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.
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