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smuriatic acid gave out no gas, becaufe therewas no power applied capable of refolving thefugar into hydrogen. Many other methods of.obtaining the gas might be fuggefted, in whichfulphur ihould be in contadt .with hydrogen atthe moment of its formation. This gas howeveris not produced by heating fulphur in contactwith hydrogen gas, nor by pafl'mg this gas overfulphur melted, and kept red-hot in a clofetube, fo that it appears neceffary in all cafesthat the hydrogen Ihould be prefented to thefulphur either in a nafcent Hate, or coudenfedin a folid or liquid.

According to Mr. Kirwan, 100 cubic inchesof this gas contain about 30 grs. -of fulphur.Whence, fuppofing that 100 cubic inches ofcommon air weigh 30.414 grs. (at 6o° Th. and29.5 0 Bar.) and that this gas is heavier thancommon air in the proportion of 10000 to 9038.,

100 cubic inches of fulphuretted hydrogenfliould weigh 33.65 grains, of which 30 grainsare fulphur, and 3.65 grains hydrogen. Thequantity of fulphuretted hydrogen contained inany water, he eftimates by the quantity of ful-phur precipitated and collected, when a givenportion of the water is decompofed by nitrousgas and common air, as will be more fullydefcribed under the article Waters [Mineral),In this method therefore, and from the abovedata, 30 grs. of fulphur would indicate loocubic inches of the gas, and therefore onegrain of fulphur is equivalent to 3 k cubic inchesof the gas.

The eftimation made by Thenard, of thecompofxtion of -this gas, does not even approachto that of Kirwan juft mentioned. Thenardeftimates the cubic centimetre of the gas to.weigh (at a medium prelTiire and temperature)1.5 13 millegrammes, which reduced to Englilhmeafure would give the weight of 100 cubicinches at 41.1 grains inftead of 33.65 as Mr.Kirwan eftimates it. Mr. Thenard anaiyfes thegas by caufing water to abforb the whole, andthen adding oxymuriatic acid fufficient hrft toprecipitate the fulphur, and then to convert ittotally into fulphuric acid, from the weight ofwhich (as indicated by the quantity of fulphatof barytes formed on adding muriated barytes )he eftimates that of the fulphur entering intoits compofition. From thefe data he concludesthat 100 parts, by weight, of the gas are com-peted of 70,857 of fulphur, and 29.143 °fhydrogen, whereas the proportions given byMr. Kirwan would be (in too by weight) about89.1 of fulphur, ami i®-9 of hydrogen.

Though much of this difference mull be<afcribed to the different mode of analyfis pur-

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fued, part of it may doubtlefs arife from occa-fional variation in the cor.ftitution of the gas*'for there is no fatisfactory reafon for fuppofingthat the degree of fuiphuration of this gasfhouid be always uniform, any more than theproportion of phofphorus in the phofphurettedhydrogen, or of arfenic, in the arfenicated hy-drogen, which are known to vary confiderably.

There is likewife fome difference in the ful-phuretted hydrogen, according to the fulphuretor other material from which it is procured,independently of any palpable admixture of car-bonic acid or other known gaffes, for thatwhich is procured from the fulphuret of ftron-tian burns with a red colour like the falts of thisearth, which would {hew that fome of theflrontian itfelf is volatilized along with the gas-

Metallic Hydro-fulphurets .

Sulphuretted hydrogen exercifes a veryftrong adtion on fome metals in fubftance, andon many more metallic falts. When fulphu-retted hydrogen, either in the galfeous form, ordiffolved in water, is added to a metallic folu-tion, part of the hydrogen firft unites with partif not all of the oxygen of the metallic oxyd,and reduces it nearly to the metallic ftate, andthe remainder of the fulphur and hydrogenunite with the metal, and the whole is generallyfeparated from the acid of the folution in theform of a coloured precipitate, which thereforeis either a fulphuret or a hydro-fulphuret ofthe metal according to circumftances. Some-times too a fmall portion of fulphuric acid isformed at the fame time, which renders theplay of affinities ftill more complex. Some ofthe metallic folutions afford no precipitate withfulphuretted hydrogen, or at leaft the precipi-tate is rediflolved by a flight exccfs of acid, butwith other metals it is permanent.

Nitro-muriat of Gold is precipitated black byhydro-fulphuretted water, 1 * — nitrat of Silver ,black, but the precipitate is again foluble byagitation if there is a feniible excefs of acid—nitrated Mercury, yellowifh brown, and Cor-rofive Sublimate dark yellow, which becomesblack by agitation—fuljlhat of Copper , black,and nitrat of Copper brown—nitro-muriat ofPlatina , reddilh white—the falts of Lead, deepblack—thofe of Zinc , white—the falts of Bif-muth, reddifh brown, palling into .black—mu-riat of Tin , a duli white .

The metals that are not precipitated fromtheir folutions by iulphuretted hydrogen, areIron, Cobalt , Nickel , Manganefe, and in fomecafes Antimony and Arfenic. Thefe folutionshowever are deeply coloured by the fulphuret,id Beithollct.