692 Research Staff of the G. E. C., London, on the 



(3) The adhesion is not due primarily to chemical reaction, 

 although such reaction (as in the conversion of CO to C0 2/ ) 

 may aid adhesion by converting the gas into another which 

 adheres more readily. 



(4) The discharge can also liberate gas from the walls, 

 doubtless by bombardment of the charged particles, and 

 some of the gas so liberated cannot be libeiated by heating 

 the glass to the softening point. 



(5^ The limit in the disappearance of the gas is reached, 

 when the rate at which gas is caused to adhere to the glass 

 by the discharge becomes equal to the rate at which it is 

 liberated by the bombardment. 



The Action of Phosphorus. 



The main object of the research was to elucidate the 

 well-known action of phosphorus in promoting the dis- 

 appearance of gas. The experiments so far described were 

 undertaken in the hope that they would throw light on that 

 action. We must now proceed to discuss what happens 

 when phosphorus is present in the discharge vessel. 



' 19. The physical properties of phosphorus. — It is well 

 known that phosphorus exists in at least two forms at room 

 temperatures — the white and the red ; the red is stable, the 

 white metastable. The transition point is usually given as 

 520° K., and heating to just below this temperature is 

 necessary to convert the white rapidly into red. On the 

 other hand, the conversion of red into white does not proceed 

 rapidly attempertures below 720° K., which is just above the 

 softening point of the glass used. It was not possible to 

 convert red into white rapidly without passing the softening 

 point of the glass ; but a slow conversion doubtless takes 

 place at lower temperatures. 



At room temperature the red phosphorus has a vapour- 

 pressure too low to be determined by any of the ordinary 

 methods. In the course of the experiments a rough determi- 

 nation of the vapour-pressure of white phosphorus at 290° K 

 was made by a modification of Victor Meyer's method. For 

 this purpose an evacuated vessel was filled with the vapour, 

 and then placed in communication for a few seconds through 

 n narrow tap with a vessel containing a neutral gas at a known 

 greater pressure. If it is assumed that no phosphorus diffuses 

 out against the entering stream of gas, the vapour-pressure can 

 be calculated from the amount of that gas entering. It was 

 found that at 290° K. the vapour-pressure was 0*014 mm. 

 No previous measurements at such low temperatures could 



