MR H. BRERETON BAKER ON COMBUSTION IN DRIED OXYOBt 589 



that amorphous phosphorus combines with oxygen at a lower temperature than that 

 at which it is changed to the ordinary modification when heated in an inert gas. The 

 statement which is ordinarily made that amorphous phosphorus, when heated to 260, 

 is converted into the yellow variety and if this is done in air or oxygen it then 

 catches fire, is incorrect. Amorphous phosphorus must be considered as undergoing 

 a true combustion, very slow at ordinary temperatures, slow at 100, and quick at some 

 temperature just below 260. 



Combustion of Tellurium in Oxygen. 



The tellurium was purified by dissolving it in fuming sulphuric acid. The deep red 

 solution was precipitated by the addition of water. It was thought that the possi- 

 bility of occluded hydrogen being present would be obviated in this way. As has 

 been shown, hydrogen has a great influence in bringing about combustion in dried 

 gases, and its elimination was made a principal object in these purifications. The 

 precipitated tellurium was washed with distilled water several times, and dried by 

 heating in vacuo over phosphorus pentoxide. 



It was placed in hard glass tubes in oxygen dried (1) for two, (2) for three weeks, 

 but in both cases, when heated over an Argand burner with comparison tubes filled 

 with moist oxygen, combustion appeared to take place with as much readiness as was 

 the case when moisture was present. 



Combustion of Selenium. 



Selenium was purified by several sublimations, at first in vaciu>, then in selenium 

 chloride vapour. It was then freed from all traces of the chloride by repeated subli- 

 mations in vacuo, pieces of solid potash being present. 



Tubes were prepared containing this purified selenium in pure oxygen. In some of 

 them the oxygen was dried by phosphorus pentoxide, while in the others the oxygen 

 was saturated with aqueous vapour. 



Experiment I. A tube containing selenium in oxygen, which had been standing 

 in contact with phosphorus pentoxide for two weeks, was heated with a similar tube 

 containing selenium in moist oxygen. The dry selenium began to burn at the same 

 moment as the moist, with a slightly less intense flame. On analysis the oxygen was 

 found to be totally used up in both tubes. 



Experiment II. The tube containing selenium in oxygen, dried by phosphorus 

 pentoxide, was allowed to stand for two months. It was supported above an Argand 

 burner with a tube containing selenium in moist oxygen. No difference could be 

 observed between the combustion of the moist and dry substances. 

 Selenium, therefore, when purified in this way, burns in dry oxygen. 



