Monograph pubs.acs.org/doi/book/10.1021/acsreagents
Potassium Bromide 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 Bromide provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), aqueous solubility, and density. 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, Bromate, Iodate, Chloride, Iodide, Sulfate, Barium, Heavy Metals, Iron, Calcium, Magnesium, and Sodium.
KBr
Formula Wt 119.00
CAS No. 7758-02-3
GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . . Density . . . . . . . . . . . . . . . .
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colorless solid analytical standard; redox reagent melting point, 730 °C 65 g in 100 mL at 20 °C 2.75
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . ≥99.0% KBr pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 5.0–8.8
Insoluble matter . Bromate (BrO3) . . Iodate (IO3) . . . . Chloride (Cl) . . . Iodide (I). . . . . . Sulfate (SO4) . . .
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© 2017 American Chemical Society
Maximum Allowable 0.005% 0.001% 0.001% 0.2% 0.001% 0.005%
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DOI:10.1021/acsreagents.4279 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Barium (Ba) . . . . . . . . . . Heavy metals (by ICP–OES) Iron (Fe) . . . . . . . . . . . . Calcium (Ca) . . . . . . . . . Magnesium (Mg) . . . . . . . Sodium (Na) . . . . . . . . . .
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0.002% 5 ppm 5 ppm 0.002% 0.001% 0.02%
TESTS Assay (By argentimetric titration of bromide content). Weigh accurately about 0.5 g of sample, and dissolve in 50 mL of water. Add 50.0 mL of 0.1 N silver nitrate volumetric solution and 10 mL of dilute nitric acid (1:10), and titrate the excess silver nitrate with 0.1 N ammonium thiocyanate volumetric solution, using ferric ammonium sulfate indicator solution. One milliliter of 0.1 N silver nitrate corresponds to 0.0119 g of KBr.
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.
Bromate and 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 0.10 mg of bromate ion (BrO3) and 0.10 mg of iodate ion (IO3).
Chloride Dissolve 0.50 g in 15 mL of dilute nitric acid (1: 2) in a small flask. Add 3 mL of 30% hydrogen peroxide, and digest on a hot plate (~100 °C) until the solution is colorless. Wash down the sides of the flask with a little water, digest for an additional 15 min, cool, and dilute with water to 200 mL. Dilute 2.0 mL to 20 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 reagents used in the test.
Iodide Dissolve 2.5 g in 50 mL of water in a 100 mL volumetric flask. For the control, dissolve 0.5 g in a similar flask, and add 0.02 mg of iodide ion (I). Treat each solution as follows: Add 2 mL of bromine water, mix, and allow to stand for 5 min. Add 2 mL of sodium formate solution (25 g per 100 mL), and mix. Add 1 mL of 1 N sodium hydroxide volumetric solution or enough to
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4279 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
bring the pH to 9 or greater, dilute to volume with water, and mix. Using differential pulse polarography, as described in [Part 2: Direct Electrometric Methods; Specific Polarographic Procedures; Polarographic Procedure for Bromate and Iodate], starting with transfer of the solution to the polarographic cell, determine any iodate present. The wave for the sample, after correction for any iodate originally present, should not exceed that for the control (similarly corrected).
Sulfate [Part 2: Colorimetry and Turbidimetry; Sulfate; Procedure for Sulfate, Method 1].
Barium For the sample, dissolve 6.0 g in 15 mL of water. For the control, dissolve 1.0 g in 15 mL of water and add 0.1 mg of barium. To each solution, add 5 mL of acetic acid, 5 mL of 30% hydrogen peroxide, and 1 mL of hydrochloric acid. Digest in a covered beaker on a hot plate (~100 °C) until reaction ceases, uncover, and evaporate to dryness. Dissolve the residues in 15 mL of water, filter if necessary, and dilute with water to 23 mL. Add 2 mL of 10% potassium dichromate reagent solution, and add ammonium hydroxide until the orange color is just dissipated and the yellow color persists. Add 25 mL of methanol, stir vigorously, and allow to stand for 10 min. The turbidity in the solution of the sample should not exceed that in the control.
Heavy Metals ([Part 2: Trace and Ultratrace Elemental Analysis; Inductively Coupled Plasma−Optical Emission Spectroscopy (ICP–OES); Calculation of Heavy Metals (by ICP–OES) Results], by ICP–OES). Use 2.0 g sample.
Iron [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 2.0 g. In both sample and control solutions, use 4 mL of hydrochloric acid.
Calcium, Magnesium, and Sodium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).
For the Determination of Calcium, Magnesium, and Sodium
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 80 mL of water. Transfer to a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.05 g).
For the Determination of Calcium, Magnesium, and Sodium
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
0.05
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.4279 ACS Reagent Chemicals, Part 4
