﻿510 Molecular Dimensions of Sulphur Dioxide. 



We have t 18 = 73*03 sec., and t 100 = 94*99 sec. 

 The ratio of the viscosities at 18°0 C. and 100 o, C. is 

 given by the ratio of these times ; thus 



??ioo *ioo 94*99 

 i7i 8 t 18 73-03 



Assuming Sutherland's law to hold over the range of 

 temperature used in these experiments, the value of: Suther- 

 land's constant is 416. The validity of Sutherland's law for 

 this gas over the range of temperature investigated cannot 

 be expected to be great on account of the probable large 

 deviations from Boyle's law which this gas may exhibit, 

 since the temperatures at which measurements have been 

 made are not very far removed from the boiling-point of 

 liquid sulphur dioxide. The value of C given, and subsequent 

 deductions depending thereon, should therefore be accepted 

 with some reserve. 



Also at 18°'0 0,, * s ° 2 = ^^ =0-6923. 

 t air 105*53 



(Correcting for slip in the usual way, we obtain 



25^=0-6908. 



Assuming that the viscosity of air at 18 o, C. is 1*814 x 

 10~ 4 C.Gr.S. units, the values for S0 2 are 



i/ 18 =l-253x 10- 4 C.G.S. units, 



Vm = 1-630 x 10~ 4 C.G-.S. units, 



.and by extrapolation, using Sutherland's law, 



Vo = 1-168 xl0- 4 O.G.S. units. 



According to the usual works of reference and published 

 papers, Vogel * is the only modern worker on this subject, 

 and he found that ^ = T183 x 10~ 4 C.G.S. units. 



Calculation of Molecular Dimensions. 



The above results enable us to calculate for sulphur dioxide 

 that mean area which is interpreted by Professor Rankine f 

 as the area which the molecule presents in mutual collision 

 with others. Chapman's % formula, modified in its interpreta- 

 tion, as indicated above, is the basis of this calculation. The 



* H. Vogel, Berlin Diss. p. 46, 1914. 



t Proc. Faraday Soc. vol. xvii. part 3 (1922). 



X Chapman, Phil. Trans. A. vol. ccxvi. p. 347. 



