_Aqua fortis_, will give a Venereal Tincture to the _Menstruum_. But we could not observe upon the solution of some Silver, which was perfectly refin'd, (such as some that we have, from which 8 or 10 times its weight of Lead has been blown off) that the _Menstruum_ though held against the Light in a Crystal Vial did manifestly disclose any Tincture, only it seem'd sometimes not to be quite destitute of a little, but very faint Blewishness. But here I must take notice, that of all the Metalls, there is not any which doth so easily and constantly disclose its unobvious colour as Copper doth. For not only in acid _Menstruums_ as _Aqua Fortis_ and Spirit of Vinegar, it gives a Blewish green solution, but if it be almost any way corroded, it _appears of one of those_ two colours, as may be observ'd in Verdigreese made several wayes, in that odd preparation of _Venus_, which we elsewhere teach you to make with Sublimate, and in the common Vitriols of _Venus_ deliver'd by Chymists; and so constant is the disposition of Copper, notwithstanding the disguise Artists put upon it, to disclose the colour we have been mentioning, that we have by forcing it up with _Sal Armoniack_ obtain'd a Sublimate of a Blewish Colour. Nay a famous Spagyrist affirms, that the very Mercury of it is green, but till he teach us an intelligible way of making such a Mercury, we must content ourselves to inform you, that we have had a Cupreous Body, that was Præcipitated out of a distill'd Liquor, that seem'd to be the the Sulphur of _Venus_, and seem'd even when flaming, of a Greenish Colour. And indeed Copper is a Metall so easily wrought upon by Liquors of several kinds, that I should tell you, I know not any Mineral, that will concurr to the production of such a variety of Colours as Copper dissol'd in several _Menstruums_, as Spirit of Vinegar, _Aqua fortis_, _Aqua Regis_, Spirit of Nitre, of Urine, of Soot, Oyls of several kinds, and I know not how many other Liquors, if the variety of somewhat differing colours (that Copper will be made to assume, as it is wrought upon by several Liquors) were not comprehended within the Limits of Greenish Blew, or Blewish Green.