MERCURY, a metal which has long been distinguished, as the only one that retains its fluidity at the common tempe rature of the atmosphere. The late dis coveries of Mr. Davy have, however, pro duced two others which possess this pro perty : these will be noticed in their places: see Senators, and POTASSIUM ; see also ALKALI. When the temperature is reduced to about 40° below zero of Fahrenheit, it assumes a solid form : this however is a degree of cold that never re occurs but in high northern latitudes, and in this country mercury can only be ex hibited in a solid state by artificial means: see COLD. When congealed, its specific gravity is so much increased, that it sinks to the bottom of the fluid mass. It has been increased from 13.5 to 15.6. At about 600° of Fahrenheit, it boils and is changed into vapour, and this method is taken to purify it from the admixture of other metals. When very pure, mercury is not oxydized at the common tempera ture of the atmosphere, but may be con verted into an oxide by boiling. It is dis solved by hot sulphuric acid, and forms a white salt, which, being washed with boiling water, produces ayellow substance called turbith mineral. It may likewise be dissolved by nitric acid with and with out heat ; but the mercury is more high ly charged with oxygen in the former case than in the latter. It may be united to the muriatic acid by a double elective affinity : thus when sulphate of mercury and muriate of soda, both dry, are mixed and exposed to heat, a combination of oxide of mercury and muriatic acid is ob tained by sublimation : this is called in the shops "corrosive sublimate." "Ca lomel" is compounded of the same sub stances, but with a larger proportion of mercury. Corrosive muriate of mercury is in the form of a white compact mass, tending to a crystalline arrangement : it is soluble in about twenty parts of water, at the temperature of and in two of boiling water. In alcohol much r portions are dissolved. The taste oft is salt is styptic and disagreeable, and it acts as a most virulent poison, so that although it is used in medicine, it cannot be administered in larger quantities than the sixth or eighth of a grain. The oxide which exists in the corrosive muriate of mercury consists of Mercury 85 Oxygen 15 100 , um In the muriate there are Oxide 82 Acid 18 100 m Therefore 100 parts of the muriate con sist of Mercury . . . . 67 Oxygen . . . . 12.3 eighty-two parts of oxide, with which eighteen parts of muriatic acid are combined.
The oxides of mercury are all reduced by heat alone, without the addition of any combustible substance,and afford oxy gen gas. Mercury itself dissolves gold,
silver, tin, and other metals, and if pro perly combined with it in sufficient quan tity, the mercury loses its fluidity, and forms an amalgam. It is observed, that a solid amalgam of lead, and another of bismuth, have the property of becoming fluid. By combination with sulphur meteuiT affords two compounds. By long trituration, these bodies unite, and form a black sulphuret. When united by fusion, and afterwards sublimed, a red sulphuret is produced, called cinnabar, which, being reduced to powder, afford; the common pigment vermilion.
Mercury is the basis of a new fulminat ing compound. The oxides precipitated from their combinations with acids, by the alkalies or earths, especially by am monia or lime, are capable, when combin ed with sulphur, of detonating. If tritu rated with one-sixth part of their weight of sulphur, on being exposed gradually to heat they explode with considerable force. These materials must be prepar ed and dried in the open air, and expos ed to the light. Mr. Howard has disco vered another fulminating powder of mercury, possessed of still greater pow ers. This is prepared by dissolving 100 grains of mercury in one ounce and a half of nitric acid : the solution, when cold, is to be poured upon two ounces of alcohol : a moderate heat is then to be applied, till an effervescence is excited, when a precipitate is formed, which is to be immediately collected on a filter, well washed with distilled water, and carefully dried in a heat not much ex ceeding that of a water-bath. From 100 grains of mercury, between 120 and 130 grains of dry precipitate are formed. This preparation fulminates very strong ly. If two or three grains only be laid on an anvil, and struck smartly with a ham mer, it explodes with a loud report. Four grains will occasion indentation in the hammer and anvil. This powder is found to consist of oxide of mercury, combined with oxalic acid and nitrous etherized gals: the two latter being produced dur ing its formation, by the action of the ni tric acid on the alcohol. Its exploi sion and force are supposed to be owing to the oxygen present suddenly combin ing with the carbon and hydrogen, form ing watery vapour and carbonic acid : exotic gas is also discharged, and much caloric is evolved, so as to volatilize the mercury : to this, the conversion of the mercury into vapour, Mr. Howard ascribes its great explosive velocity.