A series of paper reprinted from The Chemical Engineer presented at a symposium on sealing against pressure and vacuum. These include 'Some Experience in the Application of Mechanical Seal to Pumps and Stirred Pressure Vessels' by V.J. Osola, 'High Pressure Joints' by W.R.D. Manning, 'The Fundamental Factors Influencing Tightness in the Design of Stop Valves' by H.E. Charlton and 'High Vacuum Closures' by A.W. Avery.