A simple, inexpensive spectrophotometric cell was designed for use with aqueous solutions for which temperature is a maximum of 325°C and pressure, 28 MPa. The cell has an internal volume of 5 ml and a path length of 1.31 cm. Each furnace assembly is 120 mm in diameter × 150 mm high and will fit into most commercial spectrophotometers. Temperature is controlled by a standard set‐point controller and a balancing circuit that is used to maintain the temperature of the sample and reference cell within 1°C of each other at any temperature.