A study of the solubility in the ternary systems NaBH4–NaOH–H2O, KBH4–KOH–H2O, NaOH–NaBO2–H2O и KOH–KBO2–H2O is of special fundamental and practical interest. The first two systems are used as a fuel and as a hydrogen source in hydrogen power engineering that includes the low-temperature fuel cells; borohydrides are converted into metaborates. Hence, the last two systems represent the discharged by-product.
