Process for the manufacture of anhy-

Claim 1

IN THE PROCESS OF MANUFACTURE OF HEAVY METAL-FREE, NAHYDROUS SODIUM SULFITE FROM SODIUM CARBONATE WHEREIN A MAJOR PORTION OF HEAVY METAL IMPURITIES ARE REMOVED FROM SODIUM CARBONATE SOLUTION BY PRECIPITATION AS INSOLUBLE SULFIDES, SAID SOLUTION BEING GASSED WITH SULFUR DIOXIDE TO FORM SODIUM SULFITE SOLUTION FROM WHICH ANHYDROUS SODIUM SULFITE IS CRYSTALLIZED, THE IMPROVEMENT WHICH COMPRISES ADDING TO SAID SOLUTION BEFORE CRYSTALLIZATION OF SODIUM SULFITE A REDUCING AGENT IN AMOUNT SUFFICIENT TO REDUCE RESIDUAL HEAVY METAL IMPURITIES TO LOWER STATES OF OXIDATION, AND ADDING A METAL SALT OF ETHYLENE DIAMINE TETRA-ACETIC ACID IN AMOUNT SUFFICIENT TO SEQUESTER RESIDUAL HEAVY METAL IMPURITIES IN SAID SOLUTION, WHEREBY SAID CRYSTALLIZED ANHYDROUS SODIUM SULFITE IS SNOW-WHITE AND HEAVY METAL-FREE.