Strong Iodine Solution
»Strong Iodine Solution contains,in each 100mL,not less than 4.5g and not more than 5.5g of iodine (I),and not less than 9.5g and not more than 10.5g of potassium iodide (KI).
Strong Iodine Solution may be prepared by dissolving 50g of Iodine and 100g of Potassium Iodide in 100mLof Purified Water,then adding Purified Water to make the product measure 1000mL.
Packaging and storage—
Preserve in tight containers,preferably at a temperature not exceeding 35
.
.
Identification—
A:
Dilute 1drop with 10mLof water,and add 1mLof starch TS:a deep blue color is produced.
B:
Evaporate a few mLon a steam bath to dryness,and ignite gently to volatilize any free iodine:the residue responds to the tests for Potassium á191ñand for Iodide á191ñ.
Assay for iodine—
Transfer 10.0mLof Solution into a glass-stoppered,500-mLflask,add 10mLof water,and titrate with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Each mLof 0.1Nsodium thiosulfate is equivalent to 12.69mg of I.
Assay for potassium iodide—
Transfer 10.0mLof Solution to a glass-stoppered,500-mLflask,add 30mLof water and 50mLof hydrochloric acid,cool to room temperature,and titrate with 0.05Mpotassium iodate VSuntil the dark brown solution that is produced becomes pale brown.Add 1mLof amaranth TS,and continue the titration slowly until the red color just changes to yellow.The difference between the number of mLof 0.05Mpotassium iodate used and half the number of mLof 0.1Nsodium thiosulfate used in the Assay for iodine,multiplied by 16.60,represents the number of mg of KIin the volume of the Solution taken.
Auxiliary Information—
Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 1030
Phone Number:1-301-816-8394