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mixt covered with powdered charcoal, which, so far as itreaches, prevents the above change of the zinc.

The dissipation of regulus of antimony from gold re-quires, on the contrary, not only an open vessel and freeaccess of air, but the artificial impulse of a blast of air uponthe surface : if the fire is vehement, the crucible ssiallow,and the air strongly impelled, the gold is volatilized bythis metal more considerably than by either zinc or ar-senic ; but with proper care, the regulus may be blownoff without any sensible loss of the gold. Some have pro-posed regulus of antimony instead of mercury for gildingon copper; as also on earthen ware and glass, on which themercurial gilding cannot be applied : the regulus andgold, first melted together, are directed to be ground intofine powder, which being spread upon the piece, the wholeis exposed to a strong red heat, so as to evaporate theregulus. The inconveniencies of this method are, thatthe powder does not of itself adhere to the subject, andcan scarce be equably spread, and that part of the gold iswasted : that glass melts in the heat necessary for theexhalation of regulus of antimony, and that copper isliable to be corroded by the regulus, and have its surfacerendered uneven.

The base metals in general, which calcine or change toan earthy form in the fire, suffer the fame change whenmixed with gold, though with some differences in thedegree of facility. If gold, mixt with a small proportionof these metals, be kept for a considerable time in fusion,the base metal, gradually scorifying, rises to the surface,no longer miscible with the gold. If the gold is in lessquantity, and. the fire insufficient to bring the mass intofusion, the whole mixt loses by degrees its metallic aspect,and the gold remains intermingled among the calx of thebase metal, in a more attenuated state than it can perhaps

i be