M E R

HER

( 90 )

•safes to be foluble in an alkaline hydrofulphu-ret, whence the fupernaiant liquor at the con-ciufion of this procefs confifts merely of thealkali combined with a variable proportion offulphuretted hydrogen, as is manifeft from itsgiving out fulphuretted hydrogen, but no ful-phur, by the action of acids.

2. If inilead of an alkaline hydrofulphuret,a liquid alkaline fulphuret, holding as little aspoflible of hydrofulphuret be employed, theaction of the mercury is immediate, the wholeof the fulphur combines with the metal, andthe ethiops thus produced is partly taken up bythe alkali, but is depofited again as foon as theethiops is converted into cinnabar, fo that theclear and colourlefs fupernatant fluid containsnow only alkali with the cafual quantity of ful-phuretted hydrogen originally contained in it,and which appears to have been entirely inertduring the whole procefs.

3. If to a pure alkaline hydrofulphuret therebe added fome red oxyd of mercury, the liquorbecomes hot, acquires a yellow colour, and ifthe proper quantity of metallic oxyd has beenufed, both the hydrofulphuret and metallic oxydwill be entirely decompofed ; the oxygen of theone and the hydrogen of the other hy theircombination will produce water, the mercurywill faturate itfelf with fulphur and becomeethiops, and the fupernatant liquor is a purealkaline fulphuret from which the acids arecapable of precipitating the fulphur, hut of notfeparating a Angle atom of fulphuretted hydro-gen.

4. If a folution of common alkaline hepar orhydrofulphuretted fulphuret, be firft broughtto the ftate of Ample fulphuret by the additionof a little red oxyd of mercury, and there beafterwards added a frefh portion of oxyd, agreat increafe of temperature is obferved, partof the fulphur is converted into fulphureousacid by a portion of the oxygen, while the re-mainder of the oxygen quits the metal and af-fumes the gafeous ftate, cauAng an eftervefcenceduring its difengagement: when this has takenplace the fupernatant liquor contains the alkaliof the hepar with a little fulphureous acid, andoften a fmall quantity of red oxyd if an excefsof this fubftance has heen made uie of.

The deduction from thefe experiments is,that neither oxygen nor fulphuretted hydrogenenter into the compofition of ethiops or einna-bar; and it is highly probable that the onlydifference between them confifts in the propor-tion of fulphur.

Phofphorus may be made to combine with

mercury 6 by diftilling together equal parts of redoxyd of mercury and phofphorus, together witha little water: during the procefs the red oxydbecomes black and unites to the phofphorus,and phofphoric acid is produced. This combi-nation may be more eafily effected accordingto Dr. Thomfon, by ufing the grey oxyd ofmercury. Phofphorus and mercury in the me-tallic ftate cannot be made to combine, exceptthe latter is in a ftate of extreme diviAon. Phof-phuret of mercury is a fubftance of a moderatelyfolid conAftence, a black colour, and may be cutwith a knife ; when expofed to dry air it exhaleswhite vapours of phofphorus. It is decompofedby diftillation, the phofphorus firft comes overand then the mercury, each fubftance beingfound in the receiver perfectly feparate.

Mercury is capable of uniting with many ofthe other metals, and thefe combinations haveobtained the name of Amalgams . They havereceived confiderable attention from variouschemifts, though by no means fo much as theirchemical importance deferves. Before we pro-ceed to notice the particular amalgams we fhallmention a few general obfervations that areapplicable to all of them.

Firft with regard to the preparation of amal-gams. It may be remarked that the care ne-ceflary in their preparation depends confiderablyon the degree of affinity fubfifting between themercury and the other metal. Where theaffinity is very powerful, as is the cafe withgold and filver, the fluidity of the mercurywithout any other condition will effedt a com-bination even at the common temperature.Other metals of ftronger cohefion or weaker affi-nity require the affiftance of heat to make themamalgamate; while thofe metals that are in-fufible, except at a temperature equal to therapid volatilization of mercury, as copper, re-quire peculiar precautions to bring about a combi-nation. Amalgams may be made either folid orfluid, according to the proportion of mercury thatenters into this compofition; the quantity how-ever of this laft that is required to give the amal-gam a fluid ftate, is different for each metal.

2. All the appearances that happen during thecompofition of metals with mercury indicate areal folution of one in the other, owing to thechemical attraction between the bodies fo uni-ting. Hence during amalgamation as is thecafe in all other inftances of folution, a veryobfervabie change of temperature takes place.Another remarkable phenomenon is the tenden-cy to oxydation which both metals exhibitduring their combination. Thus if bifmuth,

* Mem. de Pellet, ii. P. 43.