Series 4740-4742 High Pressure-High Temperature Pressure Vessels, 25-75 mLThese are the smallest of Parr High Pressure/High Temperature Vessels. They have a 1-inch inside diameter and offer volumes of 25 or 75 mL. These vessels are closed with an alloy steel screw cap which includes six cap screws to develop the sealing force on a flat, flexible graphite gasket. Interchangeable PTFE gaskets are also available for users who need the high pressure capabilities provided by these vessels, but who do not need to operate above 350 °C. Maximum pressure drops quickly at temperatures above 350 °C to a rating of 1850 psi (125 bar) at 540 °C. These vessels are available in all of the standard materials currently offered by Parr, although some of these materials will limit the maximum pressures and temperatures available.