M E R

M E R

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feject mercury (being much lefs active in itseffects oil the animal body than the former) and. aifo calomel, by which name it is molt known inmedicine. To avoid confufion we fliall at pre-fent chiefly employ the terms corrofive muriat ,and calomel , in defcribing thefe different falts.

Mercury in the metallic ftate is not a£ted onby the muriatic acid, either hot or cold, butwnen the metal is previoufly oxydated or dif-folved in an acid, the muriatic acid readilyunites with it, and it is in this indirect waythat the muriats of mercury are formed.

Corrofive muriat is prepared almoft exclu-five'iy by the procefs of fublimation. All thematerials neceffary are ; mercury, brought to ahigh degree of oxydation by previous folutionin an acid ; and muriatic acid in a ftate fit to bedifengaged in the vaporous form ; and the heatufed for fubliming expels both the mercury andthe acid in union with each other, which oncooling cryftallize into the corrofive fait.

One good method therefore of making thisfait (which is often ufed) is the following.Diffolve in a glafs veffel ra 8 ounces of mercuryin io or 12 ounces of nitric acid, evaporatethis folution to perfect drynefs, which leaves a•white fait, the nitrat of mercury; rub this faitin a mortar not made of metal with 8 ounces of•decrepitated common fait, and as much fulphatof iron previoufly dried to a white powder byheat. W hen thefe materials are well mixed,put them into a matrafs, of which two-thirdsare left empty, place it on a fand-bath with thehot fand juft hiding the materials, and proceedto fublimation with a heat gradually railed torednefs, allowing the fumes to pafs off up a.chimney, as they would be dangerous to breathe.When cold, break the matrafs carefully (whichis better done if it is previoufly cracked roundV’ith a cold wet iron while Hill hot) and fepa-rate the white cryftallized fublimate from whatremains at the bottom. The former is the cor-rofive muriat, the latter is a mixture of fulphatof foda and oxyd of iron ariling from the mu-tual decompofition of the common fait and thefulphat of iron. The foie ufe of the fulphat ofiron is to afford fulphurie acid, in order to dif-(Gngage the acid of the common fait in a vapo-rous iorm. The corrofive fublimate formed in.-this operation is beautifully cryftallized inneedles if the heat.be moderate, but if it be toogreat, the fait coaiefces into a tingle cake com-?pofed of very linall cryftalljne particles.

In fonte of the large manufaftories of thisfall .in .Holland, the mercury is faid not to be“ Beaims. ® Bergman’s Efiays, vc

previoufly diflbived m nitrous acid but Amplyground to fine powder along wkh the fait anavitriol of iron.

Whenever fulphat of iron is employed, thefublimate is liable to be contaminated with aportion of oxyd of iron, this metal being to thefull as volatilizable by muriatic acid as the oxydof mercury is, but the following fimpie andexcellent procc's firft invented by Kunkel “excludes iron altogether.

Take equal w ights of mercury and fulphurieacid, diftill the mixture to drynefs till only thewhite fulphat of mercury is left, mix this latterfait with about its own weight of common fait,rubbing the mixture well, and then fublime inthe way before mentioned. The fublimate isvery pure corrofive muriat of mercury, and therefidue at the bottom of the veffel is fulphat offoda. The London Pharmacopoeia lias adoptedthis method : the proportions employed are twopounds of mercury, as much fulphurie acid,and three pounds and a half of common fait.In preparing the fulphat of mercury for thisprocefs, the heating of the acid and the mercurymud not be carried fo far as to drive off any ofthe acid which properly belongs to the fulphatof mercury, or in other words, the mixture mudnot be reduced to the ftate of turbith, otherwifethere will be no fulphurie acid left to expel themuriatic acid from the common fait. But ifturbith be employed fome frelh fulphurie acidmull be added.

Another method nearly as economical as theformer, is to grind up mercury, fulphat of iron,common fait, and nitre, and then fublime. Hereboth the nitrous and muriatic acids are driven,from their bafes by the fuperior affinity of thefulphurie, and the mercury, firft diflbived bythe nitrous acid, is afterwards united to themuriatic in the form of corrofive muriat whenfublimed.

A fulphat of mercury fit for giving corrofivemuriat by fublimation with common fait is alfoformed very expeditioully by adding nitratedmercury to a folution of fulphat of potafh, whena white fait, the lub-fulphat of mercury, isprecipitated, being very little foluble, and theclear liquor confifts chiefly of nitrat of potalhformed by double affinity.

With regard to the actual quantity of fub-limate produced from a given proportion ofmaterials, it has been found by an eminentpractical chemiil 0 that 16 ounces of mercurywith 15 ounces of ftrong fulphurie acid (whichis fuificient) will yield about 231 ounces of dry

1. iii, * Original communication.