Syn. Arsenic (F.), Arsenick (G.), Arsenico (S.).

This metal is found in most parts of the world, accompanying other metals, and occasionally uncombined, forming distinct and peculiar veins. The following are the states in which arsenic is found : -

1 Vide Nouv. Elemens de Therapeutique, par I. L. Alibert, 2d edit. vol. i. p. 141.

2 The Savoyards, and the inhabitants of the Vosges, both snuff and smoke the leaves; and thence the plant is known on the Continent by the name of Tabac des Savoyards et des Vosges. With the exception of the goat, no animal will eat the plant.

3 From of the other Greeks.

Dioscoridis, which, however, is not the metal, but realgar, one of the species of the sulphuret;

As metallic arsenic is not used in the arts, it is seldom extracted from its ores, but is prepared for the purposes of experiment or of curiosity from white arsenic, or arsenious acid, which is commonly procured in roasting the arseniate of cobalt. It is necessary, however, to be acquainted with the appearances and properties of metallic arsenic; as the reduction of the acid is one mode of ascertaining whether the arsenious acid has been used as a poison, in cases of suspicious death.

Its colour is bluish grey, something like that of steel, with much brilliancy. It is quickly tarnished by exposure to the air,' becomes black, and falls into powder. It is extremely brittle, and pulverulent. Its specific gravity is 5.8843.1 It volatilizes at a heat of 356° Fahrenheit, in dense white fumes, which have the odour of garlic, although the solid metal is inodorous. In its metallic state, Arsenic exerts no action on the animal system; but when oxidized, it is a virulent poison. The equivalent of Arsenic is 37.7. Officinal. Acidum Arseniosum, Lond. Oxidum Arsenici,

Edin. Arsenici (oxydum album), Dub. White Arsenic.

Syn. Arsenic oxyde natif (F.), Naturlicoer Arsenickbalk (G.), Arsenik (Dan. Swed. Polish), Muschjak (Russian), Arsenico iixneo (I), Arsenico Turabulhalik (Arab.), Samuel-k'har (H.), Sanc'hya (San.), Vallay Paskanum ( Tarn.), Sumulfar (Fers.), Wrangon (Malay).

Arsenious acid is found native and uncombined at Andreas-burg in the Harz, and elsewhere: but the greater part of the white Arsenic (Arsenious acid) of commerce is obtained in Bohemia and Saxony, in roasting the Arseniurets of Cobalt for making zaffre; at Altenburg in Silesia it is procured from arsenical pyrites; and at Riechenstein from the sesquiarseniate

1 Turner. p 4 of iron. The roasting is performed in furnaces with long flues, in which the impure oxide is condensed, and this is purified by sublimation in the following method: - Large square boxes of cast-iron, furnished with conical heads, which are closely luted to them with clay, are disposed in a brick area, heated by the flues of two furnaces placed a little beneath them. When these boxes are red-hot, the impure arsenic, by fifteen pounds at a time, is put into them, where it melts and soon sublimes in the conical head. Successive additions are thus submitted to the action of heat, till about 150 pounds have been used to each vessel; and then the apparatus is allowed to cool. The conical head is now separated from the box, and carried with its contents into another place, where the workmen break off with hammers the sublimed oxide, separating the impurities for a second operation.1

The arsenious acid thus obtained is a dense, semi-transparent, or vitreous solid cake, breaking with a conchoidal fracture; and becoming opaque, of a snowy whiteness, and often pulverulent, when exposed to the air. It is met with in both these forms in the shops; and often is sold in powder, in which state it is sometimes adulterated with white sand, chalk, and gypsum; but the fraud is easily detected by heating a small portion of the suspected powder, by which the oxide is entirely dissipated, and the impurities are left behind.

A great quantity of the arsenious acid used in this country is brought from Germany, in casks, each containing from two to five hundred weight: much, however, is prepared in Cornwall2 from the arsenical ores of copper, in the roasting of which it is formed, and sublimes in a pulverulent form in chambers attached to the furnaces; after which it is refined in cast-iron pots with cylindrical heads, contracted into cones terminating in pipes. It sublimes, and is condensed in cakes in these heads.

Qualities.-Arsenious acid is inodorous; has very little taste, leaving on the tongue a sweetish impression; it is highly corrosive. When pure, if it have not been freely exposed to the action of the air, it is in semi-transparent, vitreous, colourless, shining masses, which break with a conchoidal fracture. Guibourt has lately ascertained that 1000 parts of water at 60° dissolve, during 36 hours, 9.6 of the glassy acid (sp. gr. 3.7391), and 12.5 of the opaque (sp. gr. 3.695): that the same quantity of boiling water dissolves 97 of the glassy, retaining 18 when cold; and 115 of the opaque, retaining 29 when cold. According to Dr. Christison, tea, milk, and similar organic substances impair its solubility.1 Both solutions usually slightly redden infusion of litmus, and combine with the alkalies. It is soluble also in solution of pure potassa, in alcohol, and in oils. When heated in the open air, this acid is volatilized in a temperature of about 380° Fahr.: the vapour has no odour; but if it be heated in contact with any substance which has an affinity for oxygen sufficient to decompose it, the vapours have an alliaceous odour.2 The specific gravity of the acid in its ordinary state is 3.706, that of the glassy variety 3.699. According to the average of the experiments by different chymists, 100 parts of the oxide consist of 74 6 of arsenic, and 25.4 of oxygen 3, or of 1 equiv. of arsenic = 37.7 + 1 1/2 of oxygen = 12; thence the equivalent of the acid is 49.7, or, according to Berzelius, of 2 As + 30= 99.4 (As). On the simple watery solution of the acid, no change is produced by a solution of sulphate of iron, of bichloride of mercury, tartar emetic, the mineral acids, or the alkalies; but ammoniacal nitrate of silver throws down a yellowish precipitate, which gradually passes to a brown colour; ammoniated sulphate of copper a pea-green precipitate; and acetate of lead a white precipitate.

Lime water also precipitates it white; sulphurets of the alkalies, pale yellow; and sulphuretted hydrogen gas, and an aqueous solution of that gas, golden yellow.

1 Journal de Physique, torn. i. p. 44.

2 There are only two works in Cornwall; one at the Cavan stream-works, the other at Perran near Truro.