Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Sodium 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 Sodium 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, Chloride, Bromide, Iodate, Phosphate, Sulfate, Heavy Metals, Iron, Calcium, Magnesium, Potassium, and Barium.
NaI
Formula Wt 149.89
CAS No. 7681-82-5
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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white solid; may become brown on exposure to air iodometric reagent melting point, 651 °C 200 g in 100 mL
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.5% NaI pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 6.0–9.0 Maximum Allowable Insoluble matter . . . . . . . . . . . . . . . . . . . . . 0.01% 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 Iron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm Calcium (Ca) . . . . . . . . . . . . . . . . . . . . . . . 0.002%
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4352 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Magnesium (Mg) . . . . . . . . . . . . . . . . . . . . . 0.001% Potassium (K) . . . . . . . . . . . . . . . . . . . . . . . 0.01%
TESTS Assay (By titration of iodide content). Weigh accurately about 0.5 g, and dissolve in 20 mL of water in a glass-stoppered conical 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. Shake vigorously for 30 s, and continue the titration, shaking vigorously after each addition, until the iodine color in the chloroform is discharged. One milliliter of 0.05 M potassium iodate corresponds to 0.01499 g of NaI.
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 200 mL of water.
Chloride and Bromide Dissolve 1.0 g in 100 mL of water in a distillation flask. Add 1 mL of 30% 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 with water, 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, 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).
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]. Use 1.0 g. Any yellow iodine color that develops can be discharged by the addition of a few milligrams of ascorbic acid.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4352 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
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)]. Use 2.0 g.
Calcium, Magnesium, Potassium, 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, Potassium, and Barium
S a m p l e S t o c k S o l u t i o n . Dissolve 50.0 g sample in about 70 mL of water. Transfer to a 100 mL volumetric flask, at room temperature, and dilute to t h e m a r k with water (1 mL = 0.50 g).
For the Determination of Calcium, Magnesium, Potassium, and Barium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ca
422.7
1.00
0.02; 0.04
N/A
No
Mg
285.2
1.00
0.01; 0.02
A/A
Yes
Ba
553.6
5.0
0.10; 0.20
N/A
No
K
766.5
0.20
0.01; 0.02
A/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.4352 ACS Reagent Chemicals, Part 4
