Pliny deſcribes by, Quorum extremus igniculus in flavedinem exeat. The Solution in Spirit of Nitre is of the true Emerald Colour, and extremely bright and vivid; and each of the others reſembles very exactly the Colour of a particular Gem of the ſame Claſs; the firſt of them being perfectly of the Colour of the yellowiſh green Praſius, and the third of the Smaragdo-praſius.
Theſe Colours are each of them very beautiful; and that of the Solution in Agua regia is no other than what muſt be expected, when we know the Colours of the other two, the Spirits of Salt and Nitre being ſimple Menſtruums, and affording a green, and a yellowiſh green Solution; and the Agua regia, a compound Menſtruum, partaking of the Nature of both the others, it muſt naturally give a Solution of a Colour between both, that is a Green with leſs Yellow than that of the Spirit of Salt.
But though theſe three acid Menſtruums afford green Solutions of this Metal, it is too haſty a Concluſion to infer from thence, that all the Acid Menſtruums will therefore do the ſame; for Solutions of Copper in Oil of Vitriol, Oil of Sulphur, and Agua fortis, are all blue. They are in different Degrees, tho' all nearly approaching to each other, and the deepeſt of them not darker than that of the common Turquoiſes. Theſe Solutions have alſo this peculiar Property, that they immediately precipitate their Copper on Iron, if immerſed in
them;
