Minerals alſo by the Action of the Fire may be brought to afford Colours 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 elſewhere note, does very eaſily of it ſelf acquire the conſiſtence, not of a Metalline Calx, but of a Coagulated matter, which we have obſerv'd with pleaſure to look ſo like, either to curdled Milk, or curdled Whites of Eggs, that a perſon unacquainted with ſuch Solutions may eaſily be miſtaken in it. But when I purpoſely prepar'd a Menſtruum that would diſſolve it as Aqua-fortis diſſolves Silver, and not barely Corrode it, and quickly let it fall again, I remember not that I took notice of any particular Colour in the Solution, as if the more Whitiſh Metalls did not much Tinge their Menſtruums, though the conſpicuouſly Colour'd Metalls as Gold, and Copper, do. For Lead diſſolv'd in Spirit of Vinegar or Aqua-fortis gives a Solution cleer enough, and if the Menſtruum be abſtracted appears either Diaphanous or White. Of the Colour of Iron we have elſewhere ſaid ſomething: And 'tis worth
noting, that though if that Metall be diſſolv'd in oyl of Vitriol diluted with water, it affords a Salt or Magiſtery ſo like in colour, as well as ſome other Qualities, to other green Vitriol, that Chymiſts do not improperly call it Vitriolum Martis; yet I have purpoſely try'd, that, by changing the Menſtruum, and pouring upon the filings of Steel, inſtead of oyl of Vitriol, Aqua Fortis, (whereof as I remember, I us'd 4 parts to one of the Metall) I obtain'd not a Green, but a Saffron Colour Solution; or rather a thick Liquor of a deep but yellowiſh Red. Common Silver, ſuch as is to be met with in Coines, being diſſolv'd in Aqua fortis, yields a Solution tincted like that of Copper, which is not to be wondred at, becauſe in the coining of Silver, they are wont (as we elſewhere particularly inform you) to give it an Allay of Copper, and that which is ſold in ſhops for refined ſilver, is not (ſo far as we have tryed) ſo perfectly free from that ignobler Metall, but that a Solution of It in 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