ISO 2174:1990 Preview
Surface active agents -- Preparation of water with known calcium hardness
This standard was last reviewed and confirmed in 2016. Therefore this version remains current.
A stock solution is prepared by dissolving an appropriate quantity of calcium chloride in water. The calcium content of this stock solution is 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.
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