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Boyle, Robert, 1627-1691

"Experiments and Considerations Touching Colours (1664)"

because the Saline principle does chiefly abound in
them, though indeed they be, as we elsewhere declare, mix'd Bodies, and
have most of them, besides what is Saline, both Sulphureous, Aqueous, and
Gross or Earthy parts.
[19] Paracelsus de Mineral. tract. 1. pag. m. 243
But though (_Pyrophilus_) I have observ'd a Red and Green to be produc'd,
the former, by Acid Salts, the later by Salts not Acid, in the express
Juices of so many differing Vegetable Substances, that the Observation, if
persued, may prove (as I said) of good Use: yet to show you how much e'vn
these Effects depend upon the particular Texture of Bodies, I must subjoyn
some cases wherein I (who am somewhat backwards to admit Observations for
Universal) had the Curiosity to discover, that the Experiments would not
Uniformly succeed, and of these Exceptions, the chief that I now remember,
are reducible to the following three.
_EXPERIMENT XXVI._
And, (first) I thought fit to try the Operation of Acid Salts upon
Vegetable Substances, that are already and by their own Nature Red. And
accordingly I made Trial upon Syrrup of Clove-july-flowers, the clear
express'd Juice of the succulent Berries of _Spina Cervina_, or Buckthorn
(which I had long kept by me for the sake of its deep Colour) upon Red
Roses, Infusion of Brazil, and divers other Vegetable Substances, on some
of which crush'd (as is often mention'd) upon White Paper, (which is also
to be understood in most of these Experiments, if no Circumstance of them
argue otherwise) Spirit of Salt either made no considerable Change, or
alter'd the Colour but from a Darker to a Lighter Red.


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