Pure sulphur hath no effect on Gold; but being combined with an alkali into a _hepar sulphuris_, it unites therewith very readily. Nay, so intimate is their union, that the Gold, by means thereof, becomes soluble in water; and this new compound of Gold and liver of sulphur, being dissolved in water, will pass through the pores of brown paper without suffering any decomposition; which does not happen, at least in such a manifest degree, to other metallic substances dissolved by liver of sulphur. _Aurum fulminans_, mixed and melted with flower of sulphur, loses its fulminating quality: which arises from hence, that on this occasion the sulphur burns, and its acid, which is the same with the vitriolic, being thereby set at liberty becomes capable of acting upon the Gold as a vitriolic acid would; which, as was said above, deprives the Gold of its fulminating quality. SECTION II. _Of_ SILVER. Next to Gold, Silver is the most perfect metal. Like Gold it resists the utmost violence of fire, even that in the focus of a burning-glass. However, it holds only the second place among metals; because it is lighter than Gold by almost one half; is also somewhat less ductile; and, lastly, because it is acted upon by a greater number of solvents. Yet Silver hath one advantage over gold, namely that of being a little harder; which makes it also more sonorous. This metal, like Gold, begins to flow when it is so thoroughly penetrated by the fire as to appear ignited like a live coal. While this metal is in fusion, the immediate contact of the vapour of burning coals deprives it almost entirely of its malleability, in the same manner as we observed happens to Gold: but both these metals easily recover that property by being melted with nitre. The nitrous acid is the true solvent of Silver, and being somewhat dephlegmated will very readily and easily take up a quantity of Silver equal in weight to itself. Silver thus combined with the nitrous acid forms a metallic salt which shoots into crystals, called by the name of _Lunar Crystals_, or _Crystals of Silver_. These crystals are most violently caustic: applied to the skin they quickly affect it much as a live coal would; they produce a blackish eschar, corroding and entirely destroying the parts they touch. Surgeons use them to eat away the proud fungous flesh of ulcers. As Silver united with the nitrous acid hath the property of blackening all animal substances, a solution of this metallic salt is employed to dye hair, or other animal matters, of a beautiful and durable black. These crystals flow with a very moderate heat, and even before they grow red. Being thus melted they form a blackish mass; and in this form they are used by Surgeons, under the title of _Lapis Infernalis_, _Infernal Stone_, or _Lunar Caustic._