first.

_EXPERIMENT XLII._

That the Colour (_Pyrophilus_) of a Body may be chang'd by a Liquor which
of it self is of no Colour, provided it be Saline, we have already
manifested by a multitude of instances. Nor doth it seem so strange,
because Saline Particles swimming up and down in Liquors, have been by many
observ'd to be very operative in the Production and change of Colours. But
divers of our Friends that are not acquainted with Chymical Operations have
thought it very strange that a White Body, and a Dry one too, should
immediately acquire a rich new Colour upon the bare affusion of
Spring-Water destitute as well of adventitious Salt as of Tincture. And yet
(_Pyrophilus_) the way of producing such a change of Colours may be easily
enough lighted on by those that are conversant in the Solutions of Mercury.
For we have try'd, that though by Evaporating a Solution of Quick-Silver in
_Aqua-fortis_, and abstracting the Liquor till the remaining matter began
to be well, but not too strongly dryed, fair Water pour'd on the remaining
_Calx_ made it but somewhat Yellowish; yet when we took good Quick-Silver,
and three or four times its weight of Oyl of Vitriol, in case we in a Glass
Retort plac'd in Sand drew off the Saline _Menstruum_ from the Metalline
Liquor, till there remain'd a dry _Calx_ at the bottome, though this
Precipitate were a Snow White Body, yet upon pouring on it a large quantity
of fair Water, we did almost in a moment perceive it to pass from a Milky
Colour to one of the loveliest Light Yellows that ever we had beheld. Nor
is the Turbith Mineral, that Chymists extol for its power to Salivate, and
for other vertues, of a Colour much inferiour to this, though it be often
made with a differing proportion of the Ingredients, a more troublesome
way. For _Beguinus_,[22] who calls it _Mercurius praecipitatus optimus_,
takes to one part of Quick-Silver, but two of Liquor, and that is Rectifi'd
Oyl of Sulphur, which is (in _England_ at least) far more scarce and dear
than Oyl of Vitriol; he also requires a previous Digestion, two or three
Cohobations, and frequent Ablutions with hot Distill'd Water, with other
prescriptions, which though they may conduce to the Goodness of the
Medicine, which is that he aims at, are troublesome, and, our Tryals have
inform'd you unneccessary to the _obtaining the Lemmon Colour_ which he
regards not. But though we have very rarely seen either in Painters Shops,
or elsewhere a f