Experiments were conducted in a high pressure device consisting of a series of thermostated micro-autoclaves (ID 16 mm, ca. 10 ml). Pressure was generated by a 14 kbar pressure intensifier. The pressure transmitting medium was water. An initial temperature rise due to adiabatic heating (up to 4 C) was usually restored after 1 to 2 min due to rapid heat exchange with the vesselwalls.