ISO 986:1976

Sodium hydroxide for industrial use — Determination of calcium content — EDTA (disodium salt) complexometric method

The method is applicable to products having a calcium content equal to or greater than 0.002 % (m/m). The principle consists in titration of the calcium with a standard volumetric solution of the disodium salt of (ethylenedinitrilo)tetraacetic acid (EDTA disodium salt) in the presence of 2,2′-(ethylenedinitrilo)diphenol ?glyoxal-bis-(2-hydroxyanil)ü as indicator, after elimination of impurities which may hinder the determination. – Replaces ISO Recommendation R 986-1969.