438 Preparations and Compositions. Part III.

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tion of nitrate of quicksilver is formed. In the second, thereis a mutual decomposition of this nitrate, and of the muriateof soda ; nitrate of soda is formed, and muriate of quick-silver with excess of oxide: or, according to Sir H. Davy,the chlorine of the sodane combines with the mercury of thenitrate, forming mercurane, while the hydrogen ef the mu-riatic acid and the oxygen of the mercurial oxide combine toform water, nitric acid, anil soda. In this preparation, ourobject is to obtain the insoluble compound which result.- fromthe combination of the protoxide ol mercury with muriaticacid. In this view, the application of heat, in dissolving themercury in the nitrous acid, is improper; for a porta.n atleast of the mercury is converted into its peroxide, which oc-casions, in the first place, the formation of alittlesubnitrateofmercury, when poured into the saline solution ; and, secondly,the formation of a proportion of muriate of mercury (corrosivesublimate), which must be washed away. Accordingly, MrMurray has found, that more of mild, and less of corrosivemuriate of mercury are formed, when the solution is madeslowly and in the cold, than when the directions of the collegesare complied with.

In Sir H. Davy's view of the subject, according to which,calomel and corrosive sublimates are comp< unds of metallicmercury, with different proportions of chlorine, the object inthis preparation is to get the largest quantity of mercury dis-solved in the nitrous acid, so that in decompo-ing muriateof soda, the smallest quantity of chlorine may be set at liber-ty ; and as the peroxide contains twice as much oxygen asthe protoxide, and acids seem to combine with a certain quan-tity of >.xygen in oxides, whatever be the quantity of metalunited with them, the nitrate of the protoxide of mercury willcontain twice as much mercury as the nitrate of the peroxide,and will of course give a double proportion of mercury to thechlorine set at liberty by the acid and oxygen.

When properly prepared, the submuriate obtained by pre-cipitation scarcely differs from that obtained by sublimation.Gbttling found no other difference than that the precipitated,submuriate become- grey, when triturated with lime-water,whereas the sublimed submuiiate becomes black. But heexposed to heat half an ounce of the pre cipitated submuriatein a subliming apparatus ; scarcely a grain of a reddish mat-ter remained fixed ; and the sublimed matter now becameblack when triturated with lime water and differed in no rc-sptct from submuiiate prepared in the ordinary way bysublimation. It therefore would seem to be an improve-