(10)B2O3 was dissolved in H2O, evaporation to dryness at room temp.;;

in toluene byproducts: H2O; (Schlesinger, H. I., et al.; J. Am. Chem. Soc., 1953, v. 75, pp. 216-215); to anhyd. H3(10)BO3 b-BuOH and toluene added; mixt. heated to 130°C over 5 h; distilled at 226-228°C under 1 atm;