Redness; Though I say such Instances might be Multiply'd, and though there
be some other Obvious changes of Colours, which happen so frequently, that
they cannot but be as well Considerable as Notorious; such as is the
Blackness of almost all Bodies burn'd in the open Air: yet our haste
invites us to resign you the Exercise of enquiring into the Causes of these
Changes. And certainly, the reason both _why_ the Soots of such differing
Bodies are almost all of them all Black, _why_ so much the greater part of
Vegetables should be rather Green than of any other Colour, and
particularly (which more directly concerns this place) _why_ gentle Heats
do so frequently in Chymical Operations produce rather a Redness than
another Colour in digested _Menstruums_, not only Sulphureous, as Spirit of
Wine, but Saline, as Spirit of Vinegar, may be very well worth a serious
Inquiry; which I shall therefore recommend to _Pyrophilus_ and his
Ingenious Friends.

[21] _Parkinson_, Thea. Bot. Trib. 4 cap. 12.

_EXPERIMENT XXXVII._

It may seem somewhat strange, that if you take the Crimson Solution of
_Cochineel_, or the Juice of Black Cherries, and of some other Vegetables
that afford the like Colour, (which because many take but for a deep Red,
we do with them sometimes call it so) and let some of it fall upon a piece
of Paper, a drop or two of an Acid Spirit, such as Spirit of Salt, or
_Aqua-fortis_, will immediately turn it into a fair Red. Whereas if you
make an Infusion of Brazil in fair Water, and drop a little Spirit of Salt
or _Aqua-fortis_ into it, that will destroy its Redness, and leave the
Liquor of a Yellow, (sometimes Pale) I might perhaps plausibly enough say
on this occasion, that if we consider the case a little more attentively,
we may take notice, that the action of the Acid Spirit seems in both cases,