[ 6x9 ]

the salt remaining whitish. When the salt was melted ina crucible with equal its weight, or a thiru of its weight,of gold or aurutn fulminans, it received no purple or rosecolour, and did not appear to take up any part of the gold.Ground with gold leaf, and exposed to the focus of a burn-ing-glafs about a foot in diameter, it smoked, frothed,and flowed long, but at length the gold rose up to thesurface, leaving the fait clear. One part of the purple calxof gold, precipitated from aqua regia by tin, being mixedwith ten parts of the fait, and melted in a crucible with astrong fire; most of the fait rose over the crucible, leavinga brownish glass, and the gold revived into grains. Onepart of a calx of gold made with quicksilver, and ten ofthe fait, melted in a strong sire, gave likewise a yellow-brown glass, and the gold was found revived. One partof gold, two parts of sal ammoniac, and eight parts of themicrocofmic fait, being melted together, the fait run allthrough the crucible, the gold remaining in grains.

Solution of gold in aqua regis is precipitated by solutionof the microcofmic fait, provided the aqua regis is fullysaturated with the gold, and the microcofmic solutionadded in sufficient quantity. Is the mixture of the twosolutions be poured upon compositions for glass, the wholeboiled down to dryness, then well ground together, andbrought into fusion, the gold either wholly disappears, orhardly a footstep of it is to be seen. A composition ofthree parts of powdered flint, two parts of saltpetre, andone part of calcined borax, being treated in this mannerwith the mixt solutions; a blue landiver, almost like tur-cois, was found on the top of the melted matter, and apure blue glass underneath. With regard to the blue co-lour, which may seem pretty extraordinary, the authorobserves that some variation may happen from the degreeof fire, and that the common ruby glass, when in giving

L 1 1 1 it