Abstract: An autoclave useful for pressure digestion of samples for chemical analysis, consisting of a closeable vessel containing the sample, which during operation sustains elevated temperatures and pressures. The autoclave has a PTFE (Teflon) beaker and lid, in direct contact with each other thus forming a tight seal with an excess-pressure release mechanism. The assembled vessel is held in a device that presses the sealing surfaces of the beaker and lid together, through pressure on a metallic lid support disc. The sealing surfaces of the beaker and lid are free-standing, which permits a direct release of excess-pressure and necessitates an extended clamping device for the lid support disc, which is fixed at a single point.