very differing from their own, as I not long since noted to you about the
variously Colour'd Flowers of Antimony, to which we may add the Whitish
Grey-Colour of its _Calx_, and the Yellow or Reddish Colour of the Glass,
where into that _Calx_ may be flux'd.

And I remember, that I elsewhere told you, that Vitriol Calcin'd with a
very gentle heat, and afterwards with higher and higher degrees of it, may
be made to pass through several Colours before it descends to a Dark
Purplish Colour, whereto a strong fire is wont at length to reduce it. But
to insist on the Colours produc'd by the Operation of fire upon several
Minerals would take up farr more time than I have now to spare.

_EXPERIMENT XLVII._

The Adventitious Colours produc'd upon Metalls, or rather with them, by
Saline Liquors, are many of them so well known to Chymists, that I would
not here mention them, but that besides a not un-needed Testimony, I can
add something of my own, to what I shall repeat about them, and divers
Experiments which are familiar to Chymists, are as yet unknown to the
greatest part of Ingenious Men.

That Gold dissolv'd in _Aqua Regia_ ennobles the _Menstruum_ with its own
Colour, is a thing that you cannot (_Pyrophilus_,) but have often seen. The
Solutions of Mercury in _Aqua-fortis_ are not generally taken notice of, to
give any notable Tincture to the _Menstruum_; but sometimes when the Liquor
first falls upon the Quick Silver, I have observ'd a very remarkable,
though not durable, Greenness, or Blewness to be produc'd, which is a
_Phænomenon_ not unfit for you to consider, though I have not now the
leisure to discourse upon it. Tin Corroded by _Aqua-fortis_ till the
_Menstruum_ will work no farther on it, becomes exceeding White, but as we