Experimental diagnostics to determine the local composition of an aqueous copper sulfate solution

Abstract

Knowledge of solute distribution is required for improved understanding of double‐diffusive phenomena in which transports of heat and species occur simultaneously. The present paper describes an experimental technique to monitor the local composition of an aqueous copper sulfate solution without resort to a sampling procedure. The method is based on the principles of electrochemistry and employs a copper electrode as a sensing probe. Calibration experiments were conducted with the concentration and temperature of a reference solution fixed at 5 wt% and 25°C, respectively. The regressed equation empirically relates the electric potential difference between working and reference electrodes to the concentration and temperature of the solution that contacts the working electrode. During a double‐diffusion experiment, liquid composition can be determined from the measured values of local temperature and cell potential, with the uncertainty smaller than 0.85 mV for the confidence interval of 99.7%. A series of experiments to determine the best method of preparing the copper electrode has also been performed. For the tested diameter of the electrode (0.75 mm), a constant current of 0.4 mA and plating time of 450 s yield minimum offset in electrode potential. © 1999 Scripta Technica, Heat Trans Asian Res, 28(5): 367–378, 1999