Aqua styptica Ph. Ed.

In still smaler doses, the blue vitriol has been much used by some as a tonic in intermittent, and other diseases.

3. Vitriolum viride Pharm. Lond. Vitri-olum viride, five ferri Pharm. Edinb. Green vitriol, or vitriol of iron; commonly called English vitriol or copperas; the Roman vitriol of the Italian writers. This sort of vitriol is produced from sulphureo-ferrugineous pyritse, as the blue from sulphureo-cupreous ones; and as the ferrugineous minerals are much easier of resolution than the others, the ferrugineous vitriol is much oftener found native. In this native state, neither sort is free from an admixture of the other; the native green vitriols having always more or less of a bluish caft, and the blue of a greenish. The common green vitriol is prepared in large quantity at Deptford and Blackwall near London, and at Newcastle, by boiling iron with the acid liquor, which runs from certain pyritae after long exposure to the air: this vitriol appears to be purely martial, for if it should receive any cupreous particles from the mineral, the Superadded iron would precipitate them. All vitriols may be freed perfectly from copper by adding iron to solutions of them: those, which contain even a small portion of that metal, readily discover it by staining the iron of a copper hue.

Pure vitriol of iron is considerably transparent, of a fine bright, though not very deep, grass green colour; of a nauseous astringent taste accompanied with a kind of sweetishness. Dis-solved, and set to cryslallize, it (hoots into thick rhomboidal masses; a part generally rising at; the same time in efflorescences about the sides of the vessel. The solution deposites in standing a considerable quantity, and in boiling a much larger one, of the metallic basis of the vitriol, in form of a rusty calx or ochre: iron seems to be the only metallic body that thus separates spontaneously, in any considerable quantity, from the vitriolic acid. On exposing the vitriol itself to a moist air, a similar resolution happens on its surface; which, sooner or later, according as the acid is more or less saturated with the metal, changes its green to a rusty hue. In a warm dry air, it loses a part of the phlegm or water necessary to its crystalline form, and falls by degrees into a white powder. Exposed to a gentle fire, it liquefies and boils up; but soon changes, on the exhalation of the watery part that rendered it fluid, to a solid, opake, whitish or grey mass;, this, pulverized and urged with a stronger fire, continues to emit fumes, becomes yellow †, afterwards red, and at length, having parted with most of its acid as well as its phlegm, turns to a deep purplish-red calx ‡, revivable by inflammable substances into iron.

Pure green vitriol is in no respect different from the artificial fal martis. It is one of the most certain of the chalybeate medicines, scarcely ever failing to take effect: where the calces and other indissoluble preparations pass inactive through the intestinal tube. It may be conveniently given in a liquid form, largely diluted with aqueous fluids: two or three grains or more, dissolved in a pint or a quart of water (which from this quantity receives no disagree-able taste) may be taken in a day, divided into different doses. This vitriol is used also, espe-cially when calcined, as an external styptic: the styptic of Helvetius, and as is said that of Eaton, is no other than French brandy very slightly impregnated with the calcined vitriol: a dram of the vitriol is commonly directed to a quart of the spirit, but only a minute portion of the dram dissolves in it. As French brandy has generally an astringent impregnation from the oaken casks in which it has been kept, the vitriol changes it, as it does the watery infusions of vegetable astringents, to a black colour; but makes no such change in spirituous liquors that have not received some astringent tincture.

† Vitriolum calcinatum Pb Ed.

‡ Colcothar vitrioli Ph. Ed.

Chalcitis sac-titia Ph.Panis.

It is from the green vitriol that the acid called vitriolic has been generally extracted; by distilling the calcined vitriol in earthen long-necks, with a strong fire continued for two days or longer. The distilled spirit appears of a dark blackish colour; and contains a quantity of phlegm, greater or less according as the vitriol has been less or more calcined. On committing it a second time to distillation, in a glass retort placed in a sand-heat, the phlegmatic parts rife first, together with a portion of the acid, and are kept apart under the name of spirit or weak spirit of vitriol †: at the same time the remaining strong spirit, or oil as it is called, loses its black colour and becomes clear ‡, and this is the usual mark for discontinuing the rectification. The colleges of London and Edinburgh now directs a weak vitriolic acid of more certain strength, made by mixing one part of the strong acid with seven or eight parts of water ||.

The strong acid or oil of vitriol is the most ponderous of unmetallic fluids, and the most fixed of saline ones, yielding no smell in the greatest heat of the atmosphere, and requiring, to make it boil or distil, a heat considerably greater than that in which lead melts. Exposed to the air, it imbibes its humidity, so as to gain by degrees an increase of about twice its own weight. Mixed directly with water, it produces a heat so great as to render the vessel insupport-able to the hand: glass vessels are apt to crack from the suddenness of the heat, unless the commixture is very slowly performed. The most ready method of distinguishing it, in a dilute state, or when mixed with other acids, is by adding a solution of some calcareous earth, as chalk, made in any kind of acid liquor: this solution is by a minute portion of the vitriolic acid rendered milky, but suffers no change from any other species of acid; see Selenites.