MR. H. BRERETON BAKER ON COMBUSTION IN DRIED OXYGEN. 585 



When no more gas was evolved, the tube was removed from the pump and sufficient 

 phosphorus trichloride added to cover the phosphorus. The chloride was boiled and 

 the tube sealed. It was heated in an air bath to 200 for three days. Any traces of 

 phosphine or hydrogen would attack the chloride of phosphorus with fonnation of 

 hydrochloric acid and free phosphorus. The tube was opened and the phosphorus 

 chloride distilled off. To get rid of hydrochloric acid, the phosphorus was heated in a 

 vacuous tube which had a piece of solid potash at the other end. 



To get rid of any traces of ordinary phosphorus which might have been formed in 

 these processes, a stream of purified air was drawn over the purified substance heated 

 to 100 for two days. 



Tubes were constructed like those used for carbon, with plugs of phosphorus pent- 

 oxide at one end and purified amorphous phosphorus at the other. These tubes were 

 each heated over an Argand burner with a similar tube containing the same phos- 

 phorus in moist oxygen. In six of them, which had been drying from 2-5 weeks, no 

 visible combustion could be observed, though the temperature was raised sufficiently 

 nigh to distil the phosphorus. It condensed in yellow globules which could again be 

 distilled, confirming the last results obtained on the influence of moisture on 

 the combustion of ordinary phosphorus. After the experiments the gases were 

 analysed, and found to consist of pure oxygen. In one experiment the tube had been 

 standing for two months. The phosphorus pentoxide was very moist, and it was 

 thought probable that the gas would not be sufficiently dry to prevent combustion. 

 The end of the tube containing the phosphorus was heated over a -inch flame of an 

 Argand burner, side by side with a comparison tube of phosphorus in moist oxygen. 

 In a little tune the moist phosphorus burnt with a bright white light. The dry 

 phosphorus began to distil slowly. When the heavy white vapour reached the moist 

 oxide of phosphorus it burnt with a green flame quite slowly, the flume repeatedly 

 going out and being re-kindled. The flame never moved to any other point, but 

 burnt in this position until all the oxygen was used up. 



These experiments show that phosphorus, both in the crystalline and the amorphous 

 state, does not undergo combustion when heated in dry oxygen. 



Tlie Temperature required for the Combustion of Amorphous Phosplwrus. 



It was frequently noticed that amorphous phosphorus burnt readily at 360, the 

 boiling-point of mercury. In order to see if a lower temperature would suffice, the 

 following experiment was performed : In the horizontal part of a long tube, bent at 

 right angles, a small quantity of pure amorphous phosphorus was placed. The vertical 

 part of the tube was open, and dipped into a trough of mercury. After the tube had 

 been filled with moist oxygen, the other end which contained the phosphorus was 

 sealed. This end was inserted in the hole in the side of the air bath. The tempera- 

 ture was kept constant, at 260. After ten minutes the mercury had risen 5 centi- 



MDCCCLXXXVIII. A. 4 P 



