MERCURY, or QUICKSILVER (symb. Hg, equiv. 100—new system, 200--sp. gr. 13.6), one of the so-called noble metals, remarkable as being the only metal that is fluid at ordinary temperatures. It is of a silvery white color, with a striking metallic luster. When pure, it runs in small spherical drops over smooth surfaces; but when not. per fectly pure, the drops assume an elongated or tailed form, and often leave a gray stain on the surface of glass or porcelain. Moreover, the pure metal, when shaken mIth air, presents no change upon its surface; while, if impure, it becomes covered with a gray tilm. It is slightly volatile at ordivary temperatures, and at 662° it tioils, and forms a colorless vapor of sp. gr. 6.976. Hence it is capable of being distilled; and the fact of its being somewhat volatile at ordinary temperatures, helps to explain its pernicious effects upon those whose trades require thetn to come much in contact with it—as, for example, the makers of barometers, looking-glasses, etc., At a temperature of —39°, it freezes, when it contracts considerably, and becomes malleable.. In consequence.of the uniform rate at which it expands when heated, from considerably below 0° to above 300°, it is employed in the construction *of the mercurial thermometer.
All mercurial compounds are either volatilized or decomposed by heat; and when heated with carbonate of soda, they yield metallic mercury. Native or virgin quicksilver only occurs in small quantity, usually in cavities of mercurial ores. Of these ores, by far the most important is cinnabar (q.v.). There are two means of obtaining the metal from the cinnabar: the ore may be burned in a furnace, in which case the sulphur is given off as sulphurous acid, and the meremy is collected in a condensing chamber: or the ore may be distilled with some substance capable of combining with the sulphur—as, for example, with slaked lime or iron filings.
The mercury imported into this country is usually almost chemically pure. If the presence of other metals is suspected, it may be pressed through leather, re-distilled, and then digested for a few days in dilute cold nitric acid, which exerts little action on the • mercury, if more oxidizable metals are present. The mercury, after being freed from the nitric acid by washing with water, is chemically pure.
There are two oxides of mercury, the black suboxide (Hg20) and the red oxide (HO). Both of these lose all their oxygen when heated, and form salts with acids. The black subo.ride, although a powerful base, is very unstable when isolated, being readily con verted by gentle warmth, or even by mere exposure to light, into red oxide and the metal (lIg20 = fig° Hg). The most important of its salts is the nitrate (Hg20,NO2+ 2Aq), from whose watery solution ammonia throws down a black precipitate known in phar macy as mereurius solubilis Halinemanni, from its discoverer, and consisting essentially of the black suboxide with some ammonia and nitric acid, which are apparently in com bination. Of the red oxide, the most important salts are the nitrate (I-IgO,NO SAq); the sulphate (Hg0,S02), which is employed in the manufacture of corrosive sublimate; and the basic sulphate (3Hg0,S02), which is of a yelloW color, and is known as turpeth mineral.
The haloid salts of mercury correspond in their composition to the oxides. Of the most important of these—the chlorides—there are the subchloride (Hg2CI), well known Pm calomel (q.v.), and the chloride (HgC1), or corrosive sublimate.
The elztorida (formerly termed the hichloride, when calomel was regarded as the pro tochloride, and the equivalent of Hg was regarded as 200 instead of 100), when crystal lized from a watery solution, occurs in long- white glistening prisms; but when obtained by sublimation, it occurs in white transparent heavy masses, which have a crystalline fracture, and chink with a peculiar metallic sound against the sides of the bottle in which they are contained. This salt melts at 509°, and volatilizes unchanged at about 570.° It has an acrid metallic taste. It is soluble in 16 parts of cold, and in less than three parts of boiling water, and dissolves very freely in alcohol and in ether. Corrosive sub limate enters into combination with the alkaline chlorides, forming numerous distinct compounds. (A double chloride of ammonium and mercury, represented by the formula 3H4NC1,HgCI Aq, has been long known as sal alembroth.) It combines with oxide of mercury in various proportions, forming- a class of compounds of great interest in theo• retical chemistiy, termed oxyglorides of mercury. On adding a solution of corrosive sub.