salep; from the tubers of tacca oceanica.
Rio, or Manihot Arrow Root. Scale 1-1000th of an inch.
ARSE′′NIATE. Syn. Ar′senate; Arse′′nias, Ar′senas, L.; Arséniate, Fr.; Arse′′niksaure salze, Ger. A salt consisting of AsO4 and a metal or other basic radical; e.g., ammonio-magnesium arseniate, NH4Mg9AsO4.
AR′SENIC (-se-nĭk). As. Syn. Arsenium; Arsen′icum, Arse′nium, L.; Arsenik, A.-metall, Ger. Arsenico, Sp., It. The brittle, grey-coloured metal, or metalloid, which forms the base of the white arsenic and orpiment of commerce. Discovered by Geber in the eighth century, but first accurately described by Brandt (A.D. 1773). The poisonous properties of arsenious acid were not generally known for some centuries after its discovery. As a medicine it was first employed in intermittents in Hungary.
Sources. Arsenic is peculiar to the mineral kingdom. The metallic arsenic of commerce is obtained by roasting arsenical pyrites (MISPICKEL), in earthen tubes, or in tubular earthen retorts; the arsenic sublimes, and sulphuret of iron remains behind. On the small scale it is prepared by sublimation from a mixture of arsenious acid and charcoal or black flux. Combined with oxygen it frequently exists in mineral waters; and, in a larger quantity, in certain rivulets and streams.
Prep. A mixture of arsenious acid, 1 part; and black flux, 2 or 3 parts; is exposed to a low red heat in a Hessian crucible over which is luted a deep empty crucible, or an earthen tube, to receive the metal; the latter being kept as cool as possible. Charcoal or even oil may be substituted for black flux, and a retort of hard glass may be used, with the same result. Or the following method may be used:—White oxide of arsenic, of commerce, 2 dr.; is placed at the sealed end of a hard German-glass tube (1⁄2 × 18 inches), and covered with about 8 inches of dry and coarsely powdered charcoal; the portion of the tube containing the latter is then raised to a red heat, whilst a few ignited coals are placed beneath the oxide to effect its slow sublimation. The sublimed metal gradually attaches itself to the inside of the tube at its cool extremity. A small charcoal furnace similar to that used for organic analysis should be employed, and the process conducted under a flue to carry off any fumes that may escape. The open end of the tube should be loosely closed with a cork.
Prop. Very brittle, so much so that it may be easily powdered in a mortar; lustre highly metallic; colour steel-grey or bluish-white; texture crystalline; crystals rhombohedrons; sublimes, without fusion, at 356 to 360° Fahr., (and slowly at lower temperatures), in close vessels unaltered, but when exposed to the air with conversion into arsenious acid; at a higher temperature, in open vessels, it burns with a pale-blue flame. Its vapour or fumes have a characteristic alliaceous odour; it is slowly oxidised and dissolved by boiling water; but may be preserved unchanged in pure cold water; it rapidly tarnishes in the air, particularly when moist, a black film, consisting of metallic arsenic and arsenious acid forming on its surface; with chlorine, iodine, sulphur, and hydrogen, it unites to form definite compounds. With oxygen it forms acids, but no basic oxide. It combines with the metals in a similar manner to sulphur and phosphorus, the latter of which it resembles in many respects. These compounds are termed AR′SENIDES, formerly Arseniurets. Sp. gr. 5·7 to 5·9; sp. gr. of vapour, 1·0362.
Uses, &c. With copper it forms a white alloy (PACKFONG); and it is added to some other alloys to increase their whiteness, hardness, and fusibility. In medicine it is only used in combination. In the metallic state it is inert; but, from its great affinity for oxygen, it rapidly becomes oxidised and poisonous; and hence acts as a powerful poison when swallowed, or when rubbed on the skin. Its fumes are also highly poisonous. See Arsenious Acid (and below).
Arsenic, Tribro′mide of. AsBr3. Syn. Terbro′mide of arsenic, Sesquibro′mide of a.; Arsen′ici Bromi′dum, L. Prep. Add metallic arsenic, in powder, cautiously and in a very small quantity at a time, to pure bromine, contained in a vessel set in ice or a freezing mixture, until light ceases to be emitted; then cautiously distil into a well-cooled receiver.