in the discovery and research of electric arc effects. Humphry Davy and Andrew Crosse were among the first to develop large voltaic piles. Davy used a 2000-pair pile made for the Royal Institution in 1808 to demonstrate carbon arc discharge and isolate five new elements: barium, calcium, boron, strontium and magnesium. Electrochemistry Because Volta believed that the electromotive force occurred at the contact between the two metals, Volta's piles had a different design than the modern design illustrated on this page. His piles had one extra disc of copper at the top, in contact with the zinc, and one extra disc of zinc at the bottom, in contact with the copper. Expanding on Volta's work and the electro-magnetism work of his mentor Humphry Davy, Michael Faraday utilized both magnets and the voltaic pile in his experiments with electricity. Faraday believed that all "electricities" being studied at the time (voltaic, magnetic, thermal, and animal) were one and the same. His work to prove this theory led him to propose two laws of electrochemistry which stood in direct conflict with the current scientific beliefs of the day as laid down by Volta thirty years earlier. Because of their contributions to the understanding of this field of study, Faraday and Volta are both considered to be among the fathers of electrochemistry. The words "electrode" and "electrolyte", used above to describe Volta's work, are due to Faraday. Electromotive force The strength of the pile is expressed in terms of its electromotive force, or emf, given in volts. Alessandro Volta's theory of contact tension considered that the emf, which drives the electric current through a circuit containing a voltaic cell, occurs at the contact between the two metals. Volta did not consider the electrolyte, which was typically brine in his experiments, to be significant. However, chemists soon realized that water in the electrolyte was involved in the pile's chemical reactions, and led to the evolution of hydrogen gas from the copper or silver electrode. The modern, atomistic understanding of a cell with zinc and copper electrodes separated by an electrolyte is the following. When the cell is providing an electrical current through an external circuit, the metallic zinc at the surface of the zinc anode is oxidized and dissolves into the electrolyte as electrically charged ions (Zn2+), leaving 2 negatively charged electrons () behind in the metal: anode (oxidation): Zn → Zn2+ + 2 This