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Terized and put in a vial with volatile liverof fulphur, by which in the fpace of halfan hour it was converted into fine cinnabar.Similar effe&s to the above were obferved totake place when a fixed alkaline liver of ful-phur was made ufe of, only the change of colourfrom a black to red was confiderably flower,and the colour irfelf was lefs pure and brilliant.The lab improvement in the preparation ofcinnabar in the rnoift way, was made by M.Kirchoff, of Peterfburgh, and Count MouflinPoufchin.® Three hundred grains of mercuryand 68 grains of fulphur, are to be triturated ina porcelain cup with a glafs peftle, a few dropsof cauftic potaflr being added to expedite andperfe£t the combination of the two ingredients :when a perfect ethiops is thus formed, there isto be added 160 grains of potaflr diffolved in anequal quantity of water, and the cup with itscontents is to be heated over a lamp, care beingtaken to continue without interruption the tritu-ration with the glafs peftle. In proportion as theliquid evaporates frefli water mud be added fothat the ethiops may be conftantly coverednearly to the depth of an inch. In the fpaceof about two hours the colour begins to changefrom black to brown, and then no more w r ateris to be added, but the trituration is to be conti-nued as before. As foon as the mafs acquiresa gelatinous confibence the colour becomesmore red and brighter with great rapidity : thisis the mob critical point of the whole procefs ;for if the heat is not continued a fuflicient lengthof time the utmoft perfection of colour is notattained, and if it is perfibed in only two fe-conds too long, the tint is degraded to a dirtybrown, incapable of being amended.

Thus far the preparation in the moib way ofthis beautiful colouring fubftance was carriedby M. Kirchoff, to which the following importantadditions were made by Count MouffinPoufchin.Firb, the cup with its contents fhould be re-moved from the lamp or fand bath before thecinnabar has acquired its full degree of red-nefs, and kept for three or four days at a tem-perature of loo 0 Fahr. birring it up and addinga little water from time to time ; at the expi-ration of this period the mafs being allowed tobecome nearly dry, will be found to have ac-quired all the vividnefs which the fuccefsfulaccomplilhment of Mr. KirckhofPs procefscould have produced without the rilk of de-uroying it by too long continuance of the heat.In order to feparate the alkaline fulphuret from

the cinnabar, it mub be mixed with boilingwater in the proportion of about a quart of thelatter to an ounce of the former: alter birringthe whole up for a few feconds the water willbecome quite black, and is to be poured oftas foon as the cinnabar has fubfided: the edul-coration is to be compleated with frefh parcelsof hot water, till all the hepatic tabe and odouris entirely wafted away, and now the cinnabarwill be very beautiful, differing from the com-mon fublimed by a flight tint of yellow. Afarther improvement in the cinnabar may nowbe brought about by the procefs of wafflingover: for this purpofe let two or three ouncesbe put into a glafs jar with fome cold water,and mix the whole accurately by birring, then,after an interval of a few feconds to allow theheavier particles to fubfide, pour the turbidwater into a difli, and drain it off again as foonas it has become Clear. The cinnabar thus fepa-rated will be found to be very brilliant, andapproaching to carmine: the refidue may betreated twice more fucceiTively in the fame man-ner, and two more parcels of cinnabar inferiorto tire firb, but bill very good may be obtained,the refidue is a brown fulphuret of mercury ofno value as a pigment. To give the cinnabarthe higheb degree of beauty it is now to bedried flowly, and then is to be laid in fmallquantities at a time on a plate of glafs or glazedearthenware, pretty brongly heated ; the colourin an inbant becomes brown, and then a verydark violet grey ; it is now to be thrown upon acold plate, where it paffes in an inbant to abrilliant carmine red.

Concerning the nature of the chemical adlionthat takes place in the preparation of mercuryby the moib way, there has been much con-troverfy, nor is the fubjeft even yet entirelyfree from difficulties. From the experimentshowever of Proub, l’erthollet, and other che-mibs, it appears ib, that the pure and recentlyprepared alkaline hydrofulphurets have no aftionon metallic mercury; but that when by expo-fure to the air thefe hydrofulphurets becomecoloured and converted into hydroguretted, ormore properly into hydrofulphuretted fulphurets,the mercury decompofes them by uniting withthe fulphur, and thus reducing them,-again tothe bate of fimple hydrofulphurets ; the mercuryis by the fame procefs changed into the blackfulphuret, and is fparingly fcluble in the fuper-natant hydrofulphuret. As foon however asthe black fulphuret is changed to cinnabar it

* Nii'h. Journ. 4to, IL p. I.

TOL. II.

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