Sulphuretted Hydrogen and Cyanogen. 619 



Results : — 



Table III. — Cyanogen. 



(The numbers in brackets indicate the number of observations 

 for which the figure quoted is the mean value.) 



Time of fall 

 Temperature 

 (cleg. C). , 



' Whole pellet. 



(a) 17-83 (8) 71-55 



(b) 99-7 (8) 90-69 



in seconds. ■ Capillary 



1 Correction 

 Or). 

 Two segments, : 



Corrected 



Time 



(0- 



(6) 74-73 

 (6) 93-62 



0-0410 

 00303 



68-61 

 87-94 



Making the small corrections to the standard temperatures 

 17°-0 C. and 100°*0 C, we have 



t 17 = 68*41 sees.; £ 100 = 88*01 sees. 

 Therefore (^\ =1*287, whence C = 330. 



\ h7 /Cy 



Also, at 17°*0 C, ~ y = ^^ =0*5518. 



r a ir lZd'yO 



Correcting for slipping, we obtain 



^=0*5505. 



Therefore, for cyanogen, 



^ 7 = 0-995 x 10" 4 C.G.S. units. 



and i7 100 == 1*281 x 10~ 4 C.G.S. units. 



Attention may be called to the considerable variations in 

 the values of the capillary correction in all three cases, and 

 to the consequent necessity for applying it in viscosity 

 measurements with these gases. 



Comparison of Results* 



The collected results are shown in Table IV., together 

 with the extrapolated values of the viscosity at 0° C, deduced 

 by assuming Sutherland's law to hold ; and also the mean 

 collision are;is (A), calculated, as indicated in our previous 

 paper (loc. cit.), by means of Chapman's* formula. 



* S. Chapman, Phil. Trans. A. vol. cexvi. p. 279. 

 2 T 2 



