Take a piece of packthread, or cotton thread, boil it in clean water to
free it from saline particles, and dry it; wet one end, and take upon
it a little of either of the salts hereafter named, in fine powder, or
strong solution. Then dip the wetted end of the thread into the cup of
a burning wax candle, and apply it to the exterior of the flame, not
quite touching the luminous part, but so as to be immersed in the cone
of invisible but intensely heated air which envelopes it. Immediately,
an irregular sputtering combustion of the wax on the thread will take
place, and the invisible cone of heat will be rendered luminous, with a
peculiarly coloured light, according to the salt employed.
Thus, common salt will give a bright yellow; muriate of potass will
give a beautiful pale violet; muriate of lime will give a brick red;
muriate of strontia will give a magnificent crimson; muriate of lithia
will give a red; muriate of baryta will give a fine pale apple green;
muriate of copper will give a beautiful bluish green; and green
copperas will give a white light.