by Nature or by Art; For in factitious Sal Armoniack we finde the common and the Urinous Salts so well mingled, that both in the open Fire, and in subliming Vessels they rise together as one Salt, which seems in such Vessels irresoluble by Fire alone. For I can shew you Sal Armoniack which after the ninth Sublimation does still retain its compounded Nature. And indeed I scarce know any one Mineral, from which by Fire alone Chymists are wont to sever any Substance simple enough to deserve the name of an Element or Principle. For though out of native Cinnaber they distill Quicksilver, and though from many of those Stones that the Ancients called Pyrites they sublime Brimstone, yet both that Quicksilver and this Sulphur being very often the same with the common Minerals that are sold in the Shops under those names, are themselves too much compounded Bodies to pass for the Elements of such. And thus much, Eleutherius, for the Second Argument that belongs to my First Consideration; the others I shall the lesse insist on, because I have dwelt so long upon this.
Proceed we then in the next place to consider, That there are divers Separations to be made by other means, which either cannot at all, or else cannot so well be made by the Fire alone. When Gold and Silver are melted into one Mass, it would lay a great Obligation upon Refiners and Goldsmiths to teach them the Art of separating them by the Fire, without the trouble and charge they are fain to be at to sever them. Whereas they may be very easily parted by the Affusion of Spirit of Nitre or Aqua fortis (which the French therefore call Eau de Depart:) so likewise the Metalline part of Vitriol will not be so easily and conveniently separated from the Saline part even by a violent Fire, as by the Affusion of certain Alkalizate Salts in a liquid Form upon the Solution of Vitriol made in common water. For thereby the acid Salt of the Vitriol, leaving the Copper it had corroded to joyn with the added Salts, the Metalline part will be precipitated to the bottom almost like Mud. And that I may not give Instances only in De-compound Bodies, I will