Lead being Calcin'd
with a Strong fire turns (after having purhaps run thorough divers other
Colour) into _Minium_, whose Colour we know is a deep red; and if you urge
this _Minium_, as I have purposely done with a Strong fire, you may much
easier find a Glassie and Brittle Body darker than _Minium_, than any white
_Calx_ or Glass. 'Tis known among Chymists, that the white _Calx_ of
Antimony, by the further and more vehement operation of the fire, may be
melted into Glass, which we have obtain'd of a Red Colour, which is far
deeper than that of the _Calx_ of Burnt Antimony, and though common Glafs
of Antimony being usually Adulterated with _Borax_, have its Colour thereby
diluted, oftentimes to a very pale Yellow; yet not onely ours made more
sincerily, was, as we said, of a Colour less remote from Black, than was
the _Calx_; but we observ'd, that by Melting it once or twice more, and so
exposing it to the further operation of the Fire, we had, as we expected,
the Colour heightned. To which we shall add but this one Instance, (which
is worth the taking notice of in Reference to Colours:) That, if you take
Blew, but Unsophisticated, Vitriol, and burn it very slowly, and with a
Gentle degree of Heat, you may observe, that when it has Burnt but a
Little, and yet so far as that you may rub it to Powder betwixt your
fingers, it will be of a White or Whitish Colour; But if you Prosecute the
Calcination, this Body which by a light Adustion was made White, will pass
through other Colours, as Gray, Yellowish, and Red; and if you further burn
it with a Long and Vehement fire, by that time it comes to be _Perustum_,
it will be of a dark purple, nearer to Black, not only than the first
_Calx_, but than the Vitriol before it at all felt the fire.
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