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fulphat of mercury, which, fublimed with 30oz. of dried muriat of foda, yield 20 oz. of cor-rofive muriat.

Corrofive muriat may be prepared withoutfublimation : the ufe of this latter procefs beingonly to feparate the fait from the other mate-rials which are not volatile at a low red heat.T he following way is given by Von Schmidt: pdilTolve 2 ounces of mercury in 3I oz. (a lefsquantity would be fufficient) of fulphuric acid,and diftil to drynefs in the ufual way. Add tothe white fulphat of mercury in the retort afolution of 54 oz. of common fait, and boil themixture for an hour, then filter the liquor whilehot, and evaporate it to drynefs. Add to therefiduum (which now confifts of fulphat offoda, corrofive muriat, and perhaps fome unde-compofed common fait) about 16 oz. of alcohol, *digeft for an hour in a moderate warmth, and■decant off the clear liquid. This is a folutionof the corrofive muriat in the alcohol, the otherfalts being infoluble in the fpirit, and thereforeremaining at the bottom. Then evaporate thealcoholic folution to drynefs, which leaves thecorrofive muriat as a perfeftly white mafs whichmay be obtained in beautiful cryftals by fubfe-quent diffolution in boiling water and cooling.To extract all the mercurial muriat from the mafsit will be advifeable to repeat the procefs withabout 8 oz. more of alcohol, and proceed asbefore.

Corrofive muriat may alfo be made by directfolution and cryftallization. If oxyd of mercuryis mixed with water in a Woulfe’s bottle, and acurrent of oxymuriatic acid gas be paffed throughfor fome time, a folution is formed, which givesby evaporation cryftals of very pure corrofivemuriat. In this manner the fait may be ob-tained of perfect purity.

The fame product is formed when oxymuri-atic acid is added to the nitrat of mercury eitherfoluble or infoluble in water; by evaporation the nitric acid flies off, together with theexccfs of oxymuriatic acid, and the corrofivemuriat is obtained in very pure and regularcryftals.

But if oxymuriatic acid be poured on runningmercury it firft reduces it to a grey powderwithout extrication of any gas, which powderis the fame in nature as the mild muriat orcalomel to be prefently defcribed. But if anexcefs of the acid be fo ufed this grey powderis diffolved, and the folution is changed to cor-rofive muriat.

Corrofive muriat, jn whatever way it be

1 Van. Mons Journ. or Phil. Mag, Vol. xvi.V ' Ann.

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formed, is a fait which cryltallizes, when formedby fublimation, generally in long needles, butby watery folution it a fleets the form of four-. fided prii'ms. Its tafte is extremely acrid, nau-feous, and ftrongly metallic, and fo permanentthat it is very difficult to get it off the palate..It is not ddiquefcent. Cold water difiolvesft to ~ of its weight of this fait, but boilingwater much more. When heated moderately(but to a degree much above that of boilingwater) it fublimes in the form of a denfe whitefmoke moft exceffively prejudicial to thofe thatrefpire it. Light has a powerful effeft on thisfait. If it is expofed to a ftrong light it after awhile becomes mealy on the furface, and ifthen thrown into boiling water the whole willnot dilTolve as at firft, but a refidue of a dingywhite colour fettles to the bottom which isfound to be calomel. Alfo when a clear folu-tion of the fait is expofed to the fun’s rays afimilar. precipitation of a white infoluble fub-muriat takes place. Hence all folutions of thisfait becomes muddy by keeping unlefs fccludedfrom the light. M. Boulley q found that duringthis change oxygen was given out.

This fait is alfo foluble in alcohol, whichwhen moderately warm takes up about -J of itsweight/ Boiling alcohol difiolves nearly itsown weight, moft of which feparates again oncooling.

Sulphuric acid s does not decompofe this fait,but being poured on it, reduces it to a powder,limply owing to the abftrarition of its water ofcryftallization; for on adding water the powderis entirely rediffolved. Nitrous acid added tothis fait difiolves it when heated and lets it goon cooling, unaltered. The muriatic acid dif-folves this fait, but renders it lefs eafily cryftal-lizablew

All the alkalies and alkaline earths decom-pofe corrofive fublimate. The fixed alkalies andalkaline earths when cauftic give a precipitate,at firft: orange, which afterwards deepens into abrick red. But the carbonated alkalies produce aprecipitate of a much lighter {hade of colour.Corrofive muriat and alkalies therefore aremutually a tell for each other, and are oftenufed as fuch.

The action of ammonia on this fait is Angu-lar. With the other folutions of mercury am-monia gives a black powder, which is the metalalmoft reduced to a metallic ftate, as alreadymentioned, but when this alkali is added to afolution of corrofive muriat a copious white pre-cipitate falls down, which remains white after

de Chem. tom. IxiV. ' Effays Vol. iii. ‘ Bergman.

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