Page:The New International Encyclopædia 1st ed. v. 20.djvu/256

* VOLSCI. 208 VOLTAIC CELL. territory was incorporated into Latiiim, and they themselves created Roman citizens. VOLSK, vol'y'sk. A town in the Goveru- ment of Saratov, Russia, situated on the right bank of the Volga, 91 miles northeast of Saratov (Map: Russia, G 4). It has extensive iron works, tanneries, etc. Population, in 1897, 27,039. VOLSXJNGASAGA, v6l'zung-a-za'ga. A thir- teenth century mythical history of the renovned old Germanic'fam'ily of the Volsungs, descendants of Odin. Sigurd or Siegfried, son of Sigmund, is the most noted hero of the race. VOLT ( from It. Tolta, name of the discoverer of the voltaic cell ). A unit of electric motive force, being 10' C. G. S. electromagnetic units. (See Electrical Units.) The electromotive force of two cells, the Clark and the Cadmium (or Weston), are known fairly accurately ; and so for practical purposes the electromotive force of a Clark or a Cadmium cell is used as the standard, and its value substituted in the result. Consult the paper by Gouy in the Reports of the Inter- national Congress of Physics (Paris, I90I). See olta:c Cell ob Batteky. VOL'TA. A river of Western Africa. It is formed in the northern part of the British Gold Coast Colony by the confluence of the Black and the White Volta", Hows southeastward, partly on the boundary of German Togoland, and empties into the Gulf of Guinea, 300 miles west of the mouths of the Xiger. Its total length, in- cluding the Black Volta,"is about 900 miles. The headstreanis rise in the savanna regions of French Sudan, but the main river flows within the forest belt. It is broken in several places by rapids, which, together with the bar at tlie mouth, are impassable at low water; but during the floods large vessels can ascend it about fifty miles, and smaller vessels 250 miles. VOLTA, vol'ta, Alessa:^dro, Count (1745- 1827). A celebrated Italian physicist, born at Como. While a youth he exhibited a considerable taste for letters, but as he grew older he devoted himself exclusively to science, especially to the study of electricity. In 1774 he was appointed professor of natural philosophy at the gymnasi- um of Coirm and in 1779 he became professor in the University of Pavia. At intervals be- tween 1777 and- I7S2 he visited Switzerland, Tuscany, Germany, Holland, France, and Eng- land, and is said to have introduced the culture of the potato into Lombardy. Napoleon, when First Consul, invited him to Paris to exhibit to the members of the Institute the 'pile' which he bad invented, and later created him Count and (Senator of the Kingdom of Italy. Volta proposed the theory, which was at vari- ance with the 'animal electricity' doctrine of Gal- vani, that the electric power resides in the metals and was due to their contact, although in turn lie fell into the error of supposing that the chemical action of the different kinds of metal on each other was only incidental. Volta is most famous as the inventor of the first electric battery. (See Voltaic Cell.) He also invented the electrophorus (q.v.), the condensing electro- scope, the electrometer, and also the hydrogen- lamp and the electrical pistol. Most of his im- portant discoveries were communicated by him directly to the Royal Society and were published in the Philosophical Transactions. A collection of Volta's works, in five volumes, was published in 1816 at Florence. VOLTAIC CELL or BATTERY. As early as 17(J0 Johann Sulzer announced to the Berlin Academy of Science the discovery that a peculiar bitter taste is perceived when two metals are placed on the tongue and touched at their edges. The significance of this observation was not ap- preciated till Volta had described his 'crown of cups' in 1800. The two metals, copper and zinc, for example, and the saline saliva compose, as is now known, a voltaic couple or cell. While pursuing his experiments to explain Galvani's discovery (see Galvanic Batteby), Volta, of the Universit.v of Pavia, was led to the invention of the voltaic pile, where two dis- similar plates, as zinc and copper, were placed the one on the other. Then followed a piece of cloth moistened with a weak solution of common salt. The cloth was surmounted by another pair of metal plates in the same order as the first, and so on, each pair being separated from ad- jacent ones by moist cloth, Volta's 'couronne de tasses,' or 'crown of cups,' was in principle essentially the same as a single couple of the pile. A series of cups contained brine or dilute acid; into the liquid dipped metallic strips, half zinc and half copper. The zinc end of a strip dipped into one cup. and the copper end into the next one. An electric current was taken from the terminal wires of the series. Such was the first voltaic cell on record. In the words of Sir Humphry Davy, "the voltaic battery was an alarm bell to experimenters in every part of Europe." On April 30, 1800, Nicholson and Carlisle discovered that water could be decom- posed by the electric current, and this important discovery was followed by Da-y's production of the electric arc light between two pencils of car- bon, the source of the current being a large vol- taic battery; and in 1807 he accomplished the electrol.vsis of the fixed alkalis, potash and soda, and discovered the corresponding metallic ele- ments, potassium and sodium. Volta's battery will be best understood by con- sidering a single sim])le cell. If a plate of zinc be placed in sulphuric acid, diluted with about twenty times its vol- ume of water, bubbles of hydrogen will at first collect on the zinc, but visible chem- ical action will soon cease. If now a plate of copper be iilaeed in the same solution no change will be ob- served so long as the two metals are kept out of contact ; but as soon as they are made to touch or are joined l)y wires (Fig. 1), vigorous chemical action sets in, the zinc wastes away, and hydrogen gas is freely lib- erated from the surface of the co])per plate instead of the zinc. This chemical action goes on only so long as the two plates are electrically connected. Such a combination of two con- ductors, immersed in a compound liquid, called an electrolyte, which is capable of reacting chem- Fk;. 1. .'tiMi'M-; voi,T,ic cEi.i..