﻿510 Dr. T. Ewan on the Rate of Oxidation 



the equation may be brought into the form 



This can be easily integrated between the limits P and P, 

 and gives : — 



*- ! £ J +(*5=3IS-i-&-i&-'*] 

 . ♦(w5)Bt+6**'] 



+ &-%/ &c ^ 



For phosphorus at ordinary temperatures, p' is so small 

 compared with a that the equation may, without appreciable 

 error, be written 



('°*fe)[?-a- • • ^ 



The values of K in the fifth column of Table I. have been 

 calculated by means of this equation. The numbers are more 

 nearly constant than those obtained by means of the uncor- 

 rected equation (I). 



It appears, therefore, from these experiments that the 

 velocity of the reaction is proportional to the pressure of the 

 oxygen. This cannot be true at all pressures, however, for 

 when the pressure of the oxygen is greater than a certain 

 limit the velocity of the reaction becomes zero. 



(b) Phosphorus in Moist Oxygen. Behaviour at Higher 

 Pressures. 



A further series of measurements was therefore made in 

 which the whole range of pressures at which the reaction 

 takes place was studied. 



For this purpose a somewhat different form of apparatus 

 was used. After various trials that shown in fig. 1 was found 

 to be most convenient. The glass vessel EPA (50-70 cubic 

 centim. capacity) was conected by means of a capillary tube 

 (J millim. diameter) with the tap B and with the mano- 

 meter D. The joint at C was usually made by means of a 

 ground-glass joint luted with mercury ; occasionally a thick 

 indiarubber tube was used. The manometer was arranged 

 so that the mercury always stood at the same height in 

 the limb D, the volume of the apparatus therefore remained 

 constant. A mercury- gauge was mostly used, but some of the 

 experiments at lower pressures were made with a manometer 



