Supercrit. fluids (SCFs) were intensively studied in the last decade as alternative, environment-friendly benign reaction solvents. A new anal. technique was derived from a combination of classical heat flow reaction calorimetry and the supercrit. fluid technol., namely supercrit. reaction calorimetry. When using SCFs, the internal heat-transfer coeff. decreases with increasing temp. Thus, there is a distinct limit to the heat that can be dissipated. A compromise must be made between a high reaction temp., where the reaction is faster but less safe, and a low reaction temp., where the reaction is slower but within safety limits in terms of heat removal.