|Volta, Alessandro (1745-1827)|
| Italian physicist who invented
the first electric cell (the voltaic pile, 1800), the electrophorus (an
early electrostatic generator, 1775), and an electroscope.
In 1776 Volta discovered methane by examining marsh gas found in Lago Maggiore. He then made the first accurate estimate of the proportion of oxygen in the air by exploding air with hydrogen to remove the oxygen. In about 1795, Volta recognized that the vapour pressure of a liquid is independent of the pressure of the atmosphere and depends only on temperature.
Volta was born in Como; he became professor there 1775 and was professor at Pavia 1778-1819. The volt is named after him.
Volta's electrophorus consisted of a disc made of turpentine, resin, and wax, which was rubbed to give it a negative charge.
A plate covered in tin foil was lowered by an insulated handle on to the disc, which induced a positive charge on the lower side of the foil. The negative charge that was likewise induced on the upper surface was removed by touching it to ground the charge, leaving a positive charge on the foil. This process could then be repeated to build up a greater and greater charge. Volta went on to realize from his electrostatic experiments that the quantity of charge produced is proportional to the product of its tension and the capacity of the conductor.
Volta repeated and built on Italian physiologist Luigi Galvani's experiments with metals and the muscles of dead animals, and in 1792, Volta concluded that the source of the electricity was in the junction of two different metals and not, as Galvani thought, in the animals. Volta even succeeded in producing a list of metals in order of their electricity production based on the strength of the sensation they made on his tongue, thereby deriving the electromotive series.
In 1800 Volta described two arrangements of conductors that produced an electric current. One was a pile of silver and zinc discs separated by cardboard moistened with brine, and the other a series of glasses of salty or alkaline water in which bimetallic curved electrodes were dipped. Volta's electric cell was a sensation, for it enabled high electric currents to be produced for the first time.