Modern high-pressure-high-temperature methods, mainly developed within the last twenty years, have vastely extended the pressure-temperature-region for synthesis work from pressure of about 1000 atm. at temperatures up to 0 500 C twenty years aga to some 100000 atm. and temperatures weH above 0 4000 C today. Thus a broad promising /ield 0/ experimental research has been opened out for science and technology. An incentive to the development of these new experimental techniques has been the diamond synthesis which after it was first achieved in 1953/54 (Gen. EI. Comp.; Norton Comp.; ASEA) has since been taken up by numerous other research groups and which has already been applied industrially to a certain extent. In detail: I. The basic phase equilibria of the diamond synthesis and the problems connected with the transformation curve graphit -+ diamond were discussed, and on this basis the experimental conditions of the hitherto secured syn- theses were criticaHy reviewed. H. The construction principles, materials and measuring techniques of the new synthesis equipments were discussed as the main items of the new high- pressure-high-temperature methods. Special interest was shown in the auto- clave construction and material as weH as in the methods for measuring extremely high pressures. III. The construction principles of the most important high-pressure-high- temperature-apparatus were expounded, viz. the "Belt" of the Gen. EI. Comp. as an example of a 2-piston-autoc1ave, the ASEA 6-piston-autoc1ave, the Hall 4-piston-tetraeder-autoclave and the Norton-Coes universal auto- clave. IV.
