Chymists are
pleas'd to call, how properly I have elsewhere examin'd, the _Sulphur of
Vitriol_. So that most part of Dissolv'd Bodyes being by Praecipitation
brought to White Powders, and yet some affording Praecipitates of other
Colours, the reason of both the Phaenomena may deserve to be enquir'd into.

_EXPERIMENT XIII._

Some Learned Modern Writers[15] are of Opinion, that the Account upon which
Whiteness and Blackness ought to be call'd, as they commonly are, the two
Extreme Colours, is, That Blackness (by which I presume is meant the Bodyes
endow'd with it) receives no other Colours; but Whiteness very easily
receives them all; whence some of them compare Whiteness to the
_Aristotelian Materia prima_, that being capable of any sort of Forms, as
they suppose White Bodyes to be of every kind of Colour. But not to Dispute
about Names or Expressions, the thing it self that is affirm'd as Matter of
Fact, seems to be True enough in most Cases, not in all, or so, as to hold
Universally. For though it be a common observation among Dyers, That
Clothes, which have once been throughly imbu'd with Black, cannot so well
afterwards be Dy'd into Lighter Colours, the praeexistent Dark Colour
infecting the Ingredients, that carry the Lighter Colour to be introduc'd,
and making it degenerate into Some more Sad one; Yet the Experiments lately
mention'd may shew us, that where the change of Colour in Black Bodies is
attempted, not by mingling Bodyes of Lighter Colours with them, but by
Addition of such things as are proper to alter the Texture of those
Corpuscles that contain the Black Colour, 'tis no such difficult matter, as
the lately mention'd Learned Men imagine, to alter the Colour of Black
Bodyes. For we saw that Inks of several Kinds might in a trice be depriv'd
of all their Blackness; and those made with Logwood and Red-Roses might
also be chang'd, the one into a Red, the other into a Reddish Liquor; and
with Oyl of _Vitriol_ I have sometimes turn'd Black pieces of Silk into a
kind of Yellow, and though the Taffaty were thereby made Rotten, yet the
spoyling of that does no way prejudice the Experiment, the change of Black
Silk into Yellow, being never the less True, because the Yellow Silk is the
less good. And as for Whiteness, I think the general affirmation of its
being so easily Destroy'd or Transmuted by any other Colour, ought not to
be receiv'd without some Cautions and Restrictions. For whereas, according
to what I