A bstract A phase‐equilibrium diagram of the system BaO–B 2 O 3 has been constructed from data obtained essentially by the quenching method. Four congruently melting compounds were identified: BaO·4B 2 O 3 , melting at 879 ± 5°C.; BaO·2B 2 O 3 , melting at 900 · 5°C.; BaO·B 2 O 3 , melting at 1095 ± 5°C.; and 3BaO·B 2 O 3 , melting at 1383 ± 5°C. Some optical properties of these compounds were determined with the petrographic microscope, and X‐ray diffraction data suitable for their identification were obtained. Barium metaborate, BaO·B 2 O 3 , showed an inversion occurring between 100° and 400°C. Mixtures containing less than 30% BaO were found to separate, on fusion, into two liquid layers; one layer contained 30% BaO and the other was nearly pure B 2 O 3 . A curve showing indices of refraction of the quenched glasses is presented.
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Levin et al. (1949) studied this question.