ISO 3238:1975

Sodium sulphate for industrial use — Determination of calcium content — EDTA complexometric method

Applicable to products the Ca content of which exceeds 0.002 % (m/m). Extraction of a test portion with dilute acid and separation of the insoluble residue. Titration of the calcium with standard volumetric disodium ethylenediamine-NNN’N’-tetra-acetate dihydrate (EDTA) solution in the presence of glyoxal-bis(hydoxy-2-anil) as indicator.