MERCURY (Hg.) Quicisilrer. The history of this well-known metal, a description of the sources whence it is obtained, its physical properties, and a list of the minerals in which it occurs have already been given under MERCURY, in NAT. Him Div. An interesting statistical account of the most important of all the mercury mines, namely, those of Almaden in Spain, is also given under ALMADEN in (3E00. Div. It is here, therefore, only necessary to treat of its chemical properties and the action of various substances upon it by virtue of which compounds of the metal are obtained.
The equivalent of mercury is 200. By combining with one or with two equivalents of other bodies it forms two classes of salts, known as protosalts and bind's. Sometimes the equivalent of mercury is assumed to be 100, and then the first class of salts containing two such equiva lents to one of another body are necessarily termed disalts or subsalts ; while the second class, containing only one such equivalent to each equivalent of another body, are consequently termed protosats. This want of uniformity in the nomenclature of salts of mercury is to be deprecated, inasmuch as it is confusing to students, and has also frequently led to serious errors when employed by those who, like medical men and compounders of medicine, have necessarily but a partial knowledge of chemistry. A method now very generally adopted, by which the inconvenience is obviated, consists in adding to the word »Lemur the terminals that are commonly used for similar purposes—namely, is and oils. The first or lower class of salts are thus mercurous salts, and the second, or higher, mercuric salts.
Mercury and oxygen form two compounds.
1. Protoxide of mercury (Hg0). Black oxide, grey oxide, suboxide, or dinoxide, of mercury. Mercurous oxide. This oxide is best obtained by triturating calomel with dilute caustic potash or soda, and well washing and drying the resulting oxide. The operation should be conducted as much as possible in the dark, as the oxide is decomposed by the influence of light, into metallic mercury and binoxide. Though itself unstable, it forms very stable salts, called salts of mercurous oxide or shortly, mercurous 817118.
2. flinoxide of mercury (Hg0,). Peroxide, red oxide, yellow oxide, or proto.rifie, of mercury. .31cl-curie oxide. This oxide may be made in
Several ways. The alchemists used to keep mercury at a boiling heat for a nmnth, or longer, in a matrass, or a flask with a tolerably long neck, but having free communication with the air. It thus slowly absorbed oxygen, becoming converted into binoxide and was called by them mercurous preeipitatus per se. It is now however generally pre pared by calcination from mercuric nitrate when it has a bright orange colour, and is in the state of shining crystalline grains. Sometimes it is precipitated from a solution of a permit of mercury by caustic potash or soda ; it then differs from the crystalline variety in being converted into oxalate of mercury by the action of oxalic acid.
Binoxidc of mercury darkens in colour when heated, but again becomes red on cooling. When ignited it is resolved into metallic mercury and' oxygen gas. Chlorine acts upon it, especially when moist, hypochlorous acid and an oxyehloride of mercury being formed. Reducing agents also readily attack it. It is a powerful base forming 'salts of mercuric shortly, mercuric salts.
Mercury and sulphur form two sulphides corresponding to the two oxides:— 1. Protosulphide of mercury (HgS). Mercurous sulphide. Ethiop's mineral. This compound is precipitated when sulphuretted hydrogen is passed through a solution of a mercurous salt. It is also frequently made by triturating two hundred parts of mercury with sixteen of sulphur. It is almost as unstable as the protoxide.
2. Bisulphide of mercury (HgS,). Mercuric sulphide. Cinnabar. Vermilion. This is the most common ore of mercury. [MEnctutY, in NAT. HIST. Div.] It is largely used as a pigment, but for this purpose is usually prepared artificially. The Chinese are very successful manufacturers of vermilion : the following is supposed to be the process they adopt. One hundred parts of mercury and thirty eight of sulphur are triturated for two or three hours; twenty-five parts of solid caustic potash and one hundred and fifty of water are then added, and the whole heated to about 115° Fahr. for several hours. It must be constantly stirred at first, and, when the desired tint is obtained, removed from the fire and well washed with cold water.