XV. Another way of rendring the Gold precipitated by the Liqour of Flints fusible.
Take of the said Gold one part, and the fixt Salt made of Salt Peter and Tartar, by combustion or calcination, three parts; commix them and melt them down in a crucible well covered. In this co-melting the Salt swallows up the Flints, and the Gold being at liberty settles to the bottom. Pour out the molten mass, and separate the Regulus of the Gold from the Salt, the which being dissolved with common water gives you your Liqour of Flints, to be again used to precipitate more extracted Gold.
This Salt doth not so easily perforate the Crucibles as those Glasses of Lead do, and therefore is it to be accounted of as the best and easiest of all these three prescribed ways.
XVI. The way of reducing Gold, precipitated by the spirit of Urine.
The spirit of Urine or of Sal. Armoniack doth perfectly precipitate all the Gold out of the Aq. Regis; the which being washed and dried, doth not admit of reduction after the manner of the other Gold, for if it be but onely heated a little before it becomes red hot, it presently takes fire, and fulminates with a far more dreadfull noise than any Gunpowder. For if you put a small portion of the same, and no bigger than a Pea in a Silver, Iron, or Copper Spoon, and put it on the Coals that it may wax hot, it will give such an horrible crack, that ’twill even dull the hearing, and make a dent in the Spoon as if it had been beaten in with a Hammer. From whence it may easily be conjectured, that if somewhat a bigger quantity be put in a Pot on the Fire, it would make Pot and Furnace flie, by its so dreadfull thundring a stroak into most small shivers.
So then there is need of great wariness, to prevent the happening of so great danger, which is easily prevented by the following manner of operating.
XVII. By what means the fulminating force of Gold precipitated by a Lixivium, or spirit of Urine is to be taken away.
Mix with this Gold precipitated by a Lixivium, or by the spirit of Urine, half a part of Sulphur reduced into Powder, and let the said Sulphur be removed therefrom by burning amidst live Coals; for so being despoiled of that fulminating force, it may without danger be reduced by any kind of such matters as promote fusibility.
XVIII. By what means Gold that is despoiled of its fulminating force, by means of Sulphur may be reduced.
Forasmuch as this Gold is void of all impurity, there needs [not] the addition of such matters as promote fusion, seeing it is of it self prone enough to melt. But yet least some grains of the Gold should stick on to the Pot, ’tis expedient to add some portion at least of such a kind of matter as accelerates or hasteneth fusion. And for this work, Borax, and the dry Liqour of Flints are excellent, of which if you add but one half part onely to such Gold, (or, if you take of the Flints prepared with Salt of Tartar) it will by that means presently melt, and the Borax, or Liqour of Flints will not retain the least doit of the Gold.