Method of purifying sodium hydroxide solutions

Claim 1

A METHOD OF PURIFYING AQUEOUS SODIUM HYDROXIDE CONTAINING 45 TO 60 PERCENT NAOH BY WEIGHT AND SODIUM CHLORIDE AS AN IMPURITY WHICH COMPRISES EXTRACTING, AT A TEMPERATURE OF 140* F. AND A PRESSURE ABOVE 400 POUNDS PER SQUARE INCH, A QUANTITY OF SAID HYDROXIDE WITH AQUEOUS AMMONIA CONTAINING 88% NH3 IN AMOUNT SUFFICIENT TO FORM A LIQUID PHASE WHICH IS PRIMARILLY AMMONIA AND WATER TOGETHER WITH SODIUM CHLORIDE EXTRACTED FROM THE SODIUM HYDROXIDE SOLUTION, AND A SECOND LIQUID PHASE COMPRISING PURIFIED NAOH WATER AND AMMONIA, SEPARATING THE PHASES, REDUCING THE PRESSURE UPON SAID FIRST PHASE TO 150 POUNDS PER SQUARE INCH AND HEATING TO DISTILL THE AMMONIA THEREFROM AT SAID REDUCED PRESSURE, REDUCING THE PRESSURE UPON SAID SECOND PHASE TO 150 POUNDS PER SQUARE INCH AND FLASHING AMMONIA THEREFROM, RELEASING THE PRESSURE UPON THE REMAINING SODIUM HYDROXIDE IN SAID SECOND PHASE AND HEATING TO DRIVE OFF RESIDUAL AMMONIA TOGETHER WITH SOME WATER VAPOR, SCRUBBING THE RESULTING AMMONIA-WATER VAPOR MIXTURE WITH A CONTROLLED AMOUNT OF WATER TO RECOVER THE AMMONIA AS AN AQUEOUS SOLUTION CONTAINING 19 PERCENT BY WEIGHT OF NH3, COMBINING THE EVOLVED AMMONIA FROM THE FIRST PHASE AND THE AMMONIA RELEASED AT 150 LB. PER SQUARE INCH PRESSURE FROM THE SECOND PHASE WITH SUFFICIENT OF SAID AMMONIUM HYDROXIDE SOLUTION TO PRODUCE AQUEOUS AMMONIA CONTAINING 88% BY WEIGHT NH3, AT A PRESSURE OF 150 POUNDS PER SQUARE INCH, CONDENSING THE RESULTING MIXTURE AND RECYCLING SAID

Claim 2

A METHOD OF PURIFYING AQUEOUS SODIUM HYDROXIDE CONTAINING 45 TO 60 PERCENT NAOH BY WEIGHT AND SODIUM CHLORIDE AS AN IMPURITY WHICH COMPRISES EXTRACTING, AT A TEMPERATURE OF 140* F. AND A PRESSURE ABOVE 400 POUNDS PER SQUARE INCH, A QUANTITY OF SAID HYDROXIDE WITH AQUEOUS AMMONIA CONTAINING 88% NH3 IN AMOUNT SUFFICIENT TO FORM A LIQUID PHASE WHICH IS PRIMARILLY AMMONIA AND WATER TOGETHER WITH SODIUM CHLORIDE EXTRACTED FROM THE SODIUM HYDROXIDE SOLUTION, AND A SECOND LIQUID PHASE COMPRISING PURIFIED NAOH WATER AND AMMONIA, SEPARATING THE PHASES, REDUCING THE PRESSURE UPON SAID FIRST PHASE TO 150 POUNDS PER SQUARE INCH AND HEATING TO DISTILL THE AMMONIA THEREFROM AT SAID REDUCED PRESSURE, REDUCING THE PRESSURE UPON SAID SECOND PHASE TO 150 POUNDS PER SQUARE INCH AND FLASHING AMMONIA THEREFROM, RELEASING THE PRESSURE UPON THE REMAINING SODIUM HYDROXIDE IN SAID SECOND PHASE AND HEATING TO DRIVE OFF RESIDUAL AMMONIA TOGETHER WITH SOME WATER VAPOR, SCRUBBING THE RESULTING AMMONIA-WATER VAPOR MIXTURE WITH A CONTROLLED AMOUNT OF WATER TO RECOVER THE AMMONIA AS AN AQUEOUS SOLUTION CONTAINING 19 PERCENT BY WEIGHT OF NH3, COMBINING THE EVOLVED AMMONIA FROM THE FIRST PHASE AND THE AMMONIA RELEASED AT 150 LB. PER SQUARE INCH PRESSURE FROM THE SECOND PHASE WITH SUFFICIENT OF SAID AMMONIUM HYDROXIDE SOLUTION TO PRODUCE AQUEOUS AMMONIA CONTAINING 88% BY WEIGHT NH3, AT A PRESSURE OF 150 POUNDS PER SQUARE INCH, CONDENSING THE RESULTING MIXTURE AND RECYCLING SAID