QUANTITATIVE DETERMINATION OF TOTAL HARDNESS IN DRINKING WATER BY COMPLEXOMETRIC EDTA TITRATION

KENT HARRY P. CUMPIODEPARTMENT OF CHEMICAL ENGINEERING, COLLEGE OF ENGINEERINGUNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY, PHILIPPINESDATE PERFORMED: DATE SUBMITTED: MAY 12, 2014MR. MOISES JEROME GARRERO

ABSTRACT

INTRODUCTIONIn the industrial setting, one of the considerations for equipment use is water hardness. This indicates the level of calcium and magnesium present in the water sample. A high level of hardness can pose damages and incur high costs on a company through blockage of pipes, for example. The hardness of water can be determined by complexometric titration using ethylenediammine tetra acetic acid (EDTA). EDTA in the form of its di-sodium salt can form a complex with Ca2+ and Mg2+ ions of water sample. In this experiment, Eriochrome Black T will be used as the indicator. Its uncomplexed color is blue while its complexed color is red. When Eriochrome Black T (EBT) indicator is added to the hard water at pH around 910, it gives wine red colored unstable complex with Ca2+and Mg2+ions of water sample. When this wine red colored complex is titrated against EDTA solution of known strength the Ca2+and Mg2+ions form stable metal complex with EDTA and color changes from wine red to blue (color of EBT indicator) at the end point. In this experiment, two sets of samples were titrated with EDTA: calcium carbonate solution for standardization and Viva mineral water samples. The primary objective was to apply the concept of complexometric titration and buffers in establishing the truthfulness of the advertised cationic levels. METHODOLOGYThe EDTA titrant needed had a molarity of 0.0050. This was prepared from a 500-mL of 0.050 M stock EDTA solution. Two parts of the experiment that required this were the standardization of 0.01 M EDTA and the analysis of a commercial drinking water sample. To standardize EDTA, 0.0050 M calcium carbonate which was dissolved in water and hydrochloric acid was used. Before beginning the titration, a buffer composed of ammonium chloride and ammonia maintained the pH at the desired level and 6 drops of Eriochrome Black T was placed to determine the endpoint. The solutions were titrated slowly before approaching the endpoint to avoid overtitration. RESULTS AND DISCUSSION

CONCLUSION AND RECOMMENDATION

REFERENCES

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