Calcium and magnesium sequestration by sodium and potassium polyphosphates

Abstract

Abstract The sequestration of calcium by polyphosphates in the presence of oxalate as a precipitating agent is reported at 25 and 60C in the pH range of 5–12. Sequestration increased with temperature. The sensitivity of sequestration to pH changes decreased with increase in the chain length of the polyphosphates. Magnesium sequestration by polyphosphates in the presence of sodium oleate is given at pH values of 10.5 and 9.0. In dilute solution with pH values higher than 9.5, tripolyphosphate and pyrophosphate were found to be the most effective calcium and magnesium polyphosphate sequestrants on a weight basis, respectively. The results are discussed from a semi‐theoretical viewpoint.