DIN EN 12829:2011-07

This document specifies a method of preparing water of known calcium and magnesium hardness for use in testing surface active agents and products containing them. The stock solutions are prepared by dissolving an appropriate quantity of calcium chloride or magnesium chloride in water. The calcium or magnesium ions in this stock solution are determined by complexometric titration with the disodium salt of (ethylenedinitrilo)tetraacetic acid (EDTA) using a mixture of Mordant Black 11 (C.I. 14645) and methyl red as indicator. Dilute solutions of the hardness required are prepared by dilution of appropriate volumes of the stock solution. This document (DIN EN 12829:2011) has been prepared by CEN/TC 276 "Surface active agents", the secretariat of which is held by AFNOR (France). The responsible German committee is Working Committee NA 062-05-63 AA "Anwendungstechnische Prüfverfahren für Tenside" ("Application technology test methods for surfactants") of the Materials Testing Standards Committee (NMP) at DIN.