﻿of Phosphorus, Sulphur, and Aldehyde. 507 



study of the connexion between the velocity of the change 

 and the concentration of the oxygen. For this reason, and 

 at the suggestion of Professor van't Hoff, I took up the study 

 of the velocity of the reaction between phosphorus and oxygen. 



Rate of Oxidation of Phosphorus in Moist Oxygen. 



(a) Behaviour in Air. 



Some measurements have already been recorded by Ikeda*. 

 He found that at 19° the oxidation of phosphorus in moist 

 air takes place with a velocity which is nearly proportional 

 to the concentration of the oxygen. At the lower pressures 

 the reaction went a little faster than is required by exact 

 proportionality. 



My first experiments were made in the same way as those 

 of Ikeda. The apparatus consisted of a bottle of 1^ to 2 litres 

 capacity with two necks, into one of which a test-tube was 

 fitted by means of a cork, while the other communicated with 

 a manometer. The test-tube reached to about the middle of 

 the bottle, and its lower, closed, end was surrounded by a 

 cylinder of phosphorus which was kept cool by a current of 

 water, of the same temperature as the water-bath, which 

 flowed through the test-tube. The whole apparatus stood in 

 a large water-bath the temperature of which was kept con- 

 stant. The experiments were made as follows : — The bottle, 

 containing a little water and air, was placed in the thermostat, 

 connected with the manometer, and allowed to stand until it 

 had assumed the temperature of the bath. The phosphorus 

 cylinder was then quickly placed in position and the pressure 

 read off. Subsequent readings of the pressure made at con- 

 venient intervals furnished the data from which the velocity 

 of the reaction was calculated. The concentration of the 

 oxygen is proportional to its partial pressure so long as the 

 volume remains constant (which w r as the case in the method 

 just described), and the decrease of pressure per minute is 

 proportional to the quantity of oxygen which undergoes 

 change per minute — that is, to the velocity of the reaction. 



The phosphorus was so little acted on during an experiment 

 that its surface remained practically undiminished. 



The numbers obtained in two experiments made in this 

 way are given in the following Table (I.). They agree with 

 those obtained by Ikeda in showing that the velocity of the 

 reaction (in moist air) diminishes a little more slowly than 

 the partial pressure of the oxygen. This is seen in the 

 increase in the values of K/ (column 4) . These numbers are 



* Journ. Coll. Science, Imperial University, Japan, vi. p. 43 (1893). 

 2 M2 



