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tilling it per fc in a retort, with a heat graduallyincreafed to rednefs. A very fmall portion ofthe filver however remains in the white powder,which may be recovered by fublimatien, inwhich the fub-muriat of mercury riles pure, anda grey powder remains, which melted withborax gives a fmall globule of filver. In thisway lVlarggraf recovered almoft the whole ofhall an ounce of line filver which was firftconverted into luna cornea, for the amalgamleft after diltillation half an ounce of filverwanting four grains, and the fmall globuleprocured from the mercurial fublimate weighed■i\ or 3 grains more. He alfo obferves thatit is quite necefiary to wafh out the mercurialniuriat from the amalgam before the latter isdiddled, for if it is,left in, the affinities arechanged at a high temperature, and luna corneaand running mercury are again formed.

The fame reduftion of luna cornea takesplace without the labour of rubbing, by puttingit along with the carbonated ammonia andmercury in a retort, adding a good quantityof water, and diddling to drynefs. Thereremains then in the retort the amalgam andfub-muriat of mercury, which are to be treatedas above. The ammoniacal liquor which comesover may be faved for a future operation.

In all tliefe procefles it is always to beremembered that it is the carbonated and not thecauflic ammonia which is to be employed, forcauftic volatile alkali can never be heated withmuriat of mercury without danger of producingthe very formidable fulminating powder, whichwill be prefently deferibed.

Muriat of filver may alfo be reduced by fufionwith lead. Kunckel recommends mixing themuriat with thrice its weight of granulated leadand melting the mixture in a retort. It thenwill contain two diftintt fubdances, the upper ismuriat of lead, and the lower metallic filver,alloyed however with a good deal of lead,which mud afterwards be feparated by cupella-tion. Proud obferves in this procefs that twoparts of lead are quite fufficient, but there isalways fome lofs of the filver after cupellation,as it never exceeds about 74 parts from 100 ofthe luna cornea. Several other of the metalswill anfwer the purpofe of die lead, but with-■ out the fame advantages.

The habitudes of muriat of filver with ironand its falts are important. If the muriat isboiled in an iron vefTel with water, and fomebits or filings of iron, a powder graduallyeolle&s at the bottom, which is metallic filver,

and when heated with borax, melts into a purebutton of metal. The water contains muriat ofiron. The decompofition is known to be corn-pleat when the powder of filver is not blackenedby expofure to the fun. This procefs which isgiven by Sage, was repeated by Proud with thefollowing reiults. A hundred parts of dry lunacornea (containing 75 j per cent, of filver,, weremixed with as much iron filings, and boiledwith water for fome time in a filver veflel. Thepowder remaining was then well wafhed andmixed with mercury to colleft the filver. Thisamalgam left after diltillation 72f parts of filver,and on adding more mercury to the powder2 } more of filver were left, making in all 75per cent. Zinc filings will anfwer as wellas iren.

Luna cornea is not decompofed by fulphat ofiron, but it is reduced by iron in the a£t of di-lution in dilute fulphuric acid, when in contaftwith it. Muriatic acid and iron have the fameeffect. We may here alfo make a few obferva-tions on the mutual action of fulphat of ironand metallic filver. d

When the red fulphat of iron (or that inwhich the metal is fully oxygenated) is boiledwith pieces of filver, a portion of the metal isdilTolved fo as to give a luna cornea with fait,and the fulphat is reduced to the ftate of thegreen, or fub-oxygenated, fulphat. But onkeeping the folutions together for a time brightfeales of metallic filver form in them (probablywith the affiftance of the light) and the fulphatreturns to its original ftate of compleat oxyge-nation. On the other hand a cold folution ofthe green fulphat mixed with fulphat of filver,decompofes the latter and metallic filver preci-pitates. Hence it appears that at a commontemperature the green fulphat takes oxygen fromthe falts and oxyds of filver, but when the heatis raifed the reverfe takes place, and the redfulphat yields oxygen to filver. In the lattercafe however the affinity of the oxyd of filver forfulphuric acid muft affift in the decompofition.

Muriat of filver is liable to be formed when-ever filver remains for a length of time in con-tact with any muriatic fait. Thus Prouftfound filver dollars deeply corroded and partlyconverted into muriat, by lying for many monthsat the bottom of the fea on the coaft of Spain .

The acetous acid has no action whateverupon pure filver, but it combines eafily withits oxyd. Acetite of filver is readily formed byadding acetite of potafh to nitrat of filver, ormore fimply by boiling this acid on the carbon-

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