Abstract
Two grams of sample are decomposed with 25 ml of perchloric acid. After filtration, a bulk of iron and other heavy metals are removed by mercury cathode electrolysis. Then, the solution is drained and evaporated until the perchloric acid is given off completely. Five milliliters of hydrochloric acid are added to dissolve the residue. After dilution, remaining metals such as iron, aluminum, titanium etc. are precipitated in the form of hydroxide by adding ammonia water. After filtration, the filtrate is made up to 100 ml. Two fifths of the solution is titrated photometrically to determine the sum of calcium and magnesium by using M/500 EDTA and EBT indicator at pH 10±0.2. Another two fifths aliquot is titrated to determine the amount of calcium with M/500 EDTA and NN indicator at pH 12.513. The blank test through the whole procedure is required for the calibration of results. The accuracy of determination of the trace amount of calcium was increased successfully by prescribing on pH range, amounts of coexisting magnesium, indicator blank, standing time after the addition of sodium hydroxide, etc. Trace amounts of calcium and magnesium contained in steel as little as 0.0010.02% were determined within the deviation 0.001%.
