Transference numbers of concentrated manganous chloride solutions

Electrolytic conduction differs from metallic conduction only in the nature of the carrier of the current. In the case of metallic conduction the carrier is electrons. The passage of an electric current through an electrolyte occurs only by the movement of ions of opposite charge moving in opposite directions under an applied potential. The current carried by a particular ionic species is a direct function of the concentration, the charge on the ion, and the ionic mobility. A transference number is the fraction of the total current a given ion carries in a particular electrolyte undergoing electrolysis. The sum of the transference numbers of all the ions present in a solution must therefore add up to unity. Transference numbers are involved in many physical chemical considerations. Calculation of ionic mobility, equivalent ion conductivities, dissociation of electrolytes, effective ion “diameters,” hydration, and the electromotive force of concentration cells involve transference numbers. The presence of complex ions can be detected in solutions by the appearance of “abnormal” or negative transference numbers. At present there are three practical methods of experimentally determining transference numbers: the electromotive force, the moving boundary, and the analytical Hittorf. The advantage of the first is speed, but it is based on rather tenuous assumptions. The moving boundary method gives high precision results, but it is useless at concentrations above one molar. Therefore, the analytical Hittorf method was used in this investigation. The objectives of this investigation were: (1) to determine transference numbers in solutions of one molar concentration and stronger; (2) to design and construct a suitable constant voltage source; (J) to assemble and make operative a coulometer for the precise measurement of faradays; (4) to determine the cation transference number of one molar potassium chloride using Findlay transference tubes and the Hittorf method, and to compare with accepted values found in the literature; (5) to find the cation transference number of manganous chloride at concentrations of on molar and higher --Introduction, pages 1-2