The elements of materia medica and therapeutics . iousand cold receiver, it falls in a most impalpable and perfectly whitepowder, which requires only one elutriation to fit it for use; itthen remains perfectly colourless. By a modification of the process,it may be suffered, as it sublimes, to fall into water, according toMr. JeueHs ])atent. The above circumstances, too, account for the various appear-ances mider which calomel occasionally presents itself in commerce : it may be added, that^«- J^- the bufi aspect of this substance indicates theabsence of coiTosive sub-limate ; though it by nome
The elements of materia medica and therapeutics . iousand cold receiver, it falls in a most impalpable and perfectly whitepowder, which requires only one elutriation to fit it for use; itthen remains perfectly colourless. By a modification of the process,it may be suffered, as it sublimes, to fall into water, according toMr. JeueHs ])atent. The above circumstances, too, account for the various appear-ances mider which calomel occasionally presents itself in commerce : it may be added, that^«- J^- the bufi aspect of this substance indicates theabsence of coiTosive sub-limate ; though it by nomeans follows as a con-sequence that whensnow-white it containsit. AVhen the surfaceof massive sublimed ca-lomel is scratched, italways exhibits a buffcolour : it also becomesyellow when heated, butloses its tint as it againcools. Mr. Jewells process*for preparing calomelconsists in keeping thereceiving vessel filledwith steam, so that the vaporous calomel is condensed in it, andtakes the form of a fine powder, which is much finer than can be ob-. Henrys modification of Jewells apparatus for pre-paring calomel by steam (Hydrosublimate ofmercury). a. Furnace, containing an earthen retort (having^ a wide and short neck), in which the ingredients for making calomelare placed. b. An earthen receiver, having three tubulures : one communi- cating with the retort; a second dipping into water in anearthen jar, and a third connected to a steam-pipe. c. steam-boiler. Brooke, AnvaU of of fheniistry, 4th eu. p. 7SReport, of Arts, xiii. 79, 2d Series. CHLORIDE OF MERCURY, 739 tained by levigation and elutriation. This process has been improvedbyM. 0. Henry (fig. 119). The Dublin College directs Precipitated Calomel {Calomelasprceci-pifaium, D.) to be thus prepared :— Take of purified Mercury, seventeen parts ; diluted Nitric acid, fifteen parts. Onthe mercury passed into a glass vessel, pour the acid, and when the mixture shallhave ceased to elFervesce, digest with a medi
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