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

EXPERIMENT XLVII.

AS for the Adventitious Colours produc'd by the Union of Metals with their Sol∣vents; Gold gives Aqua Regis it's Yellow Colour, but Mercury gives no considerable Co∣lour to Aqua Fortis, except a Greenness or Blew∣ness at the first, which presently disappears. Tin corroded by Aqua Fortis, subsided in the form of curdl'd Milk or Eggs. Lead dissolv'd in Spirit of Vinegar, affords a clear Solution; and if the Menstruum be drawn off, appears White. Iron dissolv'd by Oyl of Vitriol diluted with Water, yields a Green Vitriolum Martis; but gives a Saffron Colour to Aqua Fortis, or a yellowish Red. Common Silver, such as is coin'd, gives a Copper Tincture to Aqua fortis; but such as is refin'd perfectly, gives a blewish Green to Aqua fortis, and Spirit of Vinegar; and being sublim'd with Sal Armoniac, it affords a blewish Sublimate: And indeed Copper dis∣solv'd in several Menstruums will yield a great Variety of Greenish Blew or blewish Green Co∣lours. But with Spirit of Sugar and Turpen∣tine it affords a Blew Tincture with a mixture of Green. And to shew that the Adventitious Colour may result from the Copper it self as well as the Salts which Corrode it, I moistned

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Dantzick Vitriol with Spittle, and then rubbing it upon a Knife, it gave it a redish Colour like that of Copper. Saccharum Saturni with Spirit of Turpentine will yield a red Balsam; and that Stone which Helmont calls Paracelsus his Ludus, in a proper Menstruum affords sometimes a yellowish and sometimes a red Solution.

And before I leave this Experiment I shall add that if Quicksilver be precipitated out of Aqua fortis with Spirit of Sea-salt, or Sea-salt dis∣solv'd in Water, it will subside in the form of a white Powder; but if it be precipitated with an Alkaly it yields a yellow tawny Powder; but if the Menstruum be drawn off without pre∣cipitating it, the remaining substance, will vary it's Colour, as it is expos'd to different degrees of Heat; so that once I observ'd the white Calx, to remain partly in the bottom of the Vial, of a deep Yellow, and in some part Red, the remaining Part being elevated in the form of a reddish and ash-colour'd Sublimate. And Vermilion, is only a Sublimate of Mercury and Brimstone.