Preparation of highly concentrated aqueous solution of sodium borate

A highly concentrated aqueous solution of sodium borate with 5.24 mol/kg of boron was prepared at 20 degrees C by adjusting the Na/B ratio at 0.22 (pH 6.9). This is more than twice more concentrated than the most soluble known borate solution (Na2O center dot B2O3 center dot 8H(2)O, 2.49 mol/kg at 20 degrees C). Analysis using the Raman spectroscopy and the APCI/MS (atmospheric pressure chemical ionization/mass spectrometry) suggested the formation of polyborate ions such as B9O10(OH)(9)(2-), B10O12(OH)(8)(2-), B11O14(OH)(7)(2-), B12O16(OH)(6)(2-). (c) 2006 Elsevier B.V. All rights reserved.