Potassium Iodide for Use as a Primary Standard

Potassium hydrogen fluoride, 1 140 Potassium iodide, for use as a primary standard, 1 163 Potassium metaperiodate, 1 171 Potassium molybdoeyanide dihydrate, 3 160... 

Potassium iodate is used as a primary standard for thiosulfate solutions in quantitative analysis. Iodate reacts quantitatively with iodide to produce iodine, as shown in Equation (18.43) ... 

Although sodium oxalate is commonly used as a primary standard, its use is recommended only when oxalate is to be determined. For best absolute accuracy As(III) oxide is recommended. The direct titration of As(III) in acid solution does not proceed readily without a catalyst, probably because of the stabilization of Mn(III) by complex formation with As(V). With potassium iodate (1 drop of0.0025 M solution) as catalyst, the potentiometric end point was found to coincide with the visual end point, using ferroin, to within 0.01%, and the accuracy, tested against pure potassium iodide, was within 0.02%. 

Potassium bromate in the purest commercial product is >99% pure. When the powder is dried at 120°C for 2 hours can be used as a primary standard, llie solution can be titrated after oxidising iodide to iodine as above. 

Standard 1/10 N nitrite is used to titrate a solution prepared by dissolving 10—100 mg of sulfamic acid and about 6 mL of (1 + 1) H2SO4 in 300 mL of distilled water at 40—50°C. At the end point, the colorless external potassium iodide starch-paste indicator changes to blue. A 1-mL solution of 1/ION NaN02 is equivalent to 9.709 mg of sulfamic acid. The 1/10 N nitrite titrant solution is standardized using primary standard-grade sulfamic acid. For sulfamate assay determination, the same procedure is used as for sulfamic acid. 

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