) for ordinary carbonic acid, 

 and, on the contrary, for C 2 4 the temperature-function 



which holds for vapours (87). I have thus obtained for 

 the temperature C. the following values : 



Vl = 0-000127 77, = 0-000189 



131 194 



132 198 



which exhibit a fairly satisfactory agreement. 



E 



