The Properties of Boron Compounds.
Rept. on aviation fuels,
NATIONAL BUREAU OF STANDARDS GAITHERSBURG MD
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HEATS OF FORMATION OF THE METABORIC ACIDS, by Marthada V. Kilday and Edward J. Prosen Three crystalline forms of metaboric acid exist HBO2C,I, HBO2C,II, and HBO2C,III. Methods of preparing and identifying these 3 crystals and crystals of orthoboric acid H3BO3 are described. The heats of formation of the 3 forms of metaboric acid relative of that of orthoboric acid have been determined by measuring heats of solution of each of the 4 crystals in water and in sodium hydroxide solution. Taking the heat of formation of orthboric acid as Hf25 C 262.16 or - 0.32 kcalmole, the heats of formation of the forms of metaboric acid were found to be HBO2C,I, Hf25 C 192.56 or - 0.40 kcalmole HBO2C,II, Hf25 C 190.6 or - 0.5 kcalmole HBO2C,III Hf25 C -190.0 or - 1.0 kcalmole. DECOMPOSITION PRESSURES OF BORIC ACID, by Edward J. Prosen Decomposition pressure measurements were made on the system H3BO3C H2Og HBO2C,X, where the metaboric acid HBO2 was in the form of HBO2C2,I, HBO2C,II, or HBO2C,III. The results on crystals II and III confirm the data obtained by previous investigators. No previous data existed on crystal I, the most stable form of metaboric acid. From these measurements, heats of formation, free energies of formation, and entropies are derived. Author