An Isoteniscope is a measuring device used to measure the vapor pressure of liquids. It consists of a submerged manometer and container holding the substance whose vapor pressure is being measured. The open end of the manometer is then connected to a pressure measuring device. A vacuum pump is used to adjust the pressure of the system and purify the sample.

Various ASTM vapor pressure measurement standards use the isoteniscope.^[1][2] Dr. Bertrand of the Missouri University of Science and Technology offers an interactive animation of a lab procedure using the isoteniscope on his web page.^[3]