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in spirit of salt, and precipitating again, it becomes, heflfys, extremely fair, and in this state he directs it to bemixed with a due proportion of Venice glass.

Hellot describes a preparation which in mixture withVenice glass was found to give a beautiful purpleenamel. Equal parts of solution of gold, and of solutionof zinc in aqua regia, are mixed together; and a volatilespirit, prepared from sal ammoniac by quicklime, addedto the mixture in sufficient quantity to precipitate the twometals. The precipitate is to be gradually heated, till itacquires a violet colour : it does not fulminate, makingonly a flight dull decrepitation without any of its particlesflying about.

Though a purple, or a red colour approaching to thatof the ruby, may by the foregoing means be baked uponglass or enamels, and introduced into the mass by fusion,the way of equally diffusing such a colour through a quan-tity of fluid glass is still a secret.

I was once, many years ago, fortunate enough to suc-ceed, at a glass-house, in a small pot of glass, of whicha salver was blown of a fine ruby red : the tinging mat-ter was the precipitate of gold by tin ; the particulars ofthe process cannot now be recollected. I have since triedthe remainder of the same preparation, with commonflint glass, with green glass, with various fritts composedof flint, borax, pure fixt alkaline salt, nitre, sal ammoniac.When flint was used, it was several times made red hot,and quenched in water, to render it more easily pulvera-ble : both the flint and glasses were powdered in an ironmortar, and the powders well washed with diluted oil ofvitriol, to extract such particles of iron as they mighthave worn off in the trituration ; the gold precipitate wasground with the other ingredients, in agate or glass mor-tars ; its proportion was varied from an eighth part to

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