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Fill the Erlenmeyer flask (1) with approx. 30 ml test solution up to the mark. Add exactly 2 ml of flux using the small syringe (5). Draw exactly 10 ml of titration solution (3) bubble-free into the large syringe (4) and drip it very slowly into the test solution.
slowly to the test solution in the Erlenmeyer flask (Fig. 2), which is swirled from time to time to ensure good mixing. Initially, a blue-green to violet colour develops where the titration solution drips in, which disappears again during mixing (Fig. 3). Continue dripping until a colour change to pale green occurs in the entire solution (Fig. 4-5); keep mixing in between. This is an indication that the end point of the titration will soon be reached. If the colour finally changes to light blue (Fig. 6), the end point has been reached and the amount of titration solution used can be read off the syringe. A further addition results in a blue to dark violet colour (Fig. 7-8) and you have over-titrated. The measurement is repeated to rule out the possibility of an erroneous result.