Though a ſingle grain of copper diſſolved in upwards of twenty gallons of clear water may be detected by a viſible blue tinge appearing on the addition of a few drops of volatile alcali, yet this is by no means the caſe in turbid high-coloured liquors, … Hence the neceſſity of diluting ſuch liquors in varying the experiments. In no inſtance did the blue tinge appear with the alcalis, even after the wine was diluted, and yet its abſence does not prove the liquor to be abſolutely free from an impregnation of copper.