The use of phenolphthalin as a catalytic indicator for the determination of copper and manganese by EDTA titration

• Published in: BUNSEKI KAGAKU Vol. 20; no. 9; pp. 1168 - 1172
• Main Authors: ABE, Shigeki, MATSUO, Tsutomu
• Format: Journal Article
• Language: English; Japanese
• Published: Tokyo The Japan Society for Analytical Chemistry 1971; Japan Science and Technology Agency
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.20.1168

Copper (II) and manganese (II) catalysed the oxidation of phenolphthalin by hydrogen peroxide in an alkaline (pH12) medium and in ammonium carbonate solution, respectively, and the reaction was used to indicate the end point of titration in the determination of Cu and Mn with EDTA. This catalytic titration method was also applied to determine zinc, cadmium and lead by back-titration of excess EDTA with standard copper solution. The results were in good agreement with those by titration using PV or MX as metal indicators. The recommended procedures for copper and manganese were as follows: to an about 50 ml portion of solution containing known amount of EDTA and either phosphate buffer (for Cu) or ammonium carbonate (for Mn), add 1 ml of 0.2% phenolphthalin and 0.5 ml of 0.3% hydrogen peroxide. Titrate the solution with copper or manganese solution. At the end point, the solution turned red immediately by the formation of phenolphthalein. The catalytic effect of metal ions on the oxidation of cresolphthalin was also investigated.