Experiment 14. If mercury be agitated with sulphuretted hydroguret of ammonia, according to Berthollet, a black sulphuret of mercury is formed; but,

Experiment 15. If hydro-sulphuret of ammonia be used, the black precipitate formed gradually assumes a red colour, and the solution will contain sulphuretted hydroguret of ammonia.

Experiment 16. If sulphuret of potash, dissolved in water, be added to a solution of mercury, the latter will be precipitated in the form of an hydrosulphu

ret.

Remark. It is supposed by some chemists, as Fourcroy, that in this preparation the mercury is always oxydized; hence it is sometimes called the black sulphuretted oxyd of mercury. Proust, however, has asserted the contrary. Ethiop's mineral, again, is considered merely a sulphuret of mercury.

Experiment 17. If the black sulphuret be sublimed, a product will be obtained called the red sulphuret of mercury, or cinnabar, known also by the name of vermillion; or,

Experiment 18. According to Mr. Kirchoff, let 300 grains of mercury, and 68 of sulphur, with a few drops of a solution of potash to moisten them, be triturated in a Wedgwood's, or glass mortar, until it be converted into a black powder. Add to this 160 grains of potash, dissolved in as much water. Heat the vessel containing the ingredients over the flame of a candle, and continue the trituration without interruption during the heating. As the liquor evaporates, add water from time to time, so that the black oxyd may be constantly covered, to the depth of an inch. The trituration must be continued until the mixture begins to change from its original black colour to a brown, which usually happens when a large part of the fluid is evaporated; it then passes very rapidly to a red. No more water is now to be added, but the trituration is to be continued. When the mass has acquired the consistence of a jelly, the colour increases in brightness, with an incredible degree of quickness. The instant it has acquired its utmost

beauty the heat must be withdrawn, otherwise its bril liancy will be impaired, and the red will pass to a brown colour. This red powder is also sulphuret of mercury or cinnabar.

Count de Moussin Pouschin has discovered that its passing to a brown colour may be prevented by taking it from the fire as soon as it has acquired a red colour, and placing it for two or three days in a gentle heat, taking care to add a few drops of water, and to agitate the mixture from time to time. During this exposure the red colour gradually improves, and at last becomes excellent. He discovered also, that when the sulphuret is exposed to a strong heat, it becomes instantly brown, and then passes to a dark violet; when taken from the fire it acquires a beautiful carmine red.*

Remark. The changes which sulphur and mercury undergo when exposed to heat, is shewn in the following experiments of Parke.t

Experiment 19. Take equal parts of mercury and flowers of sulphur, add a drop or two of water and grind the whole together in a glass mortar. Presently the mercurial globules will totally disappear and the mass assume a black colour. It thus becomes a black sulphuret of mercury, or the true Ethiops mineral.

Experiment 20. If the black sulphuret of mercury formed in the last experiment be heated in an open vessel, part of the sulphur will pass off, sulphurous acid gas will be emitted, and the mass remaining in the vessel will have acquired the colour of the violet.

Experiment 21. If the violet residuum of the last experiment be removed to a glass mattrass or flask, and heat gradually applied, the whole will sublime into a dark shining mass, which, by being reduced into powder, furnishes a most brilliant scarlet.

* Nicholson's Journal, ii. 1.

+ Parke's Rudiments of Chemistry, p. 19.

Experiment 22. If mercury and flowers of sulphur, according to the count Apollos de Moussin Pouschin, be triturated with a solution of caustic potash, keeping it at a proper temperature, and afterwards washing it repeatedly with boiling water, which carries off Ethiops, not surcomposed, the red sulphuret of mercury will be produced.*

Remark. The alkali appears to act by dissolving, or otherwise disengaging the sulphuretted hydrogen and superfluous sulphur.

Experiment 23. If sub-muriate or sub-sulphate of mercury be sublimed with sulphur, the red sulphuret of mercury, and muriate or sulphate of mercury will be formed.

Rationale. The excess of base in the mercurial salt unites with the sulphur, whilst the sub is reduced to the state of a neutral salt.

Remark. Cinnabar, according to Proust, is composed of 85 parts of mercury, and 15 of sulphur. The specific gravity of this sulphuret is about 10. It has neither smell nor taste, and is insoluble in water and in alcohol. In close vessels it sublimes entirely unchanged, but requires for this purpose a pretty great degree of heat. It is not soluble in any acid, and is only decomposed by the nitro-muriatic which dissolves the quicksilver, and separates the sulphur. It is not decomposed by boiling it with solutions of the alkalies, but is decomposed by melting it with potass, soda. lime, iron, lead, copper, antimony, and several other metals.

Experiment 24. If equal parts of red oxyd of mercury and phosphorus, with one part of water, be put into a flask, and exposed on a sand bath to heat, a blackish compound, or phosphuret of mercury will be formed.

Rationale. The oxygen of the oxyd of mercury unites with a part of the phosphorus, forming phosphoric acid, which is dissolved by the water, and the

* Nicholson's Journal.

mercury combines with the other portion of phosphorus.

Remark. As phosphorous combines readily with the black oxyd of mercury, and as Pelletier could not succeed in combining mercury with phosphorus, without the presence of oxygen, it is inferred, that it is not a phosphuret of mercury, but a black phosphuretted oxyd of mercury.

Experiment 25. The preparation of Howard's fulminating mercury is made in the following manner:

One hundred grains (or a greater proportional quantity, not exceeding 500) are to be dissolved, with heat, in a measured ounce and a half of nitric acid. This solution being poured cold upon two measured ounces of alcohol, previously introduced into any convenient glass vessel, a moderate heat is to be applied till effervescence is excited. A white fume then begins to undulate on the surface of the liquor, and the powder will be gradually precipitated on the cessation of action and re-union. The precipitate is to be immediately collected on a filter, well washed with distilled water, and cautiously dried in a heat not exceeding that of a water-bath. The immediate washing of the powder is material, because it is liable to the re-action of the nitric acid; and while any of the acid adheres to it, it is very subject to the action of light. From 100 grains of mercury about 120 or 130 of the powder are obtained.*

Rationale. As this powder is composed of oxyd of mercury, oxalic acid, and nitrous etherized gas, it would appear, that the nitrate of mercury in its decomposition by the alcohol is resolved into oxyd of mercury; that its nitric acid, by imparting oxygen, converts the alcohol into oxalic acid, during which nitrous ether is formed; and that the oxalic acid then combines with the oxyd of mercury, together with a portion of ether, and forms the fulminating mercury.

Phil. Trans. 1800, p. 214.

Remark. Three or five grains of this powder produce a great explosion, when struck on an anvil or hammer. It takes fire at 368° Fahrenheit. It explodes not only by friction, but by electricity, galvanism, by the flint and steel, and by being thrown into concentrated sulphuric acid. Its detonation is thus explained: the oxygen unites with the hydrogen and carbon, forming water and carbonic acid, and a considerable quantity of caloric is liberated, which not only gives elasticity to these bodies, but also converts the mercury, which is revived, into vapour.

Experiment 26. If to a solution of mercury in nitric acid, oxalate of potash be added, a precipitate will be formed, which, if collected, washed, and dried, will fulminate; or,

Experiment 27. If red oxyd of mercury, be digested in a solution of super-oxalate of potash, or in oxalic acid, the same combination will be produced.*

Rationale. In the first process, the nitric acid of the nitrate of mercury unites with the potash, forming nitrate of potash, which remains in solution, whilst the oxalic acid of the oxalate of potash combines with the oxyd of mercury, thus separated, into an oxalate of mercury. In the second process a direct combination of the constituent parts takes place. This powder is of a gray colour, and produces a considerable detonation when struck.

Experiment 28. If a little mercury be rubbed on gold, it will give it a silvery appearance. If the gold be ignited, and conveyed into hot mercury, the combination will be facilitated.

Experiment 29. If the gold thus covered with mercury, be exposed to a red heat, the mercury will be disengaged.

Experiment 30. If silver be brought into contact with mercury, a union will take place as in experiment 27. And,

* See a memoir of the author, on Fulminating Mercury, in Coxe's Medical Museum.