Potassium Iodate

Potassium Iodate BP
KIO3 -- 214.0 -- CAS 7758-05-6

DEFINITION
Potassium Iodate contains not less than 99.0% and not more than 101.0% of KIO3, calculated with reference to the dried substance.

CHARACTERISTICS
A white crystalline powder.
Slowly soluble in water; insoluble in ethanol (96%).
Dissolve 10 g of the substance being examined in sufficient water to produce 200 ml (solution S1).
Add 25 ml of hydrochloric acid to 6 g of the substance being examined, evaporate to dryness and repeat. Heat until iodine is removed. Dissolve the residue in 2.5 ml of a 25% v/v solution of hydrochloric acid and dilute to 50 ml with water (solution S2).

IDENTIFICATION
A. 1 ml of solution S1 yields reaction B characteristic of potassium salts.
B. Dissolve 0.1 g in 5 ml of water. Add 1 ml of silver nitrate solution followed by 1 ml of sulphur dioxide solution. A yellow precipitate is produced immediately.

TESTS
Acidity or alkalinity: pH of solution S1, 5.0 to 8.0.
Clarity and colour of solution: Solution S1 is clear and colourless.
Chloride, chlorate, bromide, bromate: Dilute 5 ml of solution S1 to 15 ml with water, add 20 ml of sulphur dioxide solution and heat on a water bath for 30 minutes. Heat to boiling, cool, add 10 ml of 18M ammonia and 20 ml of silver nitrate solution R2 and dilute to 70 ml with water. Filter, transfer 35 ml of the filtrate to a Nessler cylinder and acidify with 6 ml of nitric acid . After 5 minutes, any opalescence, when viewed vertically, is not greater than that produced by treating 5 ml of a 0.00165% w/v solution of sodium chloride at the same time and in the same manner (0.02%).
Iodide: Add 1 ml of 1.8M sulphuric acid to 25 ml of solution S1 and shake with 1 ml of chloroform. Any violet colour produced is not more intense than that of a solution prepared at the same time and in the same manner but using 5 ml of solution S1 and 2 ml of iodide standard solution (10 ppm I) (20 ppm).
Sulphate: Add 1 ml of a 25% w/v solution of barium chloride to 1.5 ml of sulphate standard solution (10 ppm SO4), shake and allow to stand for 1 minute. Add 12.5 ml of solution S2 diluted to 15 ml with distilled water and 0.5 ml of 5M acetic acid and allow to stand for 5 minutes. Any opalescence produced is not more intense than that of a standard prepared in the same manner but using 7.5 ml of sulphate standard solution (10 ppm SO4) diluted to 15 ml with distilled water in place of the solution being examined (50 ppm).
Heavy metals: Adjust the pH of 20 ml of solution S2 to about 5 with 5M ammonia. The solution complies with limit test A for heavy metals, Appendix VII. Use 10 ml of lead standard solution (2 ppm Pb) to prepare the standard (20 ppm).
Loss on drying: When dried at 130° for 1 hour, loses not more than 0.5% of its weight. Use 1 g.

Potassium Iodide USP
KI -- 166.00
Potassium iodide -- [CAS 7681-11-0]

Potassium Iodide contains not less than 99.0 percent and not more than 101.5 percent of KI, calculated on the dried basis.

Identification: A solution of it meets the requirements of the tests for Potassium and for Iodide.
Alkalinity: Dissolve 1.0 g in 10 mL of water, and add 0.1 mL of 0.1 N sulfuric acid and 1 drop of phenolphthalein TS: no color is produced.
Loss on drying: Dry it at 105C for 4 hours: it loses not more than 1.0% of its weight.
Iodate: Dissolve 1.1 g in sufficient ammonia- and carbon dioxide-free water to obtain 10 mL of solution, and transfer to a color-comparison tube. Add 1 mL of starch TS and 0.25 mL of 1.0 N sulfuric acid, mix, and compare the color with that of a control containing, in a similar volume, 100 mg of Potassium Iodide, 1 mL of standard iodate solution [prepare by diluting 1 mL of potassium iodate solution (1 in 2500) with water to 100 mL], 1 mL of starch TS, and 0.25 mL of 1.0 N sulfuric acid. Any color produced in the solution of the test specimen does not exceed that in the control: not more than 4 µg per g is found.
Limit of nitrate, nitrite, and ammonia: To a solution of 1 g in 5 mL of water contained in a test tube of about 40-mL capacity add 5 mL of 1 N sodium hydroxide and about 200 mg of aluminum wire. Insert a pledget of purified cotton in the upper portion of the test tube, and place a piece of moistened red litmus paper over the mouth of the tube. Heat the test tube and its contents in a steam bath for 15 minutes: no blue coloration of the paper is discernible.
Thiosulfate and barium: Dissolve 0.5 g in 10 mL of ammonia- and carbon dioxide-free water, and add 2 drops of 2 N sulfuric acid: no turbidity develops within 1 minute.
Heavy metals: Dissolve 2.0 g in 25 mL of water: the limit is 0.001%.

Potassium Iodide BP (Ph Eur monograph 0186)
KI -- 166.0 -- 7681-11-0
Content: 99.0 per cent to 100.5 per cent (dried substance).

CHARACTERS
Appearance: White or almost white powder or colourless crystals.
Solubility: Very soluble in water, freely soluble in glycerol, soluble in ethanol (96 per cent).

IDENTIFICATION
A. Solution S (see Tests) gives the reactions of iodides (2.3.1).
B. Solution S gives the reactions of potassium (2.3.1).

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.
Alkalinity: To 12.5 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 is required to change the colour of the indicator.
Iodates: To 10 ml of solution S add 0.25 ml of iodide-free starch solution R and 0.2 ml of dilute sulphuric acid R and allow to stand protected from light for 2 minutes. No blue colour develops.
Sulphates: Maximum 150 ppm.
Dilute 10 ml of solution S to 15 ml with distilled water R.
Thiosulphates: To 10 ml of solution S add 0.1 ml of starch solution R and 0.1 ml of 0.005 M iodine. A blue colour is produced.
Iron: Maximum 20 ppm.
Dilute 5 ml of solution S to 10 ml with water R.
Heavy metals: Maximum 10 ppm.
12 ml of solution S complies with test A. Prepare the reference solution using lead standard solution (1 ppm Pb) R.
Loss on drying: Maximum 1.0 per cent, determined on 1.00 g of previously powdered substance by drying in an oven at 105C for 3 h.