(Ph. Eur. monograph 0031)
I2 253.8 7553-56-2
Action and use
Antiseptic; antithyroid.
Preparations
Alcoholic Iodine Solution
Aqueous Iodine Oral Solution
Povidone-Iodine Eye Drops
Povidone-Iodine Mouthwash
Povidone-Iodine Solution
DEFINITION
Content
99.5 per cent to 100.5 per cent of I.
CHARACTERS
Appearance
Greyish-violet, brittle plates or fine crystals with a metallic sheen.
Solubility
Very slightly soluble in water, very soluble in concentrated solutions of iodides, soluble in ethanol (96 per cent), slightly soluble in glycerol.
It volatilises slowly at room temperature.
IDENTIFICATION
A. Heat a few fragments in a test-tube. Violet vapour is evolved and a bluish-black crystalline sublimate is formed.
B. To a saturated solution add starch solution R. A blue colour is produced. Heat until decolourised. On cooling, the colour reappears.
TESTS
Solution S
Triturate 3.0 g with 20 mL of water R, filter, wash the filter with water R and dilute the filtrate to 30 mL with the same solvent. To the solution add 1 g of zinc powder R. When the solution is decolourised, filter, wash the filter with water R and dilute to 40 mL with the same solvent.
Bromides and chlorides
Maximum 250 ppm.
To 10 mL of solution S add 3 mL of ammonia R and 6 mL of silver nitrate solution R2. Filter, wash the filter with water R and dilute the filtrate to 20 mL with the same solvent. To 10 mL of the solution add 1.5 mL of nitric acid R. After 1 min, any opalescence in the solution is not more intense than that in a standard prepared at the same time by mixing 10.75 mL of water R, 0.25 mL of 0.01 M hydrochloric acid, 0.2 mL of dilute nitric acid R and 0.3 mL of silver nitrate solution R2.
Non-volatile substances
Maximum 0.1 per cent.
Heat 1.00 g in a porcelain dish on a water-bath until the iodine has volatilised. Dry the residue at 100-105 °C. The residue weighs a maximum of 1 mg.
ASSAY
Introduce 0.200 g into a flask containing 1 g of potassium iodide R and 2 mL of water R and add 1 mL of dilute acetic acid R. When dissolution is complete, add 50 mL of water R and titrate with 0.1 M sodium thiosulfate, using starch solution R as indicator.
1 mL of 0.1 M sodium thiosulfate is equivalent to 12.69 mg of I.
