The determination of silicon by titration of molybdenum blue with potassium permanganate

• Published in: Bunseki kagaku Vol. 15; no. 4; pp. 347 - 351
• Main Author: ONISHI, Kazuyoshi
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Science and Technology Agency 1966
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.15.347

A method for the determination of silicon has been investigated by means of oxidimetric titration of molybdenum blue. After an addition of 50 ml of 10% ammonium molybdate solution to the sample solution, the mixture is adjusted to pH 1.6 and 2.5 for 10 and 5mg silicon, respectively. Silicomolybdic acid formed is reduced to molybdenum blue that corresponds to the reduced state of two electrons by adding 20 ml of 10% sodium sulfite solution and boiling for 7 minutes. The excess of sulfite is decomposed by increasing the sulfuric acid concentration to 2 N and boiling for 15 minutes. The solution is titrated with 0.05 N potassium permanganate solution until the blue color disappears. The amount of silicon is calculated by the following equation: Si (mg) =0.7022×V where V is the ml of the potassium permanganate solution against the reagent blank. When the pH at the formation of silicomolybdic acid is 2.4 to 2.6, 3 to 6 mg of silicon was determined with coefficients of variation of 0.5 to 2.7%.