Gaseous Ammonia, PJiosphine, and Arsine. 



609 



the viscosity measurements had been made; no spontaneous 

 combustion took place. 

 Results : — 



Table III. — Phosphine. 



Each time recorded is the mean of twelve observations, 

 mutually consistent to 0'5 per cent. 



Temperature 



(deg. C.) 



Time of fall 



in seconds. 



Capillary 



Correction 



(«)■ 



0-0397 



Corrected 

 Time 



(t). 



78-73 



Whole pellet. 



Two segments. 



(a) 15-0 



81-99 



85-55 



(b) 150 



81-91 



85-47 



0398 



78-65 



(d) 15 



82-14 



8593 



00123 

 Mean 



78-67 

 78-68 



(c) 100-0 



103-93 



106-13 



0-0270 



101-12 



The ratio of the times of fall for phosphine and air at 

 15° C. is 0'6280. Correcting for slipping coefficients the 

 ratio of viscosities becomes 0*0271, whence for phosphine 



^5 = 0-6271 x 1-799 x 10- 4 = 1'129 x 10" 1 C.G.S. units. 



Also 



/*7ioo\ 



\ "^15 /phosphine 





whence for phosphine 



Vl00 = 1-150 x 10" 4 C.G-.S. units. 



Assuming Sutherland's law to hold over the range of 

 temperature, we obtain for Sutherland's Constant C = 290. 



Arsine. 



This gas was generated by the action of nascent hydrogen 

 on arsenious oxide in an apparatus similar to that used 

 in the case of phosphine. r J lie method of introducing the 

 arsine into the apparatus was also the same, except that 

 after the gas had been solidified at liquid air temperature. 

 and freed from permanent gases by pumping, a mixture of 

 solid carbon dioxide and alcohol was substituted for the 

 liquid air. At this temperature arsine has a considerable 

 vapour pressure, and the vapour was pumped oil', com- 

 pressed, and introduced into the viscometer until the pres- 

 sure was atmospheric. This method was used to ensure 

 that the gas was perfectly dry, — a condition particularly 



