In this study, it was investigated the optimum conditions (extraction temperature and extraction period) for the production of sodium metaborate dihydrate (NaBO(2 center dot)2H(2)O) by the reaction of ulexite (NaCaB5O9 center dot 8H(2)O) with trona (NaHCO3-Na2CO3 center dot 2H(2)O) and lime (CaO). The optimum extraction conditions were determined as 50 degrees C and higher temperature; 6 h and longer extraction time. The characterizations of the product (sodium metaborate dihydrate crystals) were performed by thermogravimetric (TG-DTG) and X-ray diffraction (XRD) analyses. In addition, the percent purity of the product was found to be 96% by using a conductometric method. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.