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if the heat was moderate the corrofive muriatrofe in the veffel unaltered, but at a low redheat, calomel was produced. Now as the redoxyd parts with its oxygen at this heat, theremaining mercury mull: have been reduced tothe metallic ftate, and thus by combining withthe corrofive muriat produced the calomel.
The precipitate from nitrat of mercury bypotalh or foda gives no calomel when combinedwith corrofive muriat and fublimed at a mode-rate heat, as Cornette has obferved: p but whenthe precipitate from nitrated mercury by ammoniais ufed, a large quantity of perfeft calomel isprocured.
This experiment, Cornette very fatisfaftorilyexplains by Ihewing the different nature of theprecipitate by ammonia from thofe by the fixedalkalies, and the property of the volatile alkalito reduce metallic oxyds to their reguline ftate.
The deoxydating power of muriat of tin{hews in a fatisfa&ory way the refpeftivecompofition of corrofive muriat and calomel.
Muriat of tin (as will be mentioned underthat article) when faturated with metal has thepower of depriving mercurial folutions of theiroxygen and reducing them to the metallicftate.
When a few drops of muriat of tins are addedto a folution of corrofive muriat, a whitilhyellow powder is obtained which agrees inevery property with calomel; if a little more ofthe tin is added, the powder becomes grey,and on examination by the microfcope isfound to be globules of running mercury. Butif a large quantity of muriat of tin is added atonce to the corrofive muriat, the intermediateftate of calomel is not produced, and the mer-cury at once affumes the reguline form.
When nitrous acid is added to calomel, acopious difengagement of nitrous fumes takesplace, (which does not happen with the perfectoxyds of mercury) the calomel is diffolved, andthe folution diftilled to drynefs gives a whitefaline mafs. This, heated in a clofe vefl’elgives about half its weight of a cryftallized faitwhich fublimes at the upper part of the veffeland is corrofive muriat. The remainder whenfurther heated, emits abundant red fumes,changes colour, and at laft is converted into thered oxyd of mercury.
It has been fuppofed by fome chemifts ofeminence, that the acid of corrofive fublimatewas the oxy-muriatic, or in other words, thatt Mem.de 1 ’Acad. for 1786.
' Phil. Tran
a part of the oxygen which is contained in thi*fait is united to the acid and not to the mercury.As long as they are actually in combination itis not eafy (if at all poffible) to make thisdiftindHon, but it is certain that whenever theacid is feparated from the fait it appears in theform of the fimple muriatic, and not the oxy-muriatic. Mr. Chenevix’s experiments 1, on thishead are decifive, as will be further mentionedunder the article Oxymuriatic Acid. Whenthe fulphuvic acid is added to corrofive muriat,-no acid fumes are difengaged, whereas if theacid were the oxymuriatic, it would probablybe fet at liberty. Likewife when corrofive mu-riat is decompofed by potafti, the refult islimply oxyd of mercury and muriat of potafti,not oxymuriat. Nitrat of filver alfo gives aprecipitate of fimple muriat of filver or lunacornea.
To determine the compofition of corrofivemuriat and of calomel, Mr. Chenevix firftdecompofed 100 grains of corrofive muriat bynitrat of filver to eftimate the muriatic acid,and another 100 grains by potafti for the oxydof mercury, and thus found the conftituents ofcorrofive muriat to be 82 per cent, of oxyd ofmercury, and 18 of muriatic acid. To findout the degree of oxygenation of the metal, an-other portion of mercury was diffolved in nitricacid, to which was added muriatic acid, andthe whole was then evaporated to drynefs, andfublimed. A hundred grains of mercury thustreated gave 143. y of corrofive fublimate, whence(the quantity of acid in this fait being previouflyknown) the refpeftivc quantities of mercuryand oxygen were afeertained, and it appearsthat the metal is here oxydated at the rate of15 of oxygen in 100 of oxyd. Calomel wasthen treated in a fimilar way, being firft dif-folved in nitric acid and decompofed by nitratof filver to determine the quantity of muriaticacid, whence it was found to confift of 88.5 ofoxyd of mercury, and 11.5 of muriatic acid.To find the ftate of oxydation in calomel, agiven portion was boiled with nitro-muriaticacid, evaporated to drynefs, and fublimed, bywhich it was totally converted into corrofivemuriat, and, by comparing thefe data withknown proportions of the corrofive muriat be-fore afeertained, Mr. C. found the metal incalomel to be oxydated at the rate of only 10.7of oxygen in 100 of oxyd, whereas that 0/corrofive muriat is 15 in 100.
s Prouft J. Phys. Tom. 39, p. 337,^
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