of the adventitious Colours of Mineral Bodies; which brings into my mind, that, ev'n Vegetable Liquors, whether by degeneration, or by altering the Texture of the Body that imbibes them, may ſtain other Bodies with Colours differing enough, from their own, of which very good Herbariſts have afforded us a notable Example, by affirming that the Juice of Alcanna being green (in which ſtate I could never here procure it) do's yet Dye the Skin and Nails of a Laſting Red. But I ſee this Treatiſe is like to prove too bulky without the addition of further Inſtances of this Nature.
EXPERIMENT XLIX.
Meeting the other day, Pyrophilus, in an Italian book, that treats of other matters, with a way of preparing what the Author calls a Lacca of Vegetables, by which the Italians mean a kind of Extract fit for Painting, like that rich Lacca in Engliſh commonly call'd Lake, which is imploy'd by Painters as a glorious Red. And finding the Experiment not to be inconſiderable, and very defectively ſet down, it will not be amiſs to acquaint you with what ſome Tryals have inform'd us, in reference to this
Experiment, which both by our Italian Author, and by divers of his Countrymen, is look'd upon as no trifling Secret.
Take then the root call'd in Latin Curcuma, and in Engliſh Turmerick, (which I made uſe of, becauſe it was then at hand, and is among Vegetables fit for that purpoſe one of the moſt eaſieſt to be had) and when it is beaten, put what Quantity of it you pleaſe into fair Water, adding to every pound of Water about a ſpoonfull or better of as ſtrong a Lixivium or Solution of Potaſhes as you can well make, clarifying it by Filtration before you put it to the Decocting water. Let theſe things boyl, or rather ſimper over a ſoft Fire in a clean glaz'd Earthen Veſſel, till you find by the Immerſion of a ſheet of White Paper (or by ſome other way of Tryal) that the Liquor is ſufficiently impregnated with the Golden Tincture of the Turmerick, then take the Decoction off the Fire, and Filter or Strain it that it may be clean, and leiſurely dropping into it a ſtrong Solution of Roch Allum, you ſhall find the Decoction as it were curdl'd, and the tincted part of it either to emerge, to ſubſide, or to ſwim up and down, like little Yellow flakes; and if you pour this mixture into a Tunnel lin'd with Cap Paper, the Liquor that Filtred formerly
ſo Yellow, will now paſs clean thorow the Filtre, leaving its tincted, and as it were curdled parts in the Filtre, upon which fair Water muſt be ſo often pour'd, till you have Dulcifi'd the matter therein contain'd, the ſign of which Dulcification is (you know) when the Water that has paſs'd through it, comes from it as taſteleſs as it was pour'd on it. And if without Filtration you would gather together the flakes of this Vegetable Lake, you muſt pour a great Quantity of fair Water upon the Decoction after the affuſion of the Alluminous Solution, and you ſhall find the Liquor to grow clearer, and the Lake to ſettle together at the bottom, or emerge to the top of the Water, though ſometimes having not pour'd out a ſufficient Quantity of fair Water, we have obſerv'd the Lake partly to ſubſide, and partly to emerge, leaving all the middle of the Liquor clear. But to make this Lake fit for uſe, it muſt by repeated affuſions of freſh Water, be Dulcifi'd from the adhering Salts, as well as that ſeparated by Filtration, and be ſpread and ſuffer'd to dry leiſurely upon pieces of Cloth, with Brown Paper, or Chalk, or Bricks under
them to imbibe the Moiſture[a]25].
Annotation I.
Whereas it is preſum'd that the Magiſtery of Vegetables obtain'd this way conſiſts but of the more Soluble and Coloured parts of the Plants that afford it, I muſt take the liberty to Queſtion the ſuppoſition. And for my ſo doing, I ſhall give you this account.
According to the Notions (ſuch as they were) that I had concerning Salts; Allom, though to ſenſe a Homogeneous Body, ought not to be reckon'd among true Salts, but to be it ſelf look'd upon as a kind of Magiſtery, in regard that as Native Vitriol (for ſuch I have had) contains both a Saline ſubſtance and a Metall, whether Copper, or Iron, corroded by it, and aſſociated with it; ſo Allom which may be of ſo near a kin to Vitriol, that in ſome places of England (as we are aſſur'd by good Authority the ſame ſtone will