MR. H. HRKRETON Ii AKKR ON COMBUSTION IN DRIED OXYGKN. 



metres in tlie tube. The combustion went on gradually, diminishing slowly in rapidity, 

 and was complete in four hours. The presence of the phosphorus pentoxide produced 

 tends to dry the ga.s, which would, I think, account for the diminution in the rate of 

 combustion. 



A similar experiment was made with moist oxygen at a temperature of 70. No 

 diminution in volume of the oxygen was noticed, though the tube was heated for 

 three days continuously. 



The temperature of the bath was raised to 100, and kept constant for twenty- 

 three days. During this long heating the combustion was proceeding very gradually, 

 and at the end of the lime half the oxygen was used up. The combustion of amor- 

 phous phosphorus, therefore, at 100 is very slow. 



To show the difference which dryness makes in the rate of combustion, two similar 

 tubes were heated to 100 in the same air bath. One contained phosphorus in oxygen 

 which had been previously dried by a plug of phosphorus pentoxide for three days. 

 The oxygen in the other was kept saturated with moisture by a drop of water floating 

 on the mercury within the tube. After being heated to 100 for seven days both 

 tubes were examined. In the dry tube the mercury had risen 8 mm. ; in the wet 

 tube it had risen 150 mm. 



They were heated another seven days. The combustion in the wet tube was 

 complete ; in the dry tube the mercury had only risen 2 mm. In the former experi- 

 ments, therefore, the phosphorus pentoxide produced does diminish the rate of 

 combustion. 



The luminosity of phosphorus is extinguished if a trace of turpentine vapour be 

 present. A drop of turpentine was allowed to float on the surface of the mercury in 

 a tube containing amorphous phosphorus in moist oxygen. It was heated to 100 as 

 before. The combustion was perceptibly slower than before, though the oxygen was 

 kept saturated with moisture. It went on gradually, however, until after seven days 

 the mercury had risen 100 mm. 



Amorphous phosphorus, as has been stated by many observers, undergoes an 

 extremely slow combustion when allowed to stand in air. After having been kept for 

 a year in a stoppered tube, a specimen of the pure substance was found to be quite 

 moist, and, when it was washed with pure water, the washings gave the reactions of 

 phosphoric acid. 



The Conversion of Amorphoiis Phosphorus into Yellow Phosphorus. 



In one experiment on the combustion of amorphous phosphorus in oxygen, I wished 

 to be quite sure that the temperature to which the wet and dry tubes were heated 

 was the same. Two such tubes were prepared, bent in the middle at a right angle. 

 The phosphorus pentoxide in the dry tube was placed in one arm of the bent tube, the 

 phosphorus being in the other. The ends of the two tubes containing the phosphorus 



