Method for making tetra-alkali metal pyrophosphate

Claim 1

IN THE PROCESS OF PRODUCING AN ANHYDROUS TETA-ALKALI METAL PYROPHOSPHATE BY MOLECULAR DEHYDRTION OF A DI-ALKALI METAL ORTHOPHOSPHATE, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID MOLECULAR DEHYDRATION AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 150*C. TO 900*C. IN THE PRESENCE OF FROM ABOUT 0.5 TO 10 WEIGHT PERCENT OF A FLUXING AGENT WHICH WILL FORM A FLUID PHASE IN COMBINATION WITH SAID DI-ALKALI METAL ORTHOPHOSPHATE AT A TEMPERATURE WITHIN SAID TEMPERATURE RANGE, SAID FLUXING AGENT BEING SELECTED FROM THE GROUP CONSISTING OF MONO-ALKALI METAL ORTHOPHOSPHATES, DOUBLE SALTS OF MONO-ALKALI METAL AND DI-ALKALI METAL ORTHOPHOSPHATES, ALKALI METAL ACID PYROPHOSPHATES, ALKALI METAL SULFATES, ALKALI METAL BISULFATES, ALKALI METAL SALTS OF LOWER FATTY ACIDS, MONO-AKALI METAL ARSENATES, ALKALI METAL NITRATES, ALKALI METAL NITRITES, AND AMMONIUM SALTS OF INORGANIC ACIDS SELECTED FROM THE GROUP CONSISTING OF AMMONIUM NITRATE, AMMONIUM PHOSPHATES AND AMMONIUM CHLORIDE, THE TEMPERATURE AT WHICH SAID DEHYDRATION IS CARRIED OUT AND THE AMOUNT OF SAID FLUXING AGENT BEING SUFFICIENT TO CAUSE AN AMORPHOUS PHASE TO FORM AT THE SURFACE OF SAID DI-ALKALI METL ORTHOPHOSPHATE BUT NOT SUFFICIENT TO CAUSE THE ENTIRE REACTION MASS TO BECOME FLUID, THEREBY PRODUCING SAID ANHYDROUS TETRA-ALKALI METAL PYROPHOSPHATE AT A FASTER RATE THAN WOULD HAVE OCCURRED UNDER THE OTHERWISE SAME CONDITIONS IN THE ABSENCE OF SAID 0.5 TO 10 WEIGHT PERCENT OF SAID FLUXING AGENT.