Method of purifying thiocyanate solutions

Claim 1

A METHOD OF PURIFYING AN IMPURE DILUTE AQUEOUS SODIUM THIOCYANATE SOLUTION, FORMED IN SYNTHETIC FIBER SPINNING, TO A DEGREE OF PURITY SUCH THAT AFTER CONCENTRATION IT CAN BE USED AS THE SOLVENT COMPONENT OF A SPINNING SOLUTION THAT WILL NOT OBSTRUCT SPINNERETTE OPENINGS BY DEPOSITING IMPURITIES THEREIN, WHICH COMPRISES EVAPORATING WATER IN A SINGLE HEATING STEP FROM AN AQUEOUS 2% TO 20%, BY WEIGHT, SODIUM THIOCYANATE SOLUTION FROM SAID SOURCE HAVING A PH OF AT LEAST 7.5 AND CONTAINING SMALL AMOUNTS OF SODIUM SULFATE AND COLOR-FORMING METALLIC COMPOUNDS AS IMPURITIES UNTIL THE SOLUTION CONTAINS BETWEEN ABOUT 56% AND ABOUT 62% BY WEIGHT OF NASCN AND THAT PART OF THE SODIUM SULFATE WHICH IS IN EXCESS OF THE SOLUBILITY OF NA2SO4 IN THE SOLUTION AFTER CONCENTRATION HAS PRECIPITATED, TRANSFERRING THE RESULTING CONCENTRATED SODIUM THIOCYANATE SOLUTION IN A PRECIPITATEFREE CONDITION TO A COOLING ZONE, COOLING IT IN SAID ZONE TO A TEMPERATURE BELOW 38*C. BUT ABOVE THE FREEZING POINT OF THE CONCENTRATED THIOCYANATE SOLUTION AND MAINTAINING IT AT SAID TEMPERATURE UNTIL SUBSTANTIALLY ALL OF THE RESIDUAL SODIUM SULFATE HAS SEPARATED THEREFROM, THE AFORESAID COLOR-FORMING METALLIC COMPOUNDS BEING REMOVED IN INSOLUBLE FORM FROM THE SODIUM THIOCYANATE SOLUTION ALONG WITH THE SODIUM SULFATE BY REASON OF ITS ALKALINE CONDITION.

Claim 2

A METHOD OF PURIFYING AN IMPURE DILUTE AQUEOUS SODIUM THIOCYANATE SOLUTION, FORMED IN SYNTHETIC FIBER SPINNING, TO A DEGREE OF PURITY SUCH THAT AFTER CONCENTRATION IT CAN BE USED AS THE SOLVENT COMPONENT OF A SPINNING SOLUTION THAT WILL NOT OBSTRUCT SPINNERETTE OPENINGS BY DEPOSITING IMPURITIES THEREIN, WHICH COMPRISES EVAPORATING WATER IN A SINGLE HEATING STEP FROM AN AQUEOUS 2% TO 20%, BY WEIGHT, SODIUM THIOCYANATE SOLUTION FROM SAID SOURCE HAVING A PH OF AT LEAST 7.5 AND CONTAINING SMALL AMOUNTS OF SODIUM SULFATE AND COLOR-FORMING METALLIC COMPOUNDS AS IMPURITIES UNTIL THE SOLUTION CONTAINS BETWEEN ABOUT 56% AND ABOUT 62% BY WEIGHT OF NASCN AND THAT PART OF THE SODIUM SULFATE WHICH IS IN EXCESS OF THE SOLUBILITY OF NA2SO4 IN THE SOLUTION AFTER CONCENTRATION HAS PRECIPITATED, TRANSFERRING THE RESULTING CONCENTRATED SODIUM THIOCYANATE SOLUTION IN A PRECIPITATEFREE CONDITION TO A COOLING ZONE, COOLING IT IN SAID ZONE TO A TEMPERATURE BELOW 38*C. BUT ABOVE THE FREEZING POINT OF THE CONCENTRATED THIOCYANATE SOLUTION AND MAINTAINING IT AT SAID TEMPERATURE UNTIL SUBSTANTIALLY ALL OF THE RESIDUAL SODIUM SULFATE HAS SEPARATED THEREFROM, THE AFORESAID COLOR-FORMING METALLIC COMPOUNDS BEING REMOVED IN INSOLUBLE FORM FROM THE SODIUM THIOCYANATE SOLUTION ALONG WITH THE SODIUM SULFATE BY REASON OF ITS ALKALINE CONDITION.