Silver, one of the whitest of the perfect metals, is found in various parts of the globe, both in a native state, and alloyed with other ores.
The purest silver is imported by the Spaniards, from Potosi, in South America; and, though the lead-mines of England contain a portion of this valuable ore, yet it is so inconsiderable as not to defray the expence of separating it from lead.
In point of malleability, silver is somewhat inferior to gold ; but it is much harder than the latter. If, however, both metals be melted together, they readily combine, without materially diminishing their ductility : hence, such alloy is generally employed for gold coinage.
Silver acquires hardness by hammering, and is therefore (when alloyed with a certain proportion of copper), not only used for coining money, but likewise in the ma-nufacture of spoons, goblets, and other articles of plate, - Being, however, acted upon, in a peculiar manner, by sulphureous vapours, the surface of silver, if exposed to the air, easily becomes tarnished, and assumes a dark-brown colour. Various powders have, therefore, been contrived, with a view to restore plate to its original lustre; but, as most of these compounds are apt to scratch, and injure the substance of such expensive utensils, we recommend the following preparation : Take one ounce of red calx of vitriol (crocus martis) and two ounces of calcined chalk; let both ingredients be pulverized, and passed through the finest sieve. This composition may be applied, either in a dry state, or, if the silver be unusually tarnished, the powder may previously be moistened with spirit of wine, in order to produce the desired effect with greater expedition.
This precious metal is, likewise, advantageously employed in pharmacy. When dissolved in the nitric acid, it forms the nitrate of silver; and, though a most virulent medicine, it has been given with great success, to persons subject to epileptic fits ; in doses of a quarter of a grain, taken three times in the course of the day. It is farther useful externally, as a caustic, for consuming warts, and similar excrescences, not less than for preventing the growth of fungous flesh in ulcers ; but, in all these cases, it ought, on account of its deleterious qualities, to be directed by the profession.