Specifications of Commercial Pure Potassium Bromid

Assay: 99.0% KBr
pH of a 5% solution: 4.5.0-9 at 25C
Insoluble matter: 0.05%
Loss on drying: 0.5% max
Chloride: 0.5% max

Potassium Bromide BP

DEFINITION
Content
98.0 per cent to 100.5 per cent (dried substance).

CHARACTERS
Appearance
White or almost white, crystalline powder or colourless crystals.
Solubility
Freely soluble in water and in glycerol, slightly soluble in alcohol.

IDENTIFICATION
A. It gives reaction of bromides.
B. Solution S (see Tests) gives the reactions of potassium.

TESTS
Solution S
Dissolve 10.0 g in carbon dioxide-free water R prepared from distilled water R and dilute to 100 ml with the same solvent.
Appearance of solution
Solution S is clear and colourless.
Acidity or alkalinity
To 10 ml of solution S add 0.1 ml of bromothymol blue solution R1. Not more than 0.5 ml of 0.01 M hydrochloric acid or 0.01 M sodium hydroxide is required to change the colour of the indicator.
Bromates
To 10 ml of solution S add 1 ml of starch solution R, 0.1 ml of a 100 g/l solution of potassium iodide and 0.25 ml of 0.5 M sulphuric acid and allow to stand protected from light for 5 min. No blue or violet colour develops.
Chlorides
Maximum 0.6 per cent.
Iodides
To 5 ml of solution S add 0.15 ml of ferric chloride solution and 2 ml of methylene chloride.
Shake and allow to separate. The lower layer is colourless.
Sulphates
Maximum 100 ppm.
Iron
Maximum 20 ppm.
Magnesium and alkaline-earth metals
Maximum 200 ppm, calculated as Ca.
Heavy metals
Maximum 10 ppm.
Loss on drying
Maximum 1.0 per cent, determined on 1.000 g by drying in an oven at 105C for 3h.

Potassium Bromide USP

KBr 119.0

Potassium Bromide contains not less than 98.0 percent and not more than 100.5 percent of KBr, calculated on the dried basis. It contains no added substances.

Appearance of solution: clear and colorless.
Test solution— Dissolve 10.0 g in carbon dioxide-free water, and dilute with the same solvent to 100 mL.
Identification—
A: A solution containing 4.5 mg of potassium bromide responds to the test for Bromide.
B: Responds to the test for Potassium.
Acidity or alkalinity— To 10 mL of the solution prepared for the test for Appearance of solution, add 0.1 mL of bromothymol blue TS: not more than 0.5 mL of 0.01 N hydrochloric acid or 0.01 N sodium hydroxide is required to change the color of this solution.
Loss on drying— Dry it at 100 to 105 for 3 hours: it loses not more than 1.0% of its weight.
Bromates—
Starch–mercuric iodide solution— Triturate 1.0 g of soluble starch with 5 mL of water and pour the mixture into 100 mL of boiling water, containing 10 mg of mercuric iodide.
Procedure— To 10 mL of the solution prepared for the test for Appearance of solution add 1 mL of Starch–mercuric iodide solution, 0.1 mL of a 100 g per L solution of potassium iodide, and 0.25 mL of 0.5 M sulfuric acid. Allow to stand protected from light for 5 minutes: no blue or violet color develops.
Limit of chlorine: not more than 0.6%.
Iodides— To 5 mL of the solution prepared for the test for Appearance of solution add 0.15 mL of a 10.5 g per 100 mL ferric chloride solution, and 2 mL of dichloromethane. Shake, and allow to separate. The lower layer is colorless.
Sulfates— A 2.0-g portion shows no more sulfate than corresponds to 0.2 mL of 0.020 N sulfuric acid (0.01%).
Limit of iron: not more than 20 ppm.
Magnesium and alkaline-earth metals— (0.02%, calculated as Ca).
Heavy metals: not more than 10 ppm.