Probertite (NaCaB(5)O(9)center dot 5H(2)O) and ulexite (NaCaB(5)O(9)center dot 8H(2)O) Posses identical chemical formula except for their water content. In this study, the dissolution of probertite in boric acid solution was investigated as a function of temperature and time. As the boric acid concentration increased, the dissolution of probertite also increased. However, the boric acid concentrations above 5 wt.% at 60 degrees C and 80 degrees C did not significantly affect the dissolution of probertite. The stirring speed had almost no effect on the dissolution of probertite. The dissolution kinetics of probertite in boric acid solution was controlled by first order pseudo homogeneous reaction. The activation energies for different probertite particle sizes varied from 25.25 kJ/mol K to 28.25 kJ/mol K, indicating that particle size had minor effect on the dissolution of probertite. (C) 2008 Elsevier B.V. All rights reserved.