Abstract: An apparatus and process for measuring the percent concentration of an electrolyte in solution is disclosed. The apparatus includes a crystal oscillator generating a square wave and a wave shaper to transform the wave into a monochromatic sine wave which passes through a two stage temperature compensated first buffer amplifier. The sine wave passes between electrodes which project into the solution under investigation and generates an output. A second buffer amplifier operates on the A.C. component of the output from the solution and is operatively connected to a half wave rectifier. The output of the half wave rectifier is proportional to the percent caustic. A temperature control device is utilized to hold the solution at a constant temperature.An alternate embodiment utilizes two identical circuits with two different solutions. One circuit is used with a solution having a known concentration and one with an unknown concentration. The outputs are compared in a differential amplifier.