Abstract: Liquid rheostat system especially a water rheostat, employing the principle wherein electrical energy may be dissipated in the form of heat, by passing the electrical current through a liquid resistor or electrolyte, and wherein the apparatus is reasonably portable, inexpensive, and economical to operate and maintain. The invention readily compensates in use for variations in respective resistivity of fresh and/or brackish waters in a test mixture whereby to provide sufficient initial resistance as well as an adequate range of control of resistance, while maintaining current density within the desired limits. In use the heat energy developed is absorbed and removed by the controllable water mixture which in operation of the rheostat system continuously flows out of the rheostat.