Hittorf, Johann Wilhelm

Three experimental methods have been employed for the determination of transport numbers. One of them, developed by the German physicist Johann Wilhelm Hittorf (1824-1914) in 1853, involves measuring the changes of concentration in the vicinity of the electrodes. In the second, the moving boundcny method a study is made of the rate of movement, under the influence of a current, of the boundary between two solutions. This method is described on p. 283. A third method, which we will not consider in this book, involves the measurement of the electromotive force of certain electrochemical cells. 

Faraday had worked out the laws of electrolysis, and from those laws it had seemed that electricity, like matter, might well exist in the form of tiny particles (see page 90). Faraday had spoken of ions, which might be considered as particles carrying electricity through a solution. For the next half century, however, neither he nor anyone else had ventured to work seriously on what the nature of those ions might be. This did not mean, however, that no valuable work was done. In 1853, the German physicist Johann Wilhelm Hittorf (1824-1914) pointed out that some ions traveled more rapidly than others. This observation led to the concept of transport number, the rate at which particular ions carried the electric current. But even calculation of this rate still left the nature of ions an open question. 

Figure 21.13 shows the experimental setup of a special electrolytic cell introduced by the German physicist Johann Wilhelm Hittorf. One platinum sheet serves as the cathode and one serves as the anode. After a given duration of electrolysis, the stopcock is closed and the solutions from both the anode compartment and cathode compartment are drained off and then titrated. Subsequently, the transport numbers can be determined from the reduction of concentration in both electrode compartments (so-called Hittorf method). 

Nevertheless, in the 1850s, Johann Wilhelm Hittorf published a series of papers, of which the first [3] was translated to English ( On the migration of ions during hydrolysis ) and reprinted in 1899 [4]. This collection of papers [4] written by Faraday, Hittorf, and Kohlrausch (all in English) is a very inspiring source of information about the early investigations on electrolytes so closely related to electrochemistry. 

The transport number is a measurable value using a variety of weU-developed methods [1], One of the most popular methods is using a Hittorf ceU [1]. Johann Wilhelm Hittorf introduced his transport cell in 1853. Equation 3.17 is the background for estimating the ionic conductivities tabulated in [Chapter 10, Table 10.12] as soon as the transport numbers are experimentally measured. 

Johann Wilhelm Hittorf (1824-1914) was a German physicist who contributed to the theory of ionic transport in electrolyte solutions due to migration of the oppositely charged ions to anode and cathode. He introduced the ion transport numbers and the first method for their measurments. 

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