Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Iodide 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 Iodide 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, pH of a 5% Solution at 25.0 °C, Insoluble Matter, Loss on Drying, Chloride, Bromide, Iodate, Phosphate, Sulfate, Heavy Metals, Iron, Calcium, Magnesium, Sodium, and Barium.
KI
Formula Wt 166.00
CAS No. 7681-11-0
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . colorless or white solid; may become yellow when exposed to light and humidity Applications . . . . . . . . . . . . . . . . . . . . . . . . iodometric titrations; reducing agent Change in state (approximate) . . . . . . . . . . . . melting point, 680 °C Aqueous solubility . . . . . . . . . . . . . . . . . . . . 145 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% KI pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 6.0–9.2 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.005% Loss on drying . . . . . . . . . . . . . . . . . . . . . . 0.2% Chloride and bromide (as Cl) . . . . . . . . . . . . . 0.01% Iodate (IO3) . . . . . . . . . . . . . . . . . . . . . . . . 3 ppm Phosphate (PO4) . . . . . . . . . . . . . . . . . . . . . 0.001% Sulfate (SO4) . . . . . . . . . . . . . . . . . . . . . . . 0.005% Barium (Ba) . . . . . . . . . . . . . . . . . . . . . . . . 0.002% Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . 5 ppm
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4295 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Iron (Fe) . . . . . Calcium (Ca) . . Magnesium (Mg) Sodium (Na) . . .
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3 ppm 0.002% 0.001% 0.005%
TESTS Assay (By titration of reductive power). Weigh, to the nearest 0.1 mg, about 0.5 g of sample, and dissolve with 20 mL of water in a 200 mL glass-stoppered titration flask. Add 30 mL of hydrochloric acid and 5 mL of chloroform, cool if necessary, and titrate with 0.05 M potassium iodate volumetric solution until the iodine color disappears from the aqueous layer. Stopper, shake vigorously for 30 s, and continue the titration, shaking vigorously after each addition of the iodate, until the iodine color in the chloroform is discharged. One milliliter of 0.05 M potassium iodate corresponds to 0.0166 g of KI.
pH of a 5% Solution at 25.0 °C [Part 2: Direct Electrometric Methods; pH Potentiometry; pH Range; Procedure for pH of a 5% Solution at 25.0 °C].
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 150 mL of water.
Loss on Drying Weigh accurately about 2.0 g of sample in which the large crystals have been crushed, but not ground, with a mortar and pestle. Dry in a tared, preconditioned dish for 6 h at 150 °C.
Chloride and Bromide Dissolve 1.0 g in 100 mL of water in a distilling flask. Add 1 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 30% 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, filter if necessary through a chloride-free filter, and dilute with water to 100 mL. Dilute 10 mL with water to 23 mL, and add 1 mL of nitric acid and 1 mL of silver nitrate reagent solution. Any turbidity should not exceed that produced by 0.01 mg of chloride ion (Cl) in an equal volume of solution containing the quantities of nitric acid and silver nitrate used in the test.
Iodate [Part 2: Direct Electrometric Methods; Specific Polarographic Procedures; Polarographic Procedure for Bromate and Iodate]. Use 10.0 g of sample in 25 mL of solution. For the standard, add 0.03 mg of iodate ion (IO3).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4295 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Phosphate [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Dissolve 2.0 g in water, and add 10 mL of nitric acid and 5 mL of hydrochloric acid. Evaporate to dryness on a hot plate (~100 °C). Dissolve the residue in 25 mL of approximately 0.5 N sulfuric acid and continue as described. For the standard, include the residue from evaporation of the quantities of acids used with the sample.
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Allow 30 min for turbidity to form.
Heavy Metals [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dissolve 6.0 g in water, and dilute with water to 30 mL. Use 25 mL to prepare the sample solution, and use the remaining 5.0 mL to prepare the control solution.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 2 (Hydroxylamine and 1,10-Phenanthroline)]. Dissolve 3.3 g in 50 mL of water, and add 0.1 mL of ammonium hydroxide.
Calcium, Magnesium, Sodium, and Barium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Calcium, Magnesium, Sodium, and Barium
S a m p l e S t o c k S o l u t i o n . Dissolve 5.0 g of sample in water in a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.05 g).
For the Determination of Calcium, Magnesium, Sodium, and Barium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
1.0
0.02; 0.04
N/A
No
Mg
285.2
1.0
0.01; 0.02
A/A
Yes
Na
589.0
0.20
0.005; 0.01
A/A
No
Ba
553.6
5.0
0.10; 0.20
N/A
No
*A/A is air/acetylene; N/A is nitrous oxide/acetylene.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4295 ACS Reagent Chemicals, Part 4
