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matter is to be washed two or three times with waterin the filter, and this liquor poured to the rest.

For recovering the gold from the solution, Cramerdirects two methods, distilling off the menstruum, andprecipitating the gold by mercury. But in either of theseways we cannot be certain of having the gold pure. Forthough it has been previously cupelled with lead, yet, ifit contained any platina, it will retain the whole of theplatina after the cupellation, and in some circumstances,as we have already seen, it will retain also a little copper :both the platina and copper will dissolve with it in aquaregia; mercury will precipitate the platina along with thegold j and the abstraction of the menstruum will leave withit both the platina and copper.

The purity of the gold is secured by precipitation withcommon green vitriol. The vitriol is to be dissolved incold water, the solution passed through a filter, and addedin large quantity to the solution of gold : the quantity ofvitriol, before its dissolution, should be ten or twelve timesgreater than that of the gold. As the precipitate fallsslowly, the mixture is to be set by for twenty four hoursor more : the liquor, then become clear, though of a deepcolour, is to be poured off; the brownish powder at thebottom, boiled in a little aqua fortis, then washed withwater, and melted with the addition of a little nitre.

Gold, thus purified, appears to be perfectly fine; apoint not obtainable by any other known means thatcan be practised in the way of business. Nor does theprocess seem to be so expensive as the imperfect one byaqua fortis; for there, three parts or more of silverbeing added to one of gold, at least six parts of aquafortis are required for dissolving the silver ; whereas thegold, in the above process, may be dissolved by half thatquantity of the menstruum: great part of the acid may like-wise