Melt a small quantity of the sulphate of potash and copper in a spoon over a spirit lamp. It will be fused at a heat just below redness, and produce a liquid of a dark-green color. Remove the spoon from the flame, when the liquid will become a solid of a brilliant emerald green color, and so remain until its heat sinks nearly to that of boiling water, when suddenly a commotion will take place throughout the mass, beginning from the surface, and each atom, as if animated, will start up and separate itself from the rest, till in a few moments the whole will become a heap of powder.