The 4749 is a 23 mL, general purpose acid digestion vessel, similar to the original 4745 model but modified for use at higher temperatures and pressures, and provided with safety blowout protection as well. Operating temperatures and pressures up to a maximum of 250 °C and 1800 psig are permitted in this vessel using a thick-walled PTFE liner with a broad, flanged seal. The forces required to seal the liner are developed by tightening the vessel cap with a spanner while holding the vessel in a special fixture. A safety rupture disc in the vessel head is designed to blow out and release the pressure through an opening in the cover at approximately 3500 psig. With its high temperature capability and safety rupture disc this is an excellent vessel for all general digestion purposes, and particularly for experimental procedures in which the behavior of the reactants has not been well established.