Page:The New International Encyclopædia 1st ed. v. 20.djvu/263

* VOLTAIC CELL. 215 VOLTAIRE. ZnF pn I --:zl^= I ^^■^ Dil-^ there is no further heat of dilution, this electro- motive force is the residual obtained from the Gibbs-Helmholtz equation, or T X ciE/dT. It ia proportional to the absolute temperature of the cell. Fig. 16 represents a Zn-ZnSO, concentration cell. Th(' direction of the electromotive force within the cell is shown by the long arrow in the solutions. The sliort arrows sliow the direc- tion of the thermo-electro- motive forces at the two electrodes. This thermo-elec- tromotive force increases in value with an increase in the concentration of the elec- trolyte, and the relation be- tween the two is a perfectly definite one. Hence the ori- gin of the electromotive force in a (concen- tration cell may be regarded as theniial en- tirely and equal to the dilTercnee of the two thermo-electromotive forces on the two sides of the cell. There is also probably a small electro- motive force at the contact of the two solutions. Such a cell converts the heat of its surroundings into the energy of a current, but it does not con- tradict the second law of thermodynamics, be- cause the process involved does not constitute a cycle of operations. Such a system as this can- not by repeated cooling convert into work the heat of neighboring bodies, because the concen- trations are equalized by the flow of current, and then there is no further electromotive force. On the Nernst theory the fornuila for the elec- tromotive force of a concentration cell becomes Fig. 16. CONCENTRA- TION CELL. E — 0.0002 ■ T log - ■2i' n u--v In this formula i expresses the degree of disso- ciation of the dissolved salt, « and v are the migration velocities of the positive and negative ions respectively, and c, and c, are the two con- centrations. Nernst has applied his theory to a concentra- tion cell consisting of silver electrodes in solu- tions of silver nitrate, the concentrations being as 1 to 10. The measured electromotive force was 0.055 volt at 18° C, and the calculated value, 0.0574. The two are in very satisfactoiy agi-ee- ment. Similar concentration cells may be made by employing a single solution and amalgams in contact with it, the two amalgams containing the metal ion in different degrees of concentra- tion. For example, zinc-mercury amalgams in contact with a solution of ziue sulphate give an electromotive force from the concentrated to the dilute amalgam through the cell. When a current flows the zinc goes into solution from the more concentr.ated amalgam, and zinc ions are set free at the surface of the weaker amal- gam. In this case the larger thermo-electromo- tive force is at the junction of the less concen- trated amalgam and the solution : and more heat is absorbed at the cathode than is generated at the anode. As in the other case, therefore, this cell converts heat into electric energy. Bibliography. Carliart, Primary Ratteries (Boston, 1891); Benjamin, The Voltaic Cell (New York. 1893) : Lehfeldt, Pliijsical Chem- istry (Loudon, 1899) ; Walker, Introduction to Physical Chemistry (ib., 1899) ; Cooper, Pri- mary liaiterivs (ib., 1901); Arrhenius, Electro- chemistry (ib., 1902) ; Jaeger, Die Normal- elemente (Halle, 1902) ; Nernst, Theoretische Chemic (Stuttgart, 1900). VOLTAIRE, v61't.^r'. The assumed name of Jean Fi{an(,ois JIarie Arouet (109-1-1778). A French philosopher and a versatile author, born in Paris in February, 1C94. He belonged to a good middle-class family, his father being first a notary and afterwards a treasurer at- tached to one of the high courts of tlie king- dom. Jean Francois was educated first at the Coll&ge Louis le Grand, then by the Jesuits, of whom he was soon one of the most brilliant scholars. His education was di- rected partly by his father, partly by a worldly ecclesiastic, the Abbfi de Chateauneuf, who intro- duced him to the most brilliant society of the last years of Louis XIV. Ilis school days were followed by a few years of rather dissipated life, which ended when he was taken to The Hague as secretary by tine French Ambassador to Holland, the Marquis de Chateauneuf, a kinsman of the Abbe. Having fallen into a dangerous love intrigue with a young huly of a refugee Huguenot family, Olympe Uuno3-er, he was sent back to Paris, and his father determined to shij) him off to the colonies, but relented on the j'oung man's promise to reform and to study jjrocedure in an attorney's ollice. In the freer life of the Regency, he soon became known as one of the most bril- liant and most .sarcastic wits of the period. His light and caustic repartees more than once brought him into trouble. He had twice to leave Paris by order of the Kegent, and finally, on ac- count of something he had written, and of other things wrongly ascribed to him, he was im- prisoned in the Bastille, where he remained eleven months (1717-18). His release was soon fol- lowed by the performance at the Theatre Frangais of his first tragedy, (Edipe, based on the CEdipus Tyrunnus oi Sophocles. The play was received with great applause, and the author was at once hailed as the legitimate heir of the great masters of French tragedy. About this time Arouet as- sumed the name of Voltaire, the origin of which has never been satisfactorily explained. The production of (Edipe (1718) may be con- sidered the beginning of his extraordinary lit- erary career. For a long time he was considered mainly a dramatic poet; yet even then he had conceived the idea of an epic poem devoted to the glory of Henry IV., and intended as a eulogy of the principle of religious toleration, and he hivd planned a great historical work relating the events of the reign of Louis XIV. From 1719 to 1726 he was occupied mainly with the produc- tion of plays, none of which repeated the success of his (Edipe, and with the composition of his epic poem, which, under the strict laws then governing the printing of literary works, he was unable to publish. This poem, known first as the Poeme de la Lieiue, was printed in Geneva (1723) and issued secretly, but met with considerable suc- cess. In his first philosophical poem, Le pour et le contre. both his anti-(ihristian views and his deistie philosophy found clear and eloquent ex- pression. This period of Voltaire's life is also marked by the beginning of his enmity toward a man who was then considered the greatest lyric