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perature. The only difference in. this cafe isthat both gaffes are previoufly faturated withphofphorus, inftead of only one.

When a flick of phofphorus is confined inhydrogen gas no light is produced, but after atime the gas diffolves fome of tire phofphorus,and then, like phofphorized azot, it becomesluminous on the contaft of oxygen or any aircontaining oxygen. In like manner pure hy-drogen added to phofphorized oxygen rendersit luminous, and even at as low a temperatureas 4-4-° according to Spallanzani .

With hydrogen, phofphorus unites in twoftates of faturation, the lowed; is that whichhas been juft mentioned, and is produced bykeeping phofphorus in hydrogen at a moderatetemperature. The other is the gas producedby boiling the phofphorus in an alkaline folution,and will be afterwards deferibed. The formergas is merely luminous by expofure to air oroxygen, the latter takes fire and burns with abright fiafli and flight explofion; the formertherefore may for the prefent be diftinguifliedby the term fub phofphuretted hydregeti, and thelatter phofphuretted hydrogen.

Phofphorus kept in l’ulphuretted hydrogendiffolves therein, but is not luminous. Onadding common air a large blueifh flame isproduced. This luminous gas feems to bemore permanent and condenfed than the others,attaching itfelf to the hands or to the veffel inw'hich the experiment is made, and givingthem a very bright luminous coating, whichremains for feveral minutes.

No very interefting appearance takes placewhen phofphorus is- confined in the other gaffes,but when thrown into the oxymuriatic acid gasit foon takes fire, and burns rapidly andbeautifully.

In all the above experiments where it isafferted that the gas containing the phofphorusremains abfolutely dark, it is underftood thatit is confined by mercury, for when kept overwater, the oxygen which this fluid ufuallycontains may be difengaged, and the minuteftquantity will become fenfible by fuch a delicateteft.

The folution of phofphorus in oxygen gas ata. low temperature is a very curious circum-ftance, for it muft imply a very intimate unionthe two without any approach to combuftion,mce at any time combuftion may be excited ine mixture either by raifmg the heat to 8i°, ory a t ing azotic or hydrogen gas, and fincealter Uie temperature has been raifed to the

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point of luminoufnefs and flow combuttion, and.again reduced, no effefb is then produced bythe above additions.

The fub-phofphuretted hydrogen having beenalready mentioned, we may proceed to describethe phofphuretted hydrogen. This gas wasfirft difeovered by Gengembre, who prepared itby boiling phofphorus in alkali. It is eafdyproduced in the following way: put fome piecesof phofphorus in a very fmall bottle with acurved tube, or in a fmall retort, fill the veflelto the neck with a weak folution of caufticpotafli, and heat it to boiling, taking care todip the open end of the bottle or the tube inwater or mercury to prevent the accefs of air.When the folution begins to boil, bubbles ofgas rife to the furface, which kindle immedi-ately and burn with a bright flafli. within theveflel as long as any oxygen remains. Thiscaufes a rapid abforption, fo that unlefs theveflel is nearly full, much of the water ormercury rufties up, but after a while thisceafes, and the difeharge of gas is copious andregular. It is the peculiar property of this,phofphuretted hydrogen to burn with a veryvivid flafh and a flight fnapping noife the 1moment it comes in contact with the atmo-fphere, and after each bubble has thus exploded,a very remarkable circular ring of white fmokerifes from the flafli, and mounts about two orthree feet in the air, gradually, widening till itdifperfes. This gas if received by bubbles in.a jar of oxygen gas burns with a ftrongerexplofion and a brilliant flafli of flame, perhapsmore beautiful than any other that chemiitry camexhibit. Phofphuretted hydrogen may alfo beproduced by heating phofphorus v,ery. ftrongly,,and fubliming it in an atmofphere of hydrogen.Another method of producing it is Amply by.dropping into water fome phofphuret of lime,,as will be prefently mentioned.

Phofphuretted hydrogen has a ftrong and.unpleafant fmell fomewhat like that of ftalefifli. It is confiderably lighter than common',air, but its compofition feems to vary according;to the circumftances and time of its formation..If kept in the dark, and over mercury, it retains-its inflammability for a length of time, but.in the light it is foon changed, and no longerkindles on admiffion of common air..

When this gas recently prepared is agitated!with cold water, a confiderable quantity isabforbed, and a liquor is formed of a faintyellow colour, a difagreeable fmell and a bitter'and naufeous tafted It is not luminous in the-re Chim. tore. 35.