Page:Theophrastus - History of Stones - Hill (1774).djvu/352

 Thing; the ame univeral mineral Acid, exeitent every where in the Earth, and ometimes perceivable by the Senes, in the uffocating Damps of Mines, being the certain Bais of both; as alo of a third, that of Alum: And though the different Matter it meets with in Alum, Vitriol, and Sulphur, gives it a different Appearance in the Concrete, yet when freed from that Matter by Chemitry, and rendered as pure as that Art will make it, it appears the ame Thing, whether drawn from one or the other of thee Subtances.

That Oil of Vitriol, therefore, and Oil of Sulphur, hould produce a Solution of Copper of the ame Colour, is no other than what mut naturally be expected: But that Agua fortis, which is a compound Mentruum, and made, though partly from Vitriol, which affords a blue Solution, yet partly alo from Nitre, which we have een before affords a fine green one, hould give a imply blue Solution, as it evidently does, without the leat Admixture of Green, may eem, at firt View, omething trange. But here I mut oberve, that Spirit of Nitre is the Mentruum I hinted at in the Beginning of this Letter, as capable of affording different Colours, from different Quantities of the Metal diolved in it. And nothing, indeed, is more certain, than that the greenet Solution of Copper in Spirit of Nitre, may be turned into a pale Blue, only by adding more and more Filings of the ame Metal, up to the proper Quantity for the Change. Thee,