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Name: Basanta
Status: educator
Grade: N/A
Location: KY
Date: March 2008


Question:
Why is iodine solution prepared with potassium iodide?



Replies:
It is not always necessary to do that. Iodine (I2) has limited solubility in water; however it is quite soluble in many organic solvents. When for other reasons it is desired to have the iodine in aqueous solution, adding potassium iodide form the triiodide complex (I3)[-1], which is quite soluble in water. For some applications a cosolvent such as isopropyl alcohol is more desirable. In other applications, the polymer, polyvinyl pyrrolidone (PVP), which also forms a stable complex with I2. This combination is sold in pharmacies under the trade name "Providone". Both the isopropyl alcohol formulation and the (PVP) formulation will allow solutions containing up to about 10% iodine.

Vince Calder



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