Fig. 182.
a a. Amalgamated zinc plate in flat earthenware trough. Attached to a binding screw is the platinum plate in porous cell, c c. d. A series of single cells forming a Grove's battery.
A continuous arch of flame was produced between two charcoal points, when distant from each other three quarters of an inch, and the light and heat were so intense that the professor's face became scorched and inflamed, as if it had been exposed to a summer heat. The rays collected by a lens quickly fired paper held in the focus.[C]
[C] By the light from the same battery photogenic drawings were taken, and the heating power was so great as to fuse with the utmost readiness a bar of platinum one-eighth of an inch square; and all the more infusible metals, such as rhodium, iridium, titanium, &c., were melted like wax when placed in small cavities in hard graphite and exposed to the current of electricity.
Fourth Experiment.
It is by "chemical action" the electricity is produced, and as action and reaction are always equal, but contrary, we are not surprised to find that the electricity from the voltaic battery will in its turn decompose chemically many compound bodies, of which water is one of the most interesting examples. It was in the year 1800, and immediately after Volta's announcement to Sir Joseph Banks of his discovery of the pile, that Messrs. Nicholson and Carlisle constructed the first pile in England, consisting of thirty-six half-crowns, with as many discs of zinc and pasteboard soaked in salt water. These gentlemen, whilst experimenting with the pile, observed that bubbles of gas escaped from the platinum wires immersed in water and connected with the extremities of the Volta's pile, and covering the wires with a glass tube full of water, on the 2nd of May, 1800, they completed the splendid discovery of the fact that the Volta's current had the power to decompose water and other chemical compounds.
In 1801, Davy had succeeded to a vacant post in the Royal Institution, and on Oct. 6th, 1807, made his transcendent discovery of potassium with the aid of the voltaic battery, and from that and other experiments inferred that the whole crust of the globe was composed of the oxides of metals. To exhibit the decomposition of water, two platinum plates with proper connecting wires, passing to small metallic cups full of mercury, are cemented inside a glass vessel, which is then filled with dilute sulphuric acid. Just above the platinum plates and over them, stand two glass tubes also containing the same fluid in contact with the battery. Two measures of hydrogen are found in one tube, and one of oxygen in the other. (Fig. 183.)
Fig. 183.