Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Ammonium 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 Ammonium 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, Insoluble Matter, Residue after Ignition, Chloride, Bromide, Phosphate, Sulfate, Barium, Heavy Metals, and Iron.
NH4I
Formula Wt 144.94
CAS No. 12027-06-4
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .
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colorless or white solid; may become pale yellow with storage photochemical reactions when heated, it partly decomposes and partly sublimes 170 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% NH4I
Insoluble matter . . . . . . . . Residue after ignition. . . . . Chloride and bromide (as Cl) Phosphate (PO4) . . . . . . . . Sulfate (SO4) . . . . . . . . . . Barium (Ba) . . . . . . . . . . . Heavy metals (as Pb) . . . . . Iron (Fe) . . . . . . . . . . . . .
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© 2017 American Chemical Society
Maximum Allowable 0.005% 0.05% 0.005% 0.001% 0.05% 0.002% 0.001% 5 ppm
A
DOI:10.1021/acsreagents.4026 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
TESTS Assay (By oxidation–reduction titration of iodide). Weigh to the nearest 0.1 mg about 0.3 g of sample, and dissolve with about 20 mL of water in a 250 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 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 0.014494 g of NH4I.
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20 g dissolved in 200 mL of water.
Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 2.0 g.
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 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 20 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.
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For the Determination of Phosphate, Sulfate, Heavy Metals, and Iron
S a m p l e S o l u t i o n A . Dissolve 20.0 g in 40 mL of water in a 600 mL beaker, and add about 10 mg of sodium carbonate. Add 16 mL of hydrochloric acid and 32 mL of nitric acid, cover with a watch glass, and warm on a hot plate (~100 °C). When the rapid evolution of iodine ceases, add an additional 16 mL of nitric acid and 24 mL of hydrochloric acid. Digest in the covered beaker until the bubbling ceases, remove the watch glass, and evaporate to dryness. B l a n k S o l u t i o n B . Evaporate to dryness the quantities of acids and sodium carbonate used to prepare sample solution A. Dissolve the residues of both solutions in separate 20 mL portions of water, filter if necessary, and dilute each with water to 100 mL (1 mL of sample solution A = 0.2 g).
Phosphate† [Part 2: Colorimetry and Turbidimetry; Phosphate; Procedure for Phosphate, Method 1 (Direct Molybdenum Blue)]. Evaporate 10 mL of sample solution A (2 g sample) to dryness on a hot plate (~100 °C). Dissolve the residue in 25 mL of approximately 0.5 N sulfuric acid. Use 10 mL of blank solution B to prepare the standard solution.
© 2017 American Chemical Society
B
DOI:10.1021/acsreagents.4026 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
†
Sulfate
[Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1]. Use 0.5 mL of sample solution A. Use 0.5 mL of blank solution B to prepare the standard solution.
Barium (by flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Barium
S a m p l e S t o c k S o l u t i o n . Dissolve 50.0 g of sample in about 70 mL of water. Transfer to a 100 mL volumetric flask, at room temperature, dilute to the mark with water, and mix (1 mL = 0.50 g).
For the Determination of Barium
Element
Wavelength (nm)
Sample Wt (g)
Standard Added (mg)
Flame Type*
Background Correction
Ba
553.6
5.0
0.10; 0.20
N/A
No
*N/A is nitrous oxide/acetylene.
Heavy Metals† [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dilute 10 mL of sample solution A (2 g sample) with water to 25 mL. Use 10 mL of blank solution B to prepare the standard solution.
Iron† [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 10 mL of sample solution A (2 g sample). Prepare the standard with 10 mL of blank solution B.
© 2017 American Chemical Society
C
DOI:10.1021/acsreagents.4026 ACS Reagent Chemicals, Part 4
