METHOD OF PRODUCING POLYPHOSPHORIC ACID Russian patent published in 2011 - IPC C01B25/24 

FIELD: chemistry.

SUBSTANCE: disclosed is a method of producing polyphosphoric acid, involving evaporation of orthophosphoric acid under a vacuum, where evaporation takes place in a multi-mode microwave resonator to temperature 215±5°C for 60-70 minutes at pressure 30-70 mm Hg, while constantly pumping out the formed water vapour and then switching off the microwave generator when the said temperature is achieved.

EFFECT: method increases content of pyrophosphoric acid in polyphosphoric acid, reduces content of higher polyacids, lowers power consumption and enables to obtain colourless polyphosphoric acid which does not contain extraneous impurities without using additives of extraneous substances.

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