First Experiment.
Box and various woods, dried bones, and different organic matters, placed in a nearly close iron or other vessel, and heated red hot, so that all volatile matter may escape, leave behind a solid black substance called charcoal. If that kind obtained from bones, and termed bone black or ivory black, is roughly powdered, and placed in a flask with some solution of indigo or some vinegar, or syrup obtained by dissolving common moist sugar in water, and boiled for a short period, the colour is removed, and on filtering the liquid it is found to be as clear and colourless as water, provided sufficient ivory black has been employed.
Second Experiment.
Charcoal is a disinfectant, and is used for respirators; it has even been recommended medically, and charcoal lozenges can be bought at various chemists' shops. If a few drops of a strong solution of hydrosulphuret of ammonia (which has the agreeable odour belonging to putrid eggs) is mixed with half a pint of water, it will of course smell strongly, and likewise precipitate Goulard water, or a solution of acetate of lead black; but on shaking the water with a few ounces of charcoal, it no longer smells of sulphuretted hydrogen, and if filtered and poured into a solution of lead does not turn it black. This chemical action of charcoal, independent of its seeming mechanical attraction for colouring matter, would appear to show that the pores of charcoal contain oxygen, which in that peculiar condensed state destroys colouring matter, and oxidizes other bodies.
Third Experiment.
A very satisfactory experiment, proving that the diamond and plumbago or black lead are identical with charcoal, although differing in outward form and purity, can be made at a little cost, by purchasing a fragment of refuse diamond, called "boart," of Mr. Tennant of the Strand. A small piece costs about five shillings. The fragment should be carefully supported by winding some thin platinum wire round it, as, if the wire is too thick, it cools down the heat of the bit of diamond and prevents it kindling in the oxygen gas. A difficulty may arise in preparing the fragment, in consequence of the wire continually slipping off. The "boart" should therefore be grasped by the thumb and first finger, and the wire wound round; then it must be carefully turned and again wound across with the platinum wire, as in the sketch below. (Fig. 145.)
Fig. 145.
a. The platinum wire. b. The fragment of "boart" or refuse diamond.