Research on Thermal Decomposition of BORAX. I. Research on Borax (Na2B4O5 (OH)4) multiplied by (times) 8H2O.

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 behavior of glass. From this glass sodium diborate (Na//2O multiplied by (times) 2B//2O//3) crystallizes between 500-600 degree with further mass loss. Sodium diborate decomposes from about 700 degree incongruently yielding NaBO//2 vapor and B//2O//3 glass phase. After evaporation of NaBO//2 is completed the rate of evaporation of B//2O//3 increases considerably.