The Boy's Playbook of Science / Including the Various Manipulations and Arrangements of Chemical and Philosophical Apparatus Required for the Successful Performance of Scientific Experiments in Illustration of the Elementary Branches of Chemistry and Natural Philosophy

by John Henry Pepper

Fourteenth Experiment.

The safest and surest mode of making a gilding solution is to dissolve some cyanide of potassium in water in a gallipot, and having placed a porous vessel therein containing the same solution, put a plate of copper into the porous cell, and some thin foil of pure gold into the gallipot; connect the gold with the anode of a single cell of Daniell, and the copper in the porous cell with the cathode, and in a few hours sufficient gold will be dissolved for the purpose of gilding.

It is usually recommended to warm the gilding solution till it reaches a temperature of about 150° Fahr., and a very moderate battery power is employed in Electro Gilding. Indeed the same arrangement, shown in the Eleventh Experiment, (Fig. 189.) [Page 202], will also answer for the gilding solution. After being gilt, the articles may be rubbed with a little tripoli, or burnished (with taste) by the handle of a key.

Fifteenth Experiment.

Passing on to the more brilliant results obtainable from a powerful voltaic battery (of at least thirty pairs of Grove), the beautiful incandescence of platinum wire may first be noticed. If a wire of this metal is stretched between the brass standards of two ring stands, the length must be proportioned to the power of the battery; the adjustment can be made very conveniently by twisting the platinum wire on one ring stand, and then leaving the other end loose, the second ring stand may be brought nearer and nearer to the first, until the desired intensity of light from the incandescent wire is obtained. (Fig. 190.) If the wire is contained in a glass tube the cooling effect of currents of air is prevented, and a much greater length of wire can be made hot.

Fig. 190.

a a. Two ring stands with the battery wires b b (which should be a convenient length) attached. c. Platinum wire, fixed end. d. The other end held in one hand and shortened as the stand is moved by the other hand.

Sixteenth Experiment.

With the same arrangement, a chain composed of alternate links of silver and platinum wire presents a very pretty effect, every alternate link of platinum being incandescent, whilst the silver, from its excellent conducting power, remains comparatively cool.