Experiments and considerations touching colours first occasionally written, among some other essays to a friend, and now suffer'd to come abroad as the beginning of an experimental history of colours / by the Honourable Robert Boyle ...

EXPERIMENT XXVIII.

Another sort of Instances to show, how much changes of Colours effected by Salts, depend upon the particular Texture of the

Colour'd Bodies, has been afforded me by several Yellow Flowers, and other Vege∣tables, as Mary-gold Leaves, early Prim-roses, fresh Madder, &c. For being rubb'd upon White Paper, till they im∣bued it with their Colour, I found not, that by the addition of Alcalizate Liquors, nor yet by that of an Urinous Spirit, they would be turn'd either Green or Red: nor did so Acid a Spirit, as that of Salt, consi∣derably alter their Colour, save that it seem'd a little to Dilute it. Only in some early Prim-roses it destroy'd the greatest part of the Colour, and made the Paper almost White agen. And Madder also afforded some thing peculiar, and very differing from what we have newly men∣tion'd: For having gather'd some Roots of it, and, (whilst they were recent) ex∣press'd upon White Paper the Yellow Juice, an Alcalizate Solution drop'd upon it did not turn it either Green or White, but Red. And the bruis'd Madder it self being drench'd with the like Alcalizate Solution, exchang'd also its Yellowishness for a Redness.

An admonition touching the four preceding Experiments.

Having thus (Pyrophilus) given you divers Instances, to countenance the Gene∣ral observation deliver'd in the twenty fifth Experiment, and divers Exceptions where∣by it ought to be Limited; I must leave the further Inquiry into these Matters to your own Industry. For not remembring at present many of those other Trials, long since made to satisfie my self about Parti∣culars, and not having now the Oppor∣tunity to repeat them, I must content my Self to have given you the Hint, and the ways of prosecuting the search your Self; and only declare to you in general, that, As I have made many Trials, unmention'd in this Treatise, whose Events were agree∣able to those mention'd in the twenty fifth Experiment, so (to name now no other Instances) what I have try'd with Acid and Sulphureous Salts upon the Pulp of Juniper Berries, rubb'd upon White Pa∣per, inclines me to think, That among that vast Multitude, and strange Variety of Plants that adorn the face of the Earth, perhaps many other Vegetables may be found, on which such Menstruums may not

have such Operations, as upon the Juice of Violets, Pease-blossoms, &c. no nor upon any of those three other sorts of Vegeta∣bles, that I have taken notice of in the three fore-going Experiments. It sufficiently ap∣pearing ev'n by these, that the effects of a Salt upon the Juices of particular Vege∣tables do very much depend upon their particular Textures.