1890.] on the Glow of Phosphorus. 73 



aucl light " and had a " garlick smell." He also found that the noctiluca 

 was soluble in certain oils, and he particularly mentions oil of cloves 

 as a convenient means of showing the luminosity, as it is " rendered 

 more acceptable to the standers-by by its grateful smell." " In Oyl of 

 Mace it did not appear luminous nor in Oyl of Aniseeds." Boyle 

 describes a number of experiments showing how small a quantity of 

 the phosphorus is required to produce a luminous effect. " A grain 

 of the noctiluca dissolved in Alcohol of Wine and shaken in Water ; 

 it render'd 400,000 times its weight luminous throughout. And at 

 another Tryal I found that it impregnated 500,000 times its weight; 

 which was more than one part of Cochineel could communicate its 

 colour to." " And one thing further observable was that when it had 

 been a long time exposed to the air it emitted strong and odorous 

 exhalations distinct from the visible Fumes." The strong and odorous 

 exhalations we now know to be ozone. 



The earlier volumes of the 'Philosophical Transactions' contain 

 several papers on the luminosity of phosphorus, and one by Dr. 

 Frederick Slare is noteworthy as giving one of the earliest, if not 

 actually the earliest, account of what is one of the most paradoxical 

 phenomena connected with the luminosity of phosphorus, namely, its 

 increase on rarefying the air. *' It being now generally agreed that 

 the fire and flame [of phosphorus] have their pabulum out of the air, 

 I was willing to try this matter in vacuo. To effect this, I placed a 

 considerable lump of this matter [phosphorus] under a glass, which I 

 fixed to an engine for exhausting the air; then presently working 

 the engine, I found it grow lighter [i. e. more luminous], though a 

 charcoal that was well kindled would be quite extinguished at the 

 first exhaustion ; and upon the third or fourth draught, which very 

 well exhausted the glass, it much increased its light, and continued 

 so to shine with its increased light for a long time ; on re-admitting 

 the air, it returns again to its former dulness." This observation was 

 repeated, and its result confirmed by Hawksbee in this country, and 

 by Homberg in France, and seems subsequently to have led Berzelius 

 and after him Marchand, to the conclusion that the luminosity of 

 phosphorus was altogether independent of the air (i. e. the oxygen), but 

 was solely due to the volatility of the body. Many facts, however, 

 combine to show that the air (oxygen) is necessary to the phenomenon. 

 Lampadius found that phosphorus would not glow in the Torricellian 

 vacuum, and Lavoisier, in 1777, showed that it would not inflame 

 under the same conditions; and the subsequent experiments of 

 Schrotter, Meissner, and Miiller are decisive on the point that the glow 

 is the concomitant of a chemical process dependent upon the presence 

 of oxygen. It is, however, remarkable that phosphorus will not glow 

 in oxygen at the ordinary atmospheric pressure and temperature, but 

 that if the oxygen be rarefied the glow at once begins, but ceases 

 again the moment the oxygen is compressed. Indeed, phosphorus 

 will not glow in compressed air, and the flame of feebly-burning 

 phosphorus may be extinguished by suddenly increasing the pressure 



