Abstract: An automated vapor pressure measuring apparatus includes an elongated cylindrical casing with a valve therein separating a liquid sample receiving chamber (the liquid chamber) from a vapor decompression chamber (vapor chamber), heaters for heating the chambers separately, temperature probes extending into both chambers, a pressure measuring device connected to the vapor chamber, a device to rotate the cylindrical casing to effect mixing of the contents and a programmable controller for controlling operation of the valve between the chambers, the heaters, valves for introducing and discharging liquid sample from the liquid chamber, and a valve for discharging vapor from the vapor chamber, for monitoring the temperature probes and the pressure measuring device, for controlling the rotating device and for providing visual indications of temperature and pressure.