Theſe, of all my Experiments on Copper, are what have afforded me the greateſt Satiſfaction in the Subject of the preſent Enquiry; as they ſhew, that Nature is ſo far from being tied to one ſingle Menſtruum for producing the Sapphirine Colour from Copper, that inſtead of the Colours of the blue Gems being owing only to the Effects of a ſingle, ſcarce, indeed uncertain Menſtruum on that Metal, we find they are producible from the Action of others, and thoſe the moſt common, moſt abundant, and indeed, univerſal Menſtruums of the foſſile World. We need be no longer at a Loſs to find where Nature could meet with a ſufficient Quantity of a proper Menſtruum to extract from Copper the Colour neceſſary for the various blue Gems, when we ſee, that the univerſal native foſſile Acid, whether in Form of Vitriol, Sulphur, or Alum, and unqueſtionably not leſs when alone; and even the nitrous, under proper Limitations, are able abundantly to produce it.
Of the vegetable Acids, diſtilled Vinegar, Lemon-juice, and Spirit of Verdigreaſe, all give green Solutions of Copper; but with this Difference, that the firſt gives ſome faint Bluiſhneſs with the Green; the ſecond is a pale whitiſh 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 ſeparable from Solutions with them,
