Untersuchungen zur thermischen Zersetzung von Boraten

In spite of numerous investigations the literature data on the thermal decomposition of borax are contradictory. On the basis of thermal, X-ray, gas analytical and optical investigations this fact can be attributed to the complex decomposition mechanism. After the release of about 8 mole water the reaction product is an X-ray amorphous phase, having the thermal behaviour of glass. From this glass sodium diborate (Na₂O.2B₂O₃) crystallizes between 500–600? with further mass loss. Sodium diborate decomposes from about 700? incongruently yielding NaBO₂ vapor and B₂O₃ glass phase. After evaporation of NaBO₂ is completed the rate of evaporation of B₂O₃ increases considerably.