April 3, 1890] 



^m THE GLOW OF PHOSPHORUS} 



^^hUE -woxA phosphorus, originally applied to any substance, 

 solid or liquid, which had the property of shining in the 

 dark, has gradually lost its generic sense, and is nowadays 

 practically restricted, as a designation, to the wax-like inflam- 

 mable substance which plays such an important part in the com- 

 position of an ordinary lucifer match. Phosphorus, indeed, is one 

 of the most remarkable of the many remarkable substances 

 known to the chemist. The curious method of its discovery, 

 the universality of its distribution, its intimate connection with 

 ihe phenomena of animal and vegetable life, its extraordinary 

 physical properties and chemical activity, its abnormal mole- 

 cular constitution, the Protean ease of its allotropic trans- 

 formations — all combine to make up a history which abundantly 

 justifies its old appellation of phosphorus mirabilis. Godfrey 

 Ilankewitz more than 150 years ago wrote : " This phosphorus 

 is a subject that occupies much the thoughts and fancies of some 

 alchymists who work on microcosmical substances, and out of it 

 they promise themselves golden mountains." Certainly no man 

 of his time made more in the way of gold out of phosphorus 

 than Mr. Hankewiiz, for at his Utile shop in the Strand he en- 

 joyed for many years the monopoly of its sale, guarding his 

 Arcana with all the jealousy of a modern manufacturer of the 

 element. 



Phosphorus, or, as it was then called, the noctiluca, was first 

 .seen in this country in 1677. It was shown to Robert Hoyle, 

 who had already worked on phosphorescence in general, and who 

 seems to have been specially struck with the remarkable pecu- 

 liarity of a faciitious body which could be made " to shine in 

 the dark without having been befo e illumined by any lucid 

 substance and without being hot as to sense." Tn these respects 

 the substance differed from all the phosphori hitherto known. 

 The conditions which determine its glow were the subject of the 

 Earliest observations on phosphorus, and Boyle has left us a 

 minute account of his work on the point. In the first place, he 

 noticed that the substance was only luminous in presence of air. 

 He accurately describes the nature of the light, and noticed that 

 the water in which the phosphorus was partially immersed ac- 

 quired "a strong and penetrant ta^le, . . . and relished 

 a little like vitriol." On evaporation it would not "shoot into 

 crystals, . . . but coagulated into a substance like a Gelly, or 

 the Whites of Eggs which would be easily melted by heat." On 

 heating this " Gelly " it gave off " flashes of fire and 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. " .\ giain of the noctiluca dissolved in 

 Alkohol of Wine and shaken in Water ; it render'd 4CO,oco times 

 its weight luminous throughout. And at another Tryal 1 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 wr.s that when it had been a 

 long time exposed to the air it emitted strong and odorous Exhala- 

 tions 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. 

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

 actually the earliest account of what is one of the most para- 

 doxical phenomena connected with the luminosity of phosphorus, 

 namely its increase on rartfying the air. "It being now gener- 

 ally 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 eflect this, I placed a considerable lump of this matter (phos- 

 phorus) 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 foin.er dulness." This observation was 

 repeated and its result confirmed by Hawksbee in this country 



Lecture detivered on Friday evming. March 14, at the Royal lastitu- 

 tn. 11, by Prof. Thorpe, F.R.S. 



NATURE 



523 



and by Homberg in France, and seems subsequently to have letl* 

 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 phos- 

 phorus would not glow in the Torricellian vacuum ; and Lavoisier, 

 in 1777, showed that it would not infianoe under the same con- 

 ditions ; and. the subsequent experiments of Schiotter, Meissner, 

 and M tiller are decisive on the point that the glow is the con- 

 comitant of a chemical process dependent upon the presence of 

 oxygen.. It is, however, remarkable that phosphf rus will not 

 glow in oxygen at the ordinary atmospheric piessure and tem- 

 perature, bur that if the oxygen be rarefied the glow at or.cebejiins, 

 but ceases again immediately the oxygen is compressed, Indeer'^. 

 phosphorus will not glow in compressed air, and the flame ot 

 feebly burning phosphorus may be extinguished by suddenly in- 

 creasing the pressure of the gas. Phosphorus, however, can l;e 

 made to glow in oxygen at the ordinary pressure or in compressed 

 air if the gases be gently warmed. In the case of oxygen tl^e 

 glow begins at 25° and becomes very bright at 36''. In com- 

 . pressed air the temperature at which the glow is initiated depend.s 

 upon the tension. If the oxygen be absolutely deprived of 

 moisture the phosphorus refuses to glow under any conditions. 

 This fact, strarge as it may seem, is not without analogy ; the pre- 

 sence 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 extingui hed iheglow of phosphonis. 

 The late Prof. Graham confirmed and extended these ol:>serva- 

 tions ; he showed that relatively small quantities of olefiant ;;ns 

 and of the vnpours of ether, naphtha, and oil of turpentine 

 entirely jirevented the glow ; and subsequent observers have 

 found that many essential oils, such as those of peppermint at^d 

 lemon and the vapours of camphor and asafcetida, even when- 

 present in very small quantity, stopthe absorption of oxygen anck 

 the slow combustion of phosphorus in air. 



It has been established that whenever phosphorus glows ii> 

 air or in rarefied oxygen, ozone 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 pro- 

 cess of which the glow is the visible sign. That there is some 

 intimate connection between the luminosity of the phosphorus- 

 and the production of these bodies is highly probable. Schiin- 

 bein, as far back as 1848, sought to demonstrate 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- 

 perature, 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 2^", at which tempera- 

 ture phosphorus glows brightly. On the assumption that the 

 oxidation of the phophorus 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, + 

 O" -f 

 O -f 



H.,0 



P.P5 + O. 

 O3. 



HoO.,. 



Both these reactions may, of course, go on simultaneously ; 

 ozone and hydrogen peroxide are not inmually inct-mpatihle; 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 combina- 

 tion 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 rarefying the atmosphere in which 

 it is placed its volatilization is increased, which serves to account 

 for the increased glow when the pressure of the gas is diminished. 

 When phosphorus is placed in an atmosphere of hydrogen, 

 nitrogei', or carbonic acid, these gases, when brought into con- 

 tact with oxygen, become luminous from the oxidation of the 

 vapour of phos^phorus diffused through them. The rapidity of 

 volatilization varies with the particular gas ; it is greatest in the 

 case of hydiogen, and least in that of carbonic acid. Indeed,, 

 a stream of hydrogen gas at ordinary temperatures carries away 

 comparatively large cpiantities of phosphorus, which may be 

 collected by appropriate solvents. No ozone and no glow is. 



