AR'SENIC (Gk. 'Apaermor, (firsenikon, yellow orpiment, from apany, arsF.», male, masculine; alluding to its strong properties). A chem ical clement that was known to the ancients. It was distinctly referred to as early as 1694 by Schroder. It is found widely distributed in nature, though in small amounts. It is often found in the form of manna illated or kidney shaped masses, but occurs also in well-crystal lized form. It is found chiefly in the older rocks or in schists associated with other metallic min erals. The principal European localities are: Andreasberg, in the Harz Mountains; Joachims thal, in Bohemia, and Freiberg, in Saxony. It is also abundant in Chile, Mexico, and New Zealand. In the United States it is found in Haverhill and Jackson, N. H.; Greenwood, Maine, and Leadville, Colo. In combination with sulphur, arsenic occurs as realgar and as orpiment, and with sulphur and iron as lollingite and as arsenopyrite or mispiekel, called also arsenical pyrites. It is a com mon constituent of other minerals, but in small quantities only. The arsenopyritc is the usual commercial ore from which arsenic is ob taMed. and the process for its reduction is by heating the ore in earthenware retorts or tubes laid horizontally in a long furnaee. As arsenic is quite volatile on heating, it condenses in the iron tube as a coherent crystalline mass, in which condition it may be detached from the tube the latter is unrolled. The arsenic thus obtained may be still further purified by a second sublimation.
Arsenic (symbol As, at. wgt. 73.01 ) is a steel-gray. brittle metal, with a specific gravity of 5.23 to 5.76; it is a good conductor of elec tricity, and is odorless and tasteless. It vola tilizes above 100' G., with a garlic-like odor, and is rapidly vaporized at a dull-red heat. It is used as a gonstituent of alloys, as white alloy, as speculum metal in bronzing brass, and in the manufacture of opal glass; also for hardening lead in the manufacture of shot. Arsenic and its soluble eompounds are exceedingly poisonous.
Arsenic forms two oxides—the arsenic tri oxide and the arsenic pentoxide. The former yields with basic radicals the salts called ar s•nites. It is commonly called orhile arsenic, arsenious acid, or flowers of arsenic, and is ob tained in various metallurgical processes by roasting arsenic ores, during which the vapors of the oxide are volatilized and subsequently condensed in receptacles called poison chambers, or poison towers. The crude oxide is purified by one or more •ublimations, yielding ultimately a white crystalline powder that is odorless, but has a weak. metallic. sweetish taste. It is the principal commercial compound of arsenic, and is used for the preparation of other arsenical compounds. in the production of green pig ments, in the manufacture of glass, and as a poison for rats and vermin; also in medicine, in various compounds snell as Fowler's solution, which is an arsenite of potassium. Arsenious oxide is used in medicine in treating many skin diseases, in anaemia, in chorea, in some forms of malarial fever, in cancer and other growths, in neuralgia, in asthma, and in certain gastric conditions. It is an alterative, and is frequently used in connection with other tissue builders or tonics during convalescence. Since small quantities produce poisoning, arsenic should be used only when prescribed by a physi cian. Chronie poisoning by this metal is not infrequent as it is nmeh used in the arts. re sulting in kidney disease and even paralysis. Vet it is asserted that in Styria the peasants consume arsenic daily—the women to improve their complexions, the men to increase their power of endurance. They are said to be strong
a-nd long-lived (see Edinburgh Medical and Surgical Journal, 1871, Vol. XVI., p. 569). Freshly precipitated hydrated oxide of iron, and the freshly precipitated hydrated oxide of iron with magnesia, are regarded as the best and most efficient antidotes for arsenious acid; hut immediate removal of the poison by vomiting or purging is desirable. For its detection, three methods are commonly employed. Of these, the first consists in the treatment of the material submitted for examination with a strong alkali. and passing through the filtered liquid a current of hydrogen disulphide, which, if arsenic be present, produces a precipitate of the yellow sulphide. The precipitate may he further tested by dissolving in al111110Dis and evaporating mail the residuary substance is reduced to metallic arsenic. Another method is the Reinsch pro cess, in which, the preparation containing arsenic having been brought into solution, newly bur nished pieces of copper foil are introduced into the liquid, and if arsenic be present it will at once be precipitated on the copper in its metallic form. It is said that by this method one part of arsenic can be detected in 250,000 parts of solution. A third, and perhaps the most useful, method is that invented by Marsh, which consists in treating the material with dilute sulphuric acid and metallic• zinc in a gas-generating apparatus. The arsenic combines with the hydrogen liberated by the zinc, and forms arseniuretted hydrogen, which is then passed through a glass tube; on heating, it breaks up, depositing metallic arsenic in the form of a 'mirror' near the open end of the tube. In carrying out this operation, especially in criminal cases, the utmost preesutions are neces sary to insure the perfect freedom of the ap paratus and reagents from arsenic or simi lar substances capable of producing an arsenic like 'mirror.' Among other things. the nature of the mirror may be demonstrated by dissolv ing it and testing the solution obtained by one of the usual methods. In order to detect arsenic in wall-papers or cotton fabrics, the Marsh test is usually employed—that is, the material is brought into solution, to which zinc and sul phuric acid are added, yielding the arseniurettcd hydrogen. It frequently happens that the ar senic is contained in the fabric itself. so that the test must not be made with the dissolved color alone, but with the entire material. With cop per oxide arsenious oxide forms a copper arscn itc which is a pigment known as Scheeir's green, largely used in calico printingandforwall-papers. With basic copper acetate it yields Schweinfu•th green—called also emerald green. imperial green, and mills green—which is a well-known pig ment frequently used in the manufacture of wall-paper.
When acted upon by oxidizing agents, arseni ous oxide yields arsenic oxide. which combines with basic radicals to form arsenates. Arsenic oxide, or arsenic acid, is used as an oxidizing agent in the preparation of aniline red, and also as a substitute for tartaric acid in calico printing.
Arsenic combines with sulphur, yielding an orange-yellow disulphide, which is found native as the mineral realgar and is used as a pigment and as a depilatory. A trisullMide also exists, which is found native as the mineral orpiment, is used in pyrote•hny and as a pigment for artists; also formerly in dyeing, and with quick-lime as a depilatory under the name of rumor.