Concentrated water-alkaline mixtures of sodium and potassium borohydrides and borates are used as fuel and a hydrogen source in hydrogen power engineering, including low-temperature fuel cells. The performance of such mixtures is determined by their physicochemical properties. An algorithm to calculate the density, viscosity, and specific electric conductivity of mixed solutions of the five-component water + salt system (Na,K)BH4 + (Na,K)BO2 + (Na,K)OH + H2O based on the quasiadditivity of these properties is proposed.
