Abstract: A system for automatically and continuously measuring the zinc and sulfuric acid concentration in an electrolyte circulating through electrolysis cells of a hydrometallurgical zinc production system, in which an inductive solution analyzer capable of continuously detecting the conductivity of the circulating electrolyte is used with a measuring cell disposed in the path of a continuous stream of the circulating electrolyte. The measuring cell comprises a defoaming chamber, a measuring chamber and an overflow chamber, and the continuous stream of the electrolyte flows through the measuring chamber as a downward stream so that bubbles can be removed and precipitation of slurry can be prevented. The signal representative of the detected conductivity is applied to an electronic computer which computes automatically the zinc and sulfuric acid concentration according to predetermined calculation formulas.

Abstract: An apparatus for automatically cleaning the electrodes of a pH meter comprising a measuring tank containing a sample solution supplied from a tank of purification section to be subject to measurement of the pH value, a cleaning tank juxtaposed with the measuring tank and having therein a cleaning brush mounted on a rotary shaft, means for supporting the electrodes of the pH meter for vertical movement, and means for supporting the electrodes supporting means for horizontal swinging movement, whereby the electrodes of the pH meter can be moved between the pH value measuring position in the measuring tank and the position engaged by the cleaning brush in the cleaning tank.

Abstract: A method and apparatus for judging the purity of a purified zinc sulphate solution used for the electrolytic production of zinc, which are based on the finding that the purity of the purified electrolyte has a fixed relationship with the ratio between the amount of hydrogen gas and the amount of oxygen gas generated by electrolysis of the purified electrolyte. According to the method and apparatus, a mixture of hydrogen gas and oxygen gas generated by the electrolysis of the purified zinc sulphate solution is charged in a combustion chamber of predetermined volume and ignited by a heater to ignite the hydrogen gas, and the difference between the internal pressures of the combustion chamber before and after the combustion of the hydrogen gas is detected for measuring the hydrogen gas content in the gas mixture.

Abstract: An automatic leaching system for the hydrometallurgical production of zinc comprising a pH meter and means for detecting the feed rate of calcine. The pH meter is provided with means for automatically washing the electrodes thereof so as to be capable of continuously and automatically detecting the pH value of the slurry obtained by mixing a spent electrolyte with the calcine. The system comprises a feedback control circuit and a feed-forward control circuit in which the flow rate of the spent electrolyte supplied to the system is the manipulated variable, and the pH value of the slurry is the controlled variable. These control circuits are used for the pH control so that the pH value of the slurry can be maintained constant by controlling the flow rate of the spent electrolyte.