Antimony is a compound, consisting of a semi-metallic part united with about a fourth part of its weight of common Sulphur. It appears, in the ninth column of the Table of Affinities, that all the metals, Mercury and Gold excepted, have a greater affinity than the reguline part of Antimony with Sulphur. If therefore Gold, adulterated with a mixture of Copper, Silver, or any other metal, be melted with Antimony, those metals will unite with the Sulphur of the Antimony, and separate it from the reguline part, which being thus set free will combine and be blended with the Gold. These two metallic substances, forming a mass far heavier than the other metals mixed with the sulphur, fall together to the bottom of the crucible in the form of a Regulus, while the others float over them like a sort of scoria or flag: and thus the Gold is freed from all alloy but the reguline part of the Antimony. As all the other metals have a great affinity with Sulphur, and Gold is the only one that is capable of resisting its action, one would think Sulphur alone might be sufficient to free it from the metals combined with it, and that it would therefore be better to employ pure Sulphur, in this operation, than to make use of Antimony; the reguline part of which remaining united with the Gold requires another long and laborious operation to get rid of it. Indeed, strictly speaking, Sulphur alone would be sufficient to produce the desired separation: but it is proper to observe, that, as Sulphur alone is very combustible, most of it would be consumed in the operation before it could have an opportunity to unite with the metallic substances; whereas, when it is combined with the Regulus of Antimony, it is thereby enabled to bear the action of the fire much longer without burning, and consequently is much fitter for the purpose in question. Besides, if we were to make use of pure Sulphur, a great part of the Gold, which is kept in perfect fusion, and its precipitation facilitated, by the Regulus of Antimony, would remain confounded with the Sulphureous scoria. Nevertheless, seeing the metals with which Gold is alloyed cannot be separated from it by Antimony, but that a quantity of Regulus proportioned to the quantity of the metals so separated will unite with the Gold, and that the more Regulus combines with the Gold, the more tedious, chargeable, and laborious will the operation prove, this consideration ought to have some influence in directing our process. Therefore, if the Gold be very impure, and worse than sixteen carats, we must not mix it with crude Antimony alone, but add two drams of pure Sulphur for every carat the Gold wants of sixteen, and lessen the quantity of Antimony in proportion to that of the real Gold. It is necessary to keep the crucible close covered, after mixing the Antimony with the Gold, to prevent any coals from falling into it: for, if that should happen, the melted mass would puff up considerably, and might perhaps run over.