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Late Nineteenth Century Electrochemistry

In 1869 Zénobe Gramme devised his first clean direct-current dynamo (a generator using electromagnets) in which he drew upon the work of Pacinotti. His generator featured a ring armature wound with many individual coils of wire and on July 17, 1871 Gramme's invention was presented to the Académie des Sciences. To avoid eddy currents the core of his machine was built using iron wire insulated with bitumen. The most important part in this design, however, was the new type of commutator. In contrast to Pacinotti, who had not thoroughly grasped the essentials of commutation, Gramme almost completely solved the problem, which is widely considered as one of the most decisive technical inventions of the nineteenth century. In 1873 Gramme demonstrated that his direct-current dynamo can also work in reverse as a motor, allowing the commercial generation of electric power. The dynamos of Gramme were used in lighthouses, in electroplating, for manufactory's illumination and were driven by steam engines.

Friedrich Kohlrausch research in Germany was centered on determining how electricity was conducted in solutions. In his investigations to establish whether Ohm's law also applied to second class conductors, he was the first scientist to utilize alternating current. In this way, he prevented the deposition of decomposition products on the electrodes and obtained highly precise results in his measurements. He used a telephone to monitor the process. The result was that Ohm's law also found to apply to dissolved electrolytes. From 1875 to 1879, he examined numerous salt solutions, acids and solutions of other materials. His efforts resulted in the law of the independent migration of ions, that is, each type of migrating ion has a specific resistance no matter what its original molecular combination may have been, and therefore that a solution's electrical resistance was due only to the migrating ions of a given substances. Kohlrausch suggested that the more dilute a solution, the greater its conductivity.

Svante August Arrhenius published his thesis in 1884 on Recherches sur la conductibilité galvanique des électrolytes (Investigations on the galvanic conductivity of electrolytes). From his results the author concluded that electrolytes, when dissolved in water, become to varying degrees split or dissociated into electrically opposite positive and negative ions. The degree to which this dissociation occurred depended above all on the nature of the substance and its concentration in the solution, being more developed the greater the dilution. The ions were supposed to be the carriers of the electric current, e.g. in electrolysis, but also of the chemical activity. The relation between the actual number of ions and their number at great dilution (when all the molecules were dissociated) gave a quantity of special interest ("activity constant").

The race for a commercially viable route to aluminum was won in 1886 by two young men working independently, Paul Héroult in France and Charles M. Hall in the United States. The problem many researchers had with extracting aluminum was that electrolysis of an aluminum salt dissolved in water yields aluminum hydroxide. Both Hall and Héroult avoided this problem by dissolving aluminum oxide in a new solvent—fused cryolite, Na3AlF6. To scale up the process took Hall years of development and capital investment. In 1888 he joined with Alfred E. Hunt, an experienced metallurgist, to form the Pittsburgh Reduction Company.

After exhausting the initial investment, the fledgling company was buoyed by the resources of the Mellon banking interests. Almost immediately the price of aluminum dropped dramatically. Developments in the early 1880's had reduced the price of a pound of aluminum from twelve dollars to four dollars a pound. The Hall process reduced it to two dollars a pound, and shortly after the company's move to Niagara Falls, the first electrochemical company in that location, to seventy-five cents and then thirty cents. In 1907 the company was renamed the Aluminum Company of America, and in the 1990's this name was shortened to Alcoa.

Friedrich Ostwald , 1909 Nobel Laureate, started his experimental work in 1875, with an investigation on the law of mass action of water in relation to the problems of chemical affinity, with special emphasis on electrochemistry and chemical dynamics. In 1894 he gave the first modern definition of a catalyst and turned his attention to catalytic reactions. Ostwald is especially known for his contributions to the field of electrochemistry, including important studies of the electrical conductivity and electrolytic dissociation of organic acids. He developed a theory of solutions based on ionic dissociation and an analogy between gases and chemical solutions similar to Arrhenius's. He invented a viscometer that is still used for measuring the viscosity of solutions. Curiously enough, although he was one of the most eminent chemists of his time, he did not accept the development of atomic theory until 1906.

Edward Weston helped revolutionize the measurement of electricity. In 1886 he developed a practical precision, direct reading, portable instrument to accurately measure electrical current, a device which became the basis for the voltmeter, ammeter and watt meter. The Weston Standard Cell, developed in 1893, was recognized as an international standard and was used by the National Bureau of Standards for almost a century to calibrate other meters. It had the advantage of being less temperature sensitive than the previous standard, the Clark cell. It also had the advantage of producing a voltage very near to one volt: 1.0183 V.

In 1889, Ludwig Mond and his assistant Charles Langer described their experiments with a hydrogen-oxygen fuel cell that attained 6 amps per square foot (measuring the surface area of the electrode) at 0.73 volts. Mond and Langer's cell used electrodes of thin, perforated platinum. They noted difficulties in using liquid electrolytes, saying "we have only succeeded by using an electrolyte in a quasi-solid form, viz., soaked up by a porous non-conducting material, in a similar way as has been done in the so-called dry piles and batteries." An example given is an earthenware plate "impregnated by dilute sulfuric acid." The term "fuel cell" was coined (or at least popularized) in 1889 by Ludwig Mond and Charles Langer, when they attempted to use air and coal gas to generate electricity.

Carl Gassner produced the first "dry" cell in 1888 with zinc as the container for the other elements as well as for the negative electrode. The electrolyte was absorbed in a porous material and the cell was sealed across the top. This cell was easy to handle and portable. It became the prototype for the dry battery industry.

Hermann Nernst's developed the theory of the electromotive force of the voltaic cell in 1888. He developed methods for measuring dielectric constants and was the first to show that solvents of high dielectric constants promote the ionization of substances. Nernst proposed the theory of solubility product, generalized the distribution law, and offered a theory of heterogeneous reactions.

Nernst's early studies in electrochemistry were inspired by Arrhenius' dissociation theory which first recognized the importance of ions in solution. In 1889 he elucidated the theory of galvanic cells by assuming an "electrolytic pressure of dissolution" which forces ions from electrodes into solution and which was opposed to the osmotic pressure of the dissolved ions. In the same year he derived equations which defined the conditions by which solids precipitate from saturated solutions. Nernst applied the principles of thermodynamics to the chemical reactions proceeding in a battery. In 1889, he showed how the characteristics of the current produced could be used to calculate the free energy change in the chemical reaction producing the current. Nernst first explained the ionization of certain substances when dissolved in water. He constructed an equation, known as Nernst Equation, which related the voltage of a cell to its properties.

Nernst and his students in Berlin proceeded to make many important physico-chemical measurements, particularly determinations of specific heats of solids at very low temperatures and of vapor densities at high temperatures. All these were considered from the point of view of quantum theory. In 1914 Walther Hermann Nernst and Max Planck succeeded in bringing Albert Einstein to Berlin.

In 1898 Fritz Haber published his textbook on Electrochemistry: Grundriss der technischen Elektrochemie auf theoretischer Grundlage ("The Theoretical Basis of Technical Electrochemistry"), which was based on the lectures he gave at Karlsruhe. In the preface to his book he expressed his intention to relate chemical research to industrial processes and in the same year he reported the results of his work on electrolytic oxidation and reduction, in which he showed that definite reduction products can result if the potential at the cathode is kept constant. In 1898 he explained the reduction of nitrobenzene in stages at the cathode and this became the model for other similar reduction processes.

There followed, during the next ten years, many other electrochemical researches. Among these was his work on the electrolysis of solid salts (1904), on the establishment of the quinone-hydroquinone equilibrium at the cathode, which laid the foundations for Biilmann's quinhydrone electrode for determining the acidity of a liquid. Haber invented, in collaboration with Cremer, the glass electrode for the same purposes which is now widely used. This led Fritz Haber to make the first experimental investigations of the potential differences that occur between solid electrolytes and their aqueous solutions, which were of great interest to physiologists.