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

EXPERIMENT XLVI.

THe Adventitious Colours of Metals are either such as they acquire by the Action of the Fire upon them; or such as re∣sult from the Coalition of Metaline Particles with the Mestruum which dissolves them; or lastly when they are mix'd together by Fusi∣on.

And first Tin, by the Action of the Fire be∣ing calcin'd, affords a white Calx and Lead a Red one; and Copper calcin'd per se, yields a dark blackish Powder; and Iron by reverberated Flames may be turn'd into a Crocus, and Mer∣cury may be turn'd into a Red Powder. And,

Besides these more obvious Colours there are several intermediate ones, whilst by the Action of Fire, Metals are a Calcining. And not only the Calces, but the Glasses of Minerals vitrifi'd per se are of Colours different from the Metal; so that I have seen a Glass made of Silver, of a dark Colour.

And not only Metals, but Minerals may be brought to yeild Colours, by the Action of the Fire, different from their own, as Antimony

affords a whitish Gray Calx, and Flowers vari∣ously Colour'd; and the Calx by being flux'd will yield a Glass of a yellow or reddish Colour. And Vitriol Calcin'd passes through several Colours before it comes to be of a dark Pur∣ple.