Question #51216

Discuss the Hittorf method of determination of transport number.

Expert's answer

The concept of transport number or transference number was introduced by Johann Wilhelm Hittorf in 1853. Liquid Junction Potential can arise due to ions in a solution having different ion transport numbers. The Hittorf method is an experimental technique for the determination of transport numbers. For the simplest case of a solution of a single salt of univalent ions, the transport numbers are defined as the mobility of the ion divided by the sum of mobilities of the two ions. If there are more than one solutes present (e.g., an acidified sodium chloride solution or a mixture of sodium chloride and potassium bromide), every ion will have its own transport number with the sum of them being unity. In these cases, the concentrations of the ions must also be taken into account in the calculation of the transport numbers, and in the case of polyvalent ions, the charges of the ions must also be accounted for.

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