74 Professor T. E, Thorpe [Marcli 14, 



of tLo gas. Phosphorus, however, can be made to glow in oxygen 

 at the ordinary pressure, or in compressed air, if the gases are gently 

 warmed. In the case of oxygen the glow begins at 25°, and becomes 

 very bright at 36°. In compressed air the temperature at which the 

 glow is initiated depends upon the tension. If the oxygen is abso- 

 lutely deprived of moisture, the phosphorus refuses to glow under 

 any conditions. This fact, strange as it may seem, is not without 

 analogy ; the presence of traces of moisture appears to be necessary 

 for the initiation or continuance of chemical combination in a number 

 of instances. 



It was observed by Boyle that a minute quantity of the vapour of 

 a number of essential oils extinguished the glow of phosphorus. The 

 late Professor Graham confirmed and extended these observations ; 

 he showed tliat relatively small quantities of olefiant gas, and of the 

 vapours of ether, naphtha, and oil of turpentine entirely prevented tlie 

 glow, and subsequent observers have found that many essential oils, 

 such as those of peppermint and lemon, and the vapours of camphor 

 and asafoetida, even when present in very small quantity, stop the 

 absorption of oxygen and the slow combusti(m of phosphorus in air. 



It has been established that whenever phosphorus glows in air, 

 or in rarefied oxygen, oz(me and hydrogen peroxide are formed, but 

 it is not definitely known whether the formation of these substances 

 is the cause or the effect of the chemical process of which the glow is 

 the visible sian. That there is some intimate connection between the 

 luminosity of the phosphorus and the production of these bodies is 

 highly probable. Schonbein, as far back as 1848, sought to demon- 

 strate that the glow depends on the presence of ozone. It is certainly 

 true that many of the substances, such as the essential oils, which 

 prevent the glow of phosphorus, also destroy ozone. At a low tem- 

 jDcrature phosphorus produces no ozone in contact with air, neither 

 does it glow. It has been found, in fact, that with air ozone is 

 produced in largest quantity at 25°, at which temperature phosphorus 

 glows brightly. On the assumption that the oxidation of the phos- 

 phorus consists in the immediate formation of the highest oxide, the 

 production of the ozone and the hydrogen peroxide has been represented 

 by the following equations : — 



p,-}-0, = PA + 



0+02 = 03 



O +HoO = HA- 



Poth these reactions may, of course, go on simultaneously, as ozone 

 and hydrogen peroxide are not mutually incompatible ; the synthesis 

 of hydrogen peroxide by the direct oxidation of water seems to occur 

 in a number of processes. But such symbolic expressions can at 

 most be only very partial representations of what actually occurs. 

 It is highly probable that the combination which gives rise to the 

 glow only occurs between the vapour of phosphorus and the oxygen. 

 Phosphorus is sensibly volatile at ordinary temperatures, and by 



