Argentina, Potentilla, Anserina. Penta-phylloides argenteum alatum seu potentilla Town. Potentilla anserina Linn. Silverweed or wild tansy: a low creeping plant, with winged-leaves, composed of seven or eight pair of oblong indented segments set along a middle rib, with smaller portions between, green above, and covered with a silver-coloured down underneath; the flowers, which rife on long pedicles in the bosoms of the leaves, are composed, each, of five gold-coloured petals with a number of threads in the middle, and followed by a small cluster of naked seeds. It is perennial; common by the sides of rivulets and in moist uncultivated places; and flowers in June.

The leaves of argentina have been generally looked upon as strong astringents, and recommended as such in fluxes and haemorrhages.

That they have an astringent quality is manifest to the taste, and from their striking a black colour with solutions of chalybeate vitriol: but. in the leaves in substance, whether fresh or dry, and in their infusions, decoctions, and expressed juice, the preparations which have been generally made use of, the astringency is very weak; and even the extracts made from them, by water and by rectified spirit, in which all their active matter is concentrated, are only among the milder styptics or corroborants. The spiri-tuous extract is stronger than the watery, and in proportionably smaller quantity.

Argenhum Pharm. Lond. & Edinb. Silver: a white metal; becoming yellow, and at length black, from the vapour of sulphureous solutions and of putrefying matters; extremely malleable; near eleven times specifically heavier than water; fusible in a bright red heat; fixt and indestructible in the fire; soluble, in the nitrous acid, into a limpid liquor, which stains the solid parts of animals black; not soluble, by moderate digestion, in the marine or vitriolic acid; precipitable by these acids from its solution in the nitrous.

The greatest quantities of this metal are found in the mines of Chili and Peru; commonly in small grains and filaments, embedded in different earths and stones; from which it is separated by pulverization, ablution with water, and amalgamation with mercury. Several mines in England, Germany, and other parts of Europe, afford silver; rarely native, or in dis-tinguishable masses; commonly reduced to a state of ore, of a red, or of a yellow or brown, or of a dusky leaden or black colour, by an intimate admixture of arsenic, or sulphur, or both; from which it cannot be extracted by quicksilver, but which are dissipated by calcination, so as to leave the silver separable from the remaining earth by fusion.

Crude silver, however comminuted or attenuated, has not been observed to produce any medical effect; though abundance of virtues were ascribed to it by the credulity of former times. It is not soluble in any of the fluids of the animal or vegetable kingdom.

It dissolves, by the assistance of a moderate heat, in about twice its weight of pure aqua fortis: the solution, duly exhaled and set in the cold, crystallizes into thin colourless transparent plates. The crystals, or the dry matter left upon infpiffating the solution, melt in a moderate fire, and on cooling form a dark coloured caustic mass. This preparation is in common use for consuming warts and callosities; but is less fit for such purposes as require a considerable quantity to be applied, as the laying open of imposthumations, being apt to liquefy by the moisture of the skin, and spread beyond the limits in which it is intended to operate. For the greater conveniency of using, it is call into oblong (lender pieces, either in iron pipes heated and greased, or in holes made by some smooth instrument in a lump of tempered tobacco-pipe clay: each piece is wiped clean, and wrapt in dry soft paper. The matter is to be poured out as soon as it flows thin: if kept a little too long in fusion, it becomes too thick to run into the mould, and parts with lb much of its acid as not to be sufficiently corrosive: by a longer continuance of the fire, all the acid is gradually dissipated, and a lump of pure silver remains. Ph Lond.

Caufticum lunare Ph. Ed.

A preparation somewhat less caustic than the foregoing, is recommended internally by An-gelus Sala, Boyle, and others, as an anthelmintic, and as a purgative in hydropic and inveterate ulcerous diseases. For this purpose, the crystals of silver are dissolved in water, and mingled with a solution of equal their weight of nitre: this mixture is evaporated to dryness, and the residuum calcined with a gentle heat, just not sufficient to melt it, and kept continually stirring, till no more fumes arise. Boer-haave allures us, that two grains of this preparation, made into pills with crumb of bread and a little sugar, and taken on an empty stomach, some warm water sweetened with a little honey being drank immediately after, purge gently without griping, and bring away a large quantity of water almost without the patient's perceiving it. He nevertheless cautions against the too liberal or continued use of this medicine, and observes, that by its corrosive quality it weakens the bowels, particularly the stomach, and that therefore proper corroborants, as rob of juniper berries, ought to be interposed. Even with this assistance, however, it is at best a dangerous medicine, and as such deservedly stands excluded from practice.