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Standar Nasional Indonesia

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25 June 2011

Preparation and Standardization of EDTA, 0.1 M

Dissolve 37.22 g of Na2EDTA . 2H2O in 500 mL of water in a 1-L volumetric flask, dilute to mark, and mix thoroughly. Standardize as follows: Weigh accurately 0.40 g of calcium carbonate, chelometric standard, transfer to a 400-mL beaker, and add water. Cover the beaker with a watch glass, and introduce 4 mL of hydrochloric acid (1 + 1) from a pipet inserted between the lip of the beaker and the edge of the watch glass. Swirl the contents of the beaker to dissolve the calcium carbonate. Wash down the sides of the beaker and the watch glass with water, and dilute to 200-mL. While stirring, add from a 50-mL buret about 30 mL of EDTA standard solution. Adjust the solution to pH 12–13 with 10% sodium hydroxide and 300 mg of hydroxy naphthol blue indicator, and continue titration with the EDTA standard solution to a blue endpoint.