Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Iodine 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 Iodine provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), 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, Nonvolatile Matter, Chlorine and Bromine.
I2
Formula Wt 253.81
CAS No. 7553-56-2
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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slate gray to black-violet solid iodometric standard melting point, 114 °C 0.03 g in 100 mL at 25 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.8% I2 Maximum Allowable Nonvolatile matter . . . . . . . . . . . . . . . . . . . 0.01% Chlorine and bromine (as Cl) . . . . . . . . . . . . . 0.005%
TESTS Assay (By titration of oxidizing power). Weigh accurately about 0.5 g, and transfer to a glass-stoppered conical flask. Add 50 mL of water containing 3 g of potassium iodide and 1 mL of sulfuric acid. Stopper, swirl, and allow to stand for 2–3 min. Titrate the iodine with 0.1 N sodium thiosulfate volumetric solution, adding 3 mL of starch indicator solution near the end of the titration. One milliliter of 0.1 N sodium thiosulfate corresponds to 0.01269 g of I2.
© 2017 American Chemical Society
A
DOI:10.1021/acsreagents.4175 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Nonvolatile Matter Weigh accurately about 10 g, and transfer to a tared, preconditioned porcelain crucible or dish. Heat on a hot plate (~100 °C) until the sample is volatilized. Heat to 105 °C for 1 h, cool in a desiccator, and weigh.
Chlorine and Bromine Add 1.0 g to 100 mL of hot water containing 0.6 g of hydrazine sulfate in a 250 mL Erlenmeyer flask. Heat on a steam bath until dissolution occurs. Cool, and neutralize with 1 N sodium hydroxide volumetric solution, using an external indicator. Add 2 mL of hydrogen peroxide and 1 mL of phosphoric acid. Heat to boiling, and boil gently until 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 for 10 min longer. If no color develops, boil for 10 min. Filter if necessary through a chloride-free filter, dilute with water to 100 mL, and take a 20 mL portion. For the standard, dilute a solution containing 0.01 mg of chloride ion (Cl) with water to 20 mL. Add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution to each. Any turbidity in the solution of the sample should not exceed that in the standard.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4175 ACS Reagent Chemicals, Part 4
