Page:Theophrastus - History of Stones - Hill (1774).djvu/353

 Thee, of all my Experiments on Copper, are what have afforded me the greatet Satifaction in the Subject of the preent Enquiry; as they hew, that Nature is o far from being tied to one ingle Mentruum for producing the Sapphirine Colour from Copper, that intead of the Colours of the blue Gems being owing only to the Effects of a ingle, carce, indeed uncertain Mentruum on that Metal, we find they are producible from the Action of others, and thoe the mot common, mot abundant, and indeed, univeral Mentruums of the foile World. We need be no longer at a Los to find where Nature could meet with a ufficient Quantity of a proper Mentruum to extract from Copper the Colour neceary for the various blue Gems, when we ee, that the univeral native foile Acid, whether in Form of Vitriol, Sulphur, or Alum, and unquetionably not les when alone; and even the nitrous, under proper Limitations, are able abundantly to produce it.

Of the vegetable Acids, ditilled Vinegar, Lemon-juice, and Spirit of Verdigreae, all give green Solutions of Copper; but with this Difference, that the firt gives ome faint Bluihnes with the Green; the econd is a pale whitih Green; and the third, the true, pure, and unmixed Green of the Emerald.

The fermented vegetable Acids, therefore, have more Effect on this Metal than the native; this is evident from the deeper Colour, and from the much greater Quantity of the Metal eparable from Solutions with them, made