Nature to the two former, made upon Syrrup of Violets, and Juice of
Blew-bottles. For as in them by the Affusion of Oyl of Tartar, a Blewish
Liquor is made Green, so in this, by the sole Mixture of the same Oyl, a
Greenish Liquor becomes Blew. The hint of this Experiment was given us by
the practice of some _Italian_ Painters, who being wont to Counterfeit
_Ultra-marine Azure_ (as they call it) by Grinding Verdigrease with
Sal-Armoniack, and some other Saline Ingredients, and letting them Rot (as
they imagine) for a good while together in a Dunghill, we suppos'd, that
the change of Colour wrought in the Verdigrease by this way of Preparation,
must proceed from the Action of certain Volatile and Alcalizate Salts,
abounding in some of the mingled Concretes, and brought to make a further
Dissolution of the Copper abounding in the Verdigrease, and therefore we
Conjectur'd, that if both the Verdigrease, and such Salts were dissolv'd in
fair Water, the small Parts of both being therein more subdivided, and set
at liberty, would have better access to each other, and thereby Incorporate
much the more suddenly; And accordingly we found, that if upon a strong
Solution of good French Verdigrease (for 'tis that we are wont to imploy,
as the best) you pour a just quantity of Oyl of Tartar, and shake them well
together, you shall immediately see a notable Change of Colour, and the
Mixture will grow thick, and not transparent, but if you stay a while, till
the Grosser part be Precipitated to, and setled in the Bottom, you may
obtain a clear Liquor of a very lovely Colour, and exceeding delightfull to
the Eye. But, you must have a care to drop in a competent Quantity of Oyl
of Tartar, for else the Colour will not be so Deep, and Rich; and if
instead of this Oyl you imploy a clear _Lixivium_ of Pot-ashes, you may
have an Azure somewhat Lighter or Paler than, and therefore differing from,
the former. And if instead of either of these Liquors, you make use of
Spirit of Urine, or of Harts-horn, you may according to the Quantity and
Quality of the Spirit you pour in, obtain some further Variety (though
scarce considerable) of Cæruleous Liquors. And yet lately by the help of