P H O

P H O

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this folution is fmeared over the face or hands,the warmth of the body caufes the oil toevaporate fpeedily, after which the thin in-fenlible pellicle of phofphorus that remainsbecomes ftrongly and uniformly luminous, andcontinues fo for fome time. This amufingexperiment is no ways hazardous, as the quan-tity of phofphorus left on the Ikin is too fmallto do mifchief.

Phofphorus may be equally well diffolved inthe fixed oils. Oil of olives or almonds arethe moll convenient. Heat the oil in anyveffel with the phofphorus for about a quarterof an hour, and the oil will diffolve enough ofthe phofphorus to be extremely luminous whenfmeared over the Ikin or any warm furface.

Sulphuric ether difi'olves phofphorus, butthis folution is not of itfelf luminous. Alcoholadded to it makes it milky.

The habitudes of phofphorus with the diffe-rent gaffes offer feveral very interefting pheno-mena. Thefe have been examined with greatcare by Fourcroy, Vauquelin/ Spallanzani, *Brugnatelli, 1 * and others, with the particularview of refuting fome obl'ervations of Goettlingon the luminoufnefs of phofphorus in azoticgas, which were fuppofed to militate againftthe modern theory of combuftion.

When a flick of pure phofphorus is in-troduced into very pure oxygen gas, no lightwhatever is perceived, though the experimentbe made in perfe£t darknefs, at any temperaturebelow 8o° or 8i“. But if it be raifed to thispoint by putting the warm hands on the outfideof the jar, the phofphorus becomes very lumi-nous, and is furrounded with white vapours.This appearance continues till the temperatureis reduced to 55°, when it ceafes entirely.This luminoufnefs is caufed by a low combuftionof the phofphorus and confequent generationof phofphoreous acid, fo that in this, as inall the fubfequent experiments, whenever theluminous appearance has taken place litmuspaper within the jar will be reddened. From8l° to 104° this flow combuftion continuesbut with increafing rapidity, but at about 104*the phofphorus, which is then melted, takesfire and burns rapidly with intenfe heat andflame as already defcribed. But though phof-phorus does not begin to be luminous, andtherefore to undergo combuftion in pure oxygenat a lower temperature than 8i°, it impercep-tibly diffolves therein at the heat of 55°, andperhaps lower, as will be prefently fhewn.

Phofphorus introduced into perfectly pursazotic gas, (fuch as that extracted from muf-cular flefh by weak nitric acid) is not luminousat any temperature, but may be melted andeven fublimed therein without fhewing the leaitlight, or undergoing the fmalleft combuftion.It diffolves in it however at 55° and enlargesits bulk about T V according to Berthollet , ashas been mentioned under the article Eudio-metry, [which fee). But if a Angle bubble ofoxygen gas, pure or impure, be thrown upinto a jar of this phofphorized azot, a prettyftrong blue light is perceived at the moment ofcontaCl which continues for a fliort time. Thefame effeCt, but in a much greater degree, isproduced by inverting the experiment, andadding bubbles of phofphorized azot to oxygengas, in which cafe the whole veflel is filledwith a fine lambent blue flame. Not only pureoxygen, but common air or any other mixtureof oxygen will render phofphorized azot ftrong-ly luminous. It has been mentioned thatphofphorized oxygen gas does not of itfelfbecome luminous till heated to 8i°, but (whatappears at firft very remarkable) if a jar befilled with it and kept at the temperature of 55°and a few bubbles of azot be thrown up, thewhole jar immediately fhines with a bright bluelight like that of the eleftric aura. It appearstherefore that when phofphorus, azot, andoxvgen are prefent, the phofphorus firft com-bines with the azot, and being thus extremelydivided, it is able to undergo combuftion withoxygen at a much lower temperature thanwhere the azot is abfent. This is exactly whattakes place when phofphorus is confined at amoderate temperature in atmofpherical air, andhence to employ phofphorus as an eudiometerat this heat the prefence of the azot is neceffaryto fet in action the combuftion.

Meffrs. Fourcroy and Vauquelin found thatwhen phofphorized oxygen had been firft madeluminous by railing the heat to 81°, and thencooled to 55'’ and mixed with azot, no lightcould be perceived.

The fame chemifts alfo obferve that whenphofphorized oxygen and phofphorized azot(both made by keeping phofphorus in therefpective gaffes at a low temperature for fomehours) are mixed together at 55°, no light isperceived, which is a very Angular faff, andappears to contradict the experiment in whichazot renders phofphorized oxygen luminous, oroxygen, phofphorized azot, at the fame tem-

« Ac. CJiiro, tom, Zi,

* Do, torn. %%.

1 Do, tom 34,