The Sulphide of Mercury, known in commerce under the name of Ethiops mineral, is officinal in France, the Netherlands, and Germany. Its properties have been already described. The German and Dutch pharmacopœias require in it 50, the French only 331⁄3 per cent. of metallic mercury.
Hahnemann’s Soluble Mercury (Hydrargyrum solubile Hahnemanni) is officinal in the Dutch pharmacopœia. As found in commerce it contains metallic mercury, nitric acid, and ammonia. The mercury should be in the proportion of 86·33 per cent., the ammonia 2·44 per cent.
Crystallised Nitrate of Mercury (Hydrargyrum nitricum oxidulatum) is officinal in the pharmacopœias of Germany, Switzerland, and France. The salt is in white crystals, giving the reactions of nitric acid and mercury, decomposed by the addition of water, but fully soluble in water, if first moistened with nitric acid. The formula of the neutral salt is Hg2NO3HgO2H2O, which requires 69·4 per cent. of mercury. An acid solution of mercuric nitrate is officinal.
An Ointment of Nitrate of Mercury (Unguentum hydrargyri nitratis) (often called citrine ointment) is contained in the B.P.; it is made with 4 parts of mercury, nitric acid 12, lard 15, olive oil, 32; the strength is about 1 in 151⁄2.
A Chloride of Mercury and Quinine exists in commerce, prepared by mixing 1 part of corrosive sublimate in solution with 3 parts of quinine chloride, evaporating, and crystallising.
Cyanide of Mercury, HgCy, is contained in the French pharmacopœia. It occurs in small, colourless, prismatic crystals, easily soluble in water. If to the solution chloride of tin be added, a black precipitate of reduced metal and stannous oxide is thrown down, and the odour of prussic acid is developed.
Mercuric Sulphide (Sulphide of Mercury, Cinnabar, Vermilion) is officinal in Germany, the Netherlands, and France; HgS = 232; specific gravity, solid, 8·2; Hg, 86·21 per cent., O, 13·79 per cent. For medicinal purposes it is made artificially. It is a beautiful red powder, insoluble in all alkaline and all acid liquids, with the exception of aqua regia. The solution gives the reactions of a sulphide and mercury. On heating, it must burn away entirely without residue; adulterations or impurities are—minium, lead, copper, and other metals. The detection of minium is conveniently executed in the dry way. Pure cinnabar, when heated in a matrass, gives a black sublimate, which becomes red on friction. If minium is present, sulphide of lead remains as a residue, and may be recognised on coal; the same remark applies to sulphide of antimony. If it be desired to take the percentage of mercury in cinnabar, equal parts of oxalate and cyanide of potassium should be well mixed with the cinnabar, and heated in the bent tube described at [p. 654]; by this means the whole of the metallic mercury is readily obtained.[907]
[907] Dr. Sutro has published a case (quoted by Taylor), in which the vapour of vermilion, applied externally, produced poisonous symptoms; yet, according to Polak, the Persians inhale it medicinally, smoking it with tobacco, catechu, mucilage, &c., the only bad effect being an occasional stomatitis.—Eulenberg, Gewerbe Hygiene, p. 741.