Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Hydrogen Diiodate (Potassium Bi-iodate) Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for Potassium Hydrogen Diiodate provides, in addition to common physical constants, a general description including typical appearance, applications, and aqueous solubility. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, Assay, Insoluble Matter, Chloride, Sulfate, Heavy Metals, and Iron.
KH(IO3)2
Formula Wt 389.91
CAS No. 13455-24-8
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . standardizing bases Aqueous solubility . . . . . . . . . . . . . . . . . . . . 1.3 g in 100 mL at 15 °C
SPECIFICATIONS Assay (acid–base titrimetry) . . . . . . . . . . . . . . 99.95–100.05% KH(IO3)2 Assay (iodometric). . . . . . . . . . . . . . . . . . . . 99.9–100.1% KH(IO3)2
Insoluble matter . . . Chloride (Cl) . . . . . Sulfate (SO4) . . . . . Heavy metals (as Pb) Iron (Fe) . . . . . . . .
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© 2017 American Chemical Society
Maximum Allowable 0.01% 0.02% 0.005% 0.001% 0.001%
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DOI:10.1021/acsreagents.4290 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Note: Both assay procedures represent common uses of this reagent. The sample should be thoroughly crushed and dried for 1 h at 105 °C before use in either assay procedure.
Assay (By acid–base titrimetery). Weigh in duplicate (to the nearest 0.1 mg) 1.980 ± 0.001 g of dried sample. Dissolve in 150 mL of carbon dioxide-free water. Add 0.610 g of NIST standard tris(hydroxymethyl)aminomethane (TRIS), stir, and titrate potentiometrically with a solution containing 1 mg of NIST standard TRIS per mL to a pH of 5.00. Calculate the assay value of the sample as follows:
where V = volume, in mL, of TRIS titrant solution; C = concentration, in mg/mL, of TRIS titrant solution; A = weight, in mg, of solid TRIS added; and F = assay value of NIST standard TRIS (÷100).
Assay (By iodometric titration of oxidizing power). Weigh accurately about 0.13 g of dried sample, and dissolve 100 mL of water in a glass-stoppered conical flask. Add 3.0 g of potassium iodide and 1 mL of sulfuric acid. Stopper, swirl, and let stand for 30 min. Titrate the liberated iodine with 0.1 N sodium thiosulfate volumetric solution, and add 3 mL of starch indicator solution near the end of the titration. Correct for a blank. One milliliter of 0.1 N sodium thiosulfate corresponds to 0.003249 g of KH(IO3)2.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 10.0 g dissolved in 200 mL of water.
Chloride Dissolve 1.0 g in 100 mL of water in a conical flask, filter if necessary through a chloride-free filter, and add 6 mL of hydrogen peroxide and 1 mL of phosphoric acid. Heat to boiling, and boil gently until all the iodine is expelled and the solution is colorless. Cool, wash down the sides of the flask, and add 0.5 mL of hydrogen peroxide. If an iodine color develops, boil until the solution is colorless and then for an additional 10 min. If no color develops, boil for 10 min. Dilute with water to 100 mL, and dilute a 10 mL portion to 25 mL. Prepare a standard containing 0.02 mg of chloride ion (Cl) and 0.6 mL of hydrogen peroxide in 23 mL of water. Add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution to each. Any turbidity in the sample solution should not exceed that in the standard.
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 2]. Evaporate 1.0 g to dryness with 3 mL of hydrochloric acid, and repeat the evaporation three additional times. Allow 30 min for turbidity to form.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4290 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Heavy Metals Treat 10.0 g with 10 mL of hydrochloric acid, and evaporate to dryness. Repeat the evaporation two additional times. Dissolve the residue in water, and add 1 mL of 1 N acetic acid and 5 mL of hydrogen sulfide water. For the standard, use 0.1 mg of lead ion (Pb) treated exactly as the sample. Any brown color produced in the sample solution within 5 min should not exceed that in the standard.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 2 (Hydroxylamine and 1,10-Phenanthroline)]. Treat 1.0 g with 1 mL of 50% sulfuric acid and 5 mL of hydroxylamine hydrochloride reagent solution. Evaporate to expel the iodine. Dissolve the residue in 10 mL of water, and add 1 mL of hydroxylamine hydrochloride reagent solution.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4290 ACS Reagent Chemicals, Part 4
