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cafe yellow arfenic , in the latter fandarac orrealgar. Similar combinations are alfo foundnative, and have been already mentioned. Theexa£t proportions of each vary according to cir-cumftances, and it is not precifely determinedwhether the colour is more owing to thefe pro-portions or to the degree of oxygenation of thearfenic. They are given however in the bedauthors w to be in the red fulphuret I of fulphurto 4 of arfenic, and in the yellow I to 9 or 10.Sulphur renders arfenic much more fixed in thefire, fo that the red fulphuret may be melted bymoderate heat into a tranfparent mafs, calledarfenical ruby. When the white oxyd or thearfeniates are ufed in the preparation, they oxy-genate part of the fulphur, and hence it givesout much fulphureous acid gas. In the largeway thefe fulphurets are prepared as pigments,and the exaft procefs is not generally known,but it is faid to be by fubliming in earthen vel-fels- iron pyrites mixed with mifpickel or fomeof the other native ores of arfenic and iron.The iron is certainly of great fervice in diminifh-jng the volatility both of the arfenic and thefulphur, for a full red heat is requifite to drivethem off; and we find in the way of experi-ment, that a fimple mixture of white arfenicand flowers of fulphur fublime too haftily tocontraft a very clofe union, and feldom producean orpiment of a full uniform body of colour.

For experiment, the operation may be per-formed in a glafs matrafs, flightly {topped atthe mouth, and heated only at the bottom gra-dually to rednefs. Equal parts of white arfenicand fulphur well mixed, yield in this manner ared fublimate, which attaches itfelf to the neckof the veflel. If two parts of arfeniat of potafhand one of fulphur, are flowly heated, barelyred, for an hour in a matrafs, a very fine realgaror red fulphuret fublimes, and the refidue atbottom confifts of yellow orpiment, mixed withliver of arfenic, or arfenic united with potafh.The arfenic acid gives alfo a fine realgar. Sixparts of liquid arfenic acid mixed with oneof fulphur, x give no figns of mutual action tillthe water is expelled, when on encreafing theheat the whole rifes rapidly, and forms a finered fublimate of realgar, with a copious emifiionof fulphureous acid gas. The dry arfenic acidand fulphur, in equal parts, heated for an hour,give the fame products.

The yellow and red fulphurets do not diflolvein water. The nitro-muriatic acid by heat fepa-ratea the fulphur from the arfenic, by diflolvingthe> latter: fome of. the fulphur flies off as ful-

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phuretted hydrogen gas, whilft the remainderfalls to the bottom as a grey powder.

The fixed alkalies will feparate the fulphurfrom the arfenic in the dry way, by diflolvingthe former. For this, mix the arfenical ful-phuret with a little potafh diffolved in water,dry the mixture and flowly heat in a fublimingveiled. The arfenic rifes in the form of whiteoxyd, but only partially, much remaining behindunited with the alkali, now fulphuretted. Iftoo much potafh is ufed, no arfenic feparates,-but the three fubftances remain united in fufion-Cauftic alkali diffolves the arfenical fulphuret inthe moift way, for if they are boiled together,the refult is an alkaline fulphuret, holdingarfenic in folution. An acid gives a bright yel-low precipitate in this liquor, which is probablya hydvofulphuret- of arfenic-

Quick-lime and orpiment boiled together pro-duce a fulphuret of lime, holding fome arfenicin folution. This has long been known as in-fallible to caufe the hair to fall off where it is.rubbed, and is alfo ufed as a wine-tejl to dete£tthe prefence of Lead, which it does by makinga black precipitate. By long keeping, this folu-tion depofits minute cryftals of white arfenic.

The fat oils by heat diffolve the arfenical ful-phurets into a very tqugh fetid mafs.

Sulphuretted alkalies alfo diffolve the regulus-of arfenic by fufion, but the affinity is fo weak-as to be difplaced by almoft every other metal.A fimilar folution takes place by boiling a wateryfolution of the alkaline fulphuret with the regu-lus, and acids precipitate from this folution ared hydrofulphuret of arfenic. The fame hydro-fulphuret is produced in a Ampler way by pallingfulphuretted hydrogen gas through a wateryfolution of white oxyd of arfenic, or by mixingthe fulphuretted water with the fame.

Arfenic will unite with phofphorusj and aphofphuret of arfenic is produced in the followingmanner. Mix half a dram. of. white arfenicwith a dram of phofphorus, Y and diftill with a-gentle heat in a clofe veflel. A red fublimateis produced, and at the bottom remains a blackbrittle fubftance.. The former appears, by theexperiments of Pelletier, to be oxyd of phol-phorus, the latter is the phofphuret of arfenic.It is obtained in greater abundance by diftillingcautioufly equal parts, of regains of arfenic withphofphorus. The black finning refidue is the-phofphuret of arfenic, and contains fo muchphofphorus as to require to be kept under water.Both thefe preparations may be made in themoift way. Equal parts of regulus of arfenic.

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