ELECTROCHEMISTRY. That branch of chemistry which treats of the utilization of elec trical energy to facilitate or carry on a chemical reaction is known as electrochemistry. This end may be accomplished in one of three ways: by electrolysis, by electrothermal action, or by the discharge of electricity through gases. Con versely, electrochemistry also includes those re actions by which electricity is generated by means of chemical action. It was the Italian physicist Alessandro Volta (q.v.), a professor in the University of Pavia, who first discovered that when two metals and a liquid are combined in a circuit an electric current is prOduced. It was also Volta, who, for the first time, distin guished between the two classes of electrical conductors, recognizing the difference between metallic conductors and electrolytic conductors, which is the foundation of all electrolytic work. Soon after this he established what has been called the contact electromotive series, which is a table of metallic conductors arranged in such order that if any two of them be connected with each other and also with an electrolytic conductor, an electric current will flow through the liquid from the metal higher in the series to the one lower in the series, and the current increases in magnitude the farther apart the two metals are in the series. Following this, it was discovered by Ritter, that the order of the metals in this series was the same as the previ ously known order in which metals replaced each other in solutions of their salts. This dis covery was the first bond of linkage between the newer science of electricity and the older one of chemistry, and marks the birth of our modern electrochemistry. Volta's contact elec tromotive series soon led to the development of the voltaic pile (q.v.), the first device for the generation of electric current, and one depend ent entirely on electrochemical principles. In his work on the pile, Volta could hardly have failed to notice the formation of gas bubbles on the metals immersed in his solutions, and the fact that he makes no mention of these phenomena indicates that he did not appreciate the significance of the reactions that were tak ing place. It remained for Nicholson and Carlisle in 1800 to record the formation of hydrogen and oxygen on passing the electric current through water. In the study of the
various decompositions it was soon noted that there was a formation of alkali at the negative pole in the electrolysis and of acid at the posi tive pole. Following up these observations led to the discovery by Davy in 1807 of the alkali metals, sodium and potassium, which he separated by electrolysis of the fused hydrates, thus laying the foundation for the development 100 years later of the Castner process of manu facture of metallic sodium on a commercial scale. (See ELECTROCHEMICAL I NDUSTRIES ) It was Berzelius, the great Swedish chemist, who devised the first theory for the explanation of the nature of chemical compounds, based upon elec trochemical observations. The Beraelius theory dominated this new science and the parent science of chemistry as well for many decades, but in turn was supplanted by other theories. During its lifetime, however, it served as the basis for an enormous amount of valuable dis cussion and research. According to the Berze lius theory, chemical atoms behave similarly to a magnet, having a positive and negative pole, but in the case of some elements the positive pole is much the stronger of the two and in others the negative pole is the stronger. Con sequently the atom behaves in accordance with the character of the predominating pole, and the positive or negative character of the pre dominating pole of the atoms, and its relative strength, determine the chemical character of the element. Atoms of an electropositive char acter can then combine with those of electro negative character, in proportions determined by their relative strength, thus neutralizing each other more or less, but not necessarily completely. If complete neutralization does not result from the first combination the result is a compound which is more or less electro positive or electronegative, depending on which charge predominates, and compounds of this kind of opposite polarity can still further com bine for more complete neutralization. Com binations of certain elements thus gave com pounds of an acid character while others gave compounds of a basic character, and these com bine to form salts, which, if not completely neutralized, can still further combine to form double salts.