The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

EXPERIMENT XXXVI.

ONE thing to be observ'd in the Experi∣ments above recited is, that tho' the Co∣lours mention'd, are easily produc'd; yet some of them presently fade, by the Influence of the Air, or the Intestine Motion of their own Parts. And Parkison tells us, that Berries of that Plant, which bears Turnsol, a Pigment well known in Painters Shops, when they are at their full Maturity, yield a Juice, which being rubb'd upon Paper appears green, but pre∣sently degenerates into a blewish Purple, upon the Cloth or Paper; and these being wet in Wa∣ter, and wrung forth, will give it a Claret Colour. And I have observ'd the Red Colour of Buckthorn Berries degenerate into a dirty Grey Colour; yet by the Mixture of an Alkaly or an Acid it would put on a green or red Colour; and the same Success we had when we dropp'd the same Li∣quor upon a Piece of glaz'd Tile. And I have observ'd, that Silver precipitated in Aq. Fortis, tho' at the first it is white, yet when upon a

Decantation of the Liquor, the Superficies be∣comes expos'd to the Air, it presently turns blackish. And I have seen a sort of Pears, which would give a red Tincture to Wine. And it is observ'd, that Spirit of Wine being kept upon white Salt of Tartar, acquires a red Tincture. But as for the reasons of these things, and also why all Bodies burnt in the open Air almost, are black, I shall leave to Pyrophilus to en∣quire.