Oxygen difluoride reacts with cold water extremely slowly. Mixtures of oxygen difluoride and hydrogen form are explosive. It is considerably more dangerous than fluorine in its physiological behaviour. Oxygen difluoride is prepared by reacting elemental fluorine with a dilute aqueous solution of sodium or potassium hydroxide, according to the reaction: 2NaOH + 2F2 => OF2 + 2NaF + H2O. Only 50 per cent of the original fluoride, at best, is recovered as the oxygen difluoride. Thus, it appears that the manufacture of oxygen difluoride is likely to be more costly than fluorine. In 1959 there was no commercial production of OF3 in the United States.