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

EXPERIMENT XV.

IT is Taught by the Chymists, that Black∣ness depends on Sulphur adust. But besides what hath been already offer'd as the cause of Blackness, I shall add, in reference to the Opi∣nion here propos'd, that common Sulphur sub∣lim'd, is far from black, but it is in a great measure yellow, and rather more than less white than before; and when set on fire to make O∣leum Sulph. per campanam, it yields very little Soot; and the Flame yields so little, that it will scarce black a white Sheet of Paper; and it is observ'd rather to whiten than to black Linnen, and makes red Rose Leaves grow pale and not black. And I have seen a Piece of fix'd Sulphur, which was kept several Weeks in a violent Heat, yet it had no other Colour when cool, but a pure red. And not only Sulphur, but that sulphureous Body Camphire may be kept in a violent Heat without acquiring any thing of Blackness: Nor will inflammable Spi∣rit of Wine, discolour a piece of Paper held o∣ver it whilst it consumes. And Tin calein'd, yields not a black, but a white Calx; and not only the Charcoal made of Oxy-Cedar is white, but the Smoak of Tinby Coals is observ'd rather to blanch Linnen than black it: To what hath been said we may add, that the Ingredients of our Ink were not hot but cold; and Juice of Li∣mons will blacken the Blade of Knife, except it be quickly wiped off, tho' no actual Heat in∣tervenes to adust the Sulphur. And if the Black∣ness

of the Ink depended on adust Sulphur, it might be demanded, what became of those a∣dust Particles, when the Liquor, by a few drops of Oyl of Vitriol, lost that Colour. Besides, Soot it self may have it's Texture so far alter'd, as to yield a Crystalline Salt and a transparent Colour.

But were it allow'd, since Adustion renders some Bodies black, that that Colour depended on a trorrify'd Sulphur, it might be further demanded, what gives torrify'd Sulphur that Colour; and it might be question'd, what makes a Window half shut, at a distance to appear black, since it hath no Access of torrify'd Sulphur upon that Posture, but only the Rays of Light are not so plentiflly reflected by it, as is requisite to affect the Senso∣ry with a more lively Colour; But to conclude. What the Chymists teach of Blackness, to me seems to come to no more, than if in answer to an Enquiry after the Cause of Salivation, they should tell us, that the several kinds of Precipi∣tates of Gold and Mercury, and likewise of Quicksilver and Silver salivate upon Account of the Mercury that abounds in them, where we are still at a loss to know why Mercury should have that Effect.