Solution calorimetry is a method for finding the total heat produced during a cement hydration process, e.g. during 3 or 7 days of hydration. In the method samples are dissolved in a mixture of hydrofluoric and nitric acids in a Teflon-coated Dewar flask (a semi-adiabatic calorimeter) and the temperature increase is measured and converted to heat release (cf. semi-adiabatic calorimetry above). The difference between the heat produced when an unhydrated cement and a hydrated cement paste are dissolved in the acid (to the same completely dissociated condition) is the heat produced during the hydration. Solution calorimetry can only be used for cement paste and the procedure with strong acids is today surrounded by workers safety regulations, making it a difficult method to use. A potential problem with solution calorimetry is that it does not work well if the acids do not dissolve the cement powder and the hydrated cement to the same state. There are some cements with which this method does not work well. Solution calorimetry is an old standard method, e.g. ASTM C186 and prEN 196-8 (CEN 1994). In this project solution calorimetry was run by Cementa Research AB in Slite, Sweden.