Method of producing sodium tetrahydroborate with boron isotope 10B

Sodium tetrahydroborate is used for the synthesis of substituted higher boranes with isotope 10B which are used in the neutron therapy of malignant tumors. The patented methods allows to prepare pure sodium tetrahydroborate without loss of the initial boron compound. The principle of the preparation consists in that in the presence of benzene or toluene, sodium tetrahydrido-aluminate reacts with at a molar ratio of 1.33 to 1.75 : 1. The reaction best proceeds in a benzene medium and at boil. The produced insoluble sodium tetrahydroborate is pure and easy to separate by filtration. Examples are given of the preparation of sodium tetrahydroborate with yields of 97.1 to 99.96%. (E.S.)