Abstract: An industrial process is one for the economic production of boric acid and sodium hydroxide or a sodium salt, from sodium borates. Boric acid solution, sodium hydroxide solution, oxygen and hydrogen gases are produced by the electrolysis of sodium borate solutions. Mercury cathode and cation exchange membrane methods have been applied to the electrolysis of sodium borate solutions and, for the economical production of pure boric acid and sodium hydroxide, it was confirmed that the working temperature must be between 60.degree.-100.degree. C., working voltage must be 3.5-5.0 volts, Na.sub.2 O/B.sub.2 O.sub.3 mole ratio at the end of the electrolysis must be 0.15-0.05 and the crystallization temperature must be between 5.degree.-40.degree. C.