Thermal Changes Accompanying the Compression of Aqueous Solutions to Deep‐Sea Conditions1

Abstract

Apparatus is described for studying the effects of high hydrostatic pressure on the viability, reproduction, and physiological reaction rates of bacteria in aqueous solutions. Rapidly compressing such solutions to deep‐sea conditions results in temperature increases ranging from 2 to 5°C. Decompressing the system to ambient pressure results in cooling to a corresponding degree. When the apparatus is submerged in constant temperature water bath, the thermal time constant T‐63 of solutions compressed or decompressed in the steel pressure vessel is generally less than 3 minutes. The degree of heating or cooling is primarily a function of the change in hydrostatic pressure and the ambient temperature. To a lesser extent heating or cooling is influenced by the chemical composition of the solution. The degree and duration of thermal changes may be minimized by the use of small pressure vessels submerged in constant temperature bath and by slow compression or decompression. Thermal changes were measured by bead‐type thermistors, which must be calibrated for use at each pressure and ambient temperature.