This work is based on the Applied Potential Tomography (APT) system developed in Sheffield and the results specifically relate to this system. Using a cylindrical phantom containing saline, the effects of extended layers in the third dimension on the two-dimensional tomographic images have been studied. Experimentally obtained magnitudes of pixel values corresponding to different conditions in the third dimension are presented. Analysis of these data brings out two phenomena: (i) layers of changed resistivity out of the electrode plane can appear as both increased and decreased resistivity in the image; and (ii) the position of the maximum resistivity change in the image occurs at increasing distances from the edge of the phantom, as the layers of resistivity change are introduced further from the electrode plane and they have a one to one relationship. An intuitive interpretation related to perturbation of equicurrent surfaces in the third dimension has been suggested to explain these phenomena.

The electrochemical redox behavior of transition metal ion Co2+ at different pH in acetate buffer solution has been investigated using cyclic voltammetry and differential pulse voltammetry at glassy carbon electrode (GCE). In cyclic voltammograms (CVs), Co2+ shows a pair of cathodic and a pair of anodic peak. The peak potential separation and peak current ratio reveals that the redox process of the redox couples, Co2+/Co+ and Co+/Co followed a quasi-reversible behavior and are two step one-electron transfer processes. The electrochemical processes are diffusion controlled. The nature of CV of Co2+ has greatly influenced by the potential scan rate and solution pH. With increasing scan rate both cathodic peaks shifted towards negative potential and first cathodic peak was eventually diminished. In the reverse direction, unexpected behavior such as distinguishable second anodic peak, identical heights of two anodic peaks, three humps like peaks and finally domination of second anodic peak were noticed. However, in lower pH all the above mentioned behavior appeared with higher scan rate. While at higher pH of the solution the peculiar behavior was found at lower scan rate. Nevertheless, at pH 6.5, it demonstrated intense cathodic peaks and a very large anodic peak at all scan rates. Dhaka Univ. J. Sci. 65(2): 107-112, 2017 (July)