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found hi the crucible, which was foft enoughto be cut with the knife, and exactly refembledthe vitreous filver ore. The filver had gained2o grs. or in weight, whence the proportionof fulphur in this artificial fulphuret is about7-7 grains in 100.

A fulphuret, or rather a hydro-fulphuret offilver is alfo formed whenever this metal isexpofed to fulphureous vapours, or any liquidcontaining fulphuretted hydrogen. After acertain time the fubftance of the metal isdeeply fulphuretted, and may be detached inbrittle fcales. But it takes a great length oftime to effect this by mere expofure to fulphu-reous vapours.

The fuperficial tarnifh'wg which filver plate-undergoes when laid by for fome time, ormore fuddenly, when in contact with animalmatters, is probably owing to this change, butit.long remains only fuperficial.

The inftant precipitation of a black hydro-fulphuret in all the falts of filver produced bythe addition of a liquid fulphuret or gafieousfulphuretted hydrogen, has been already men-tioned.

Silver unites with phofphorus though weakly.Pelletier 1 obtained this phofphuret by mixingin a crucible half an ounce of filver in finedivifion, 2 drachms of powdered charcoal, andan ounce of vitrified phofphoric acid, and giv-ing it a full heat for half an hour. On openingthe crucible the fufion was compleat, and oncooling, many luminous jets of phofphoruscame from the filver in the a£t of folidifying.The .filver had gained a drachm in weight, hadloll its du&ility, had a granular and cryftal-lized texture, and was brittle. It remainedwhite, and foft enough to be cut by the knife.When melted on a cupel the whole of thephofphorus burned off, and the filver remainedpure.

Some of the alloys of filver are important.This metal will unite with fome metals per-fectly and without lofing its malleability; withothers it forms a brittle white alloy, but withothers it refufes to unite except in a very minuteproportion.

Silver mixed with gold, dilutes its yellowcolour more or lefs according to its quantity.™Gold with -y'j. of filver is feufibly paler, andthe debafement of colour proceeds pretty uni-formly as the filver is increafed. Thefe mix-tures are very malleable though fomewhatfirmer, harder, and more fonorous than eitherjpetal separately. In this refpeft, as in the

1 Mcmoirci, torn. 1.

colour, a little filver affe&s gold more than alittle gold does filver. On account of the iu-perior price and the alteration of colour, filveris never intentionally alloyed with gold, but alarge portion of the American filver naturallycontains a final) quantity of gold, which re-mains as a fine black flime or fediment whenthe filver is diflblved in aqua fortis.

Homberg mentions in the Memoires del’Acad. des Sciences for 1713 a curious expe-riment to fhew that in certain circum fiances afeparation may take place between thefe twometals. He melted equal parts of gold andfilver in a crucible with a little fea-falt andnitre for a quarter of an hour, and when cold,the gold was found at the bottom in one lump,but retaining about a fixth of filver, and abovewas the remainder of the filver in a feparatebutton quite pure. He obferves that this ex-periment only fucceeds with nearly equalquantities of the two metals, and with a firenot too long continued. If this be accurate,there appears a point of faturation of one me-tal with the other refpedUvriy, but the experi-ment has not been repealed, nor does it agreewith tliofe authors whq affert that the twometals produce an uniform alloy in any pro-portions.

The curious effect produced on filver by be-ing alloyed with platina has been already de-feribed under the article AJfay, p. 118, andthat of Platina .

Copper is the metal ufually employed to al-loy filver in the vaft quantity of this metal ufedfor coin and plate of all kinds. The ftandardfilver of this country is compofed of elevenparts of filver and one of copper. In this pro-portion or even fomewhat more of the alloy,tire mixture remains nearly as white as purefilver, but is much harder, lefs fufible, andthough it remains highly malleable and ductilefo as to bear being extended into any fhape,and wrought in a thoufand different ways, it iscertainly lefs ductile and malleable than a me-tal with lefs alloy, fince fuch a finer metal isrequired to be ul'ed in making filver wire andleaf. On account of the hardnefs given bythe copper alloy it is much better fitted to takea fine impreffion, and is therefore particularlyufeful in coining, and in all domeitic imple-ments.

An alloy of thefe two metals has been ufedin France for coinage for many years, andcalled monnaie de billon, in which the filver isfrom tV to | of the mafs, and which looks like■ .Lewi»'s .Commerce of Am.