The solution calorimeter described previously [Rev. Sci. Instr.26, 477 (1955)] has been modified by using an electrically heated shield for the adiabatic control. In this way the response time has been decreased by a factor of ten which greatly facilitates operation of the control. Under steady conditions the fluctuation in temperature between the calorimeter and its surroundings has been reduced from ±0.002 to ±0.001°C max. The calorimeter has a working range of 10° to 50°C.