A rapid complexometric scheme for analysis of iron, aluminium, calcium and magnesium in slags

A simple and rapid complexometric method has been developed for the simultaneous determination of iron, aluminium, calcium and magnesium in a single solution in slags. Phosphorous and small amounts of chromium (1.5 mg) and vanadium (1 mg) do not interfere in the titration. Titanium and manganese are suitably masked with lactic acid and tetra sodium pyrophosphate, respectively. In a suitable aliquot, iron is titrated at pH 2 with EDTA, using sulphosalicylic acid as indicator. To this solution, excess disodium 1,2-cyclohexane diamine tetra acetic acid (DCTA) is added and aluminium is titrated by titrating the excess DCTA with standard copper sulphate solution at pH 3.5, using 1-(2-pyridylazo)-2-naphthol (PAN) as an indicator. A known excess of EDTA is added, the pH is raised to 10 and calcium and magnesium are jointly titrated by titrating the excess EDTA with copper sulphate solution, using PAN indicator. The Ca—EDTA complex is demasked with ammonium oxalate at pH 5 and the released EDTA equivalent to calcium is titrated with copper sulphate solution at pH 10 with PAN indicator. Results of analysis compare favourably with certified values and values obtained by standard methods for BCS and other slags. A set of five samples can be analysed for iron, aluminium, calcium and magnesium in four hours as compared to three days by the classical conventional method.