A new batch microcalorimetric vessel for the determination of enthalpies of dissolution of small amounts of easily or slightly soluble solids was developed at University of Lund, Sweden and was tested at University of Porto, Portugal. The vessel forms part of a series of twin heat conduction microcalorimeters. In a series of consecutive dissolution steps up to four samples, each 0.1-3 mg, can be injected into a solvent chamber of the vessel, volume 20 ml. The high stability of the baseline allows solution experiments to be extended over several hours.All measurements reported were conducted at 298.15 K and with water as the solvent. The calorimeter was calibrated chemically by dissolution of potassium chloride. The performance of the instrument was further tested by measurements of the enthalpies of dissolution of acetanilide and adenine, 18.25 +/- 0.56 and 31.78 +/- 0.64 kJ mol(-1), respectively. No concentration dependence was found. The results are in good agreement with values in the literature. (C) 2003 Elsevier Science B.V. All rights reserved.