Quantitative Determination of Total Hardness in Drinking Water by Complexometric Edta Titration

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

R.A. ROGIO

DEPARTMENT OF MINING, METALLURGICAL AND MATERIALS ENGINEERING,

COLLEGE OF ENGINEERING

UNIVERSITY OF THE PHILIPPINES, DILIMAN QUEZON CITY, PHILIPPINES

DATE PERFORMED: JANUARY 31, 2013

INSTRUCTOR’S NAME: MS. MELANIE BUCSIT

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Complexometric EDTA titration was used to determine the mineral content of Viva Mineralized Water. The EDTA solution of 0.050M was first standardized with 99,5% pure calcium carbonate. The environment of the reaction was alkaline, with pH 10 provided by the ammonia-ammonium buffer solution. The metallochrome Eriochrome Black T was used the indicator for this experiment. The same procedures were applied to the analysis of the 50mL aliquot sample. The color changes were expected to be from a wine red (color of EBT bound to a metal ion) to a clear blue solution (color of free EBT ion). The method yielded a hardness of 141.8045 ppm CaCO3 for the group, and 143.598 ppm for the collective data which differ by 26.338% and 25.406%, respectively, with the 192 ppm claim of Viva.

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INTRODUCTION

Minerals dissolved in groundwater produce metal ions such as calcium, magnesium, manganese and iron [1] which are good for the body. Thus, mineralized water or water containing these ions, usually calcium and magnesium, was commercialized. Water containing such ions makes it “hard”. The total hardness of water is defined by the content of calcium and magnesium combined (calcium having the greatest amount present in water compared to the other minerals [2]) in milligrams per liter of water or commonly expressed as ppm CaCO3. Moreover, it is expressed as a combination of the two ions because there is no way to separate the two cations when both present in a solution.

In this experiment, a technique called complexometric EDTA titration was used...