Dear Sirs,

According to Weil et al., 2003 protocol for the preparation of 0.2M KMnO4 stock solution we should:

· Weigh 31.60 g of KMnO4 into a 1000 mL beaker and add approximately 900 mL of the CaCl2 solution. Place on the magnetic stir plate with gentle heat and stir until dissolved c

· Once dissolution is complete, place the probe from a calibrated pH meter into the solution (with continued stirring) and measure the pH. Adjust the pH to 7.2 by adding 0.1 N NaOH, 1 drop at a time.

However pH meter gives me values much higher than 7.2 for the KMnO4 /CaCl2 solution. Why then is it proposed adjustment by NaOH which will make my solution pH even more basic ?

Is it something wrong with my reagents or any one else had a similar issue ?

Many thanks,


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