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Lugol’s Iodine

Lugol’s Iodine


Potassium iodide2g
Distilled water100mL


  1. Combine the iodine and potassium iodide, then add 5 mL of the water. The iodine should dissolve in a few seconds.
  2. When it has, add the remaining water and filter.


  • Iodine dissolves very rapidly in strong potassium iodide solutions, but only very slowly in weak ones. Adding all of the water at once causes the iodine to dissolve over about 24-48 hours. Mixing the dry chemicals and adding just a small volume of water causes them to dissolve in a few seconds.
  • The formula given above for Lugol’s iodine is by far the most widely accepted. However, in the 1950 edition of The Microtomist’s Vade Mecum, the authors note that the formula varies considerably. Lillie made similar comments. It would appear that at one time the name may have been used as a generic term for any iodine-potassium iodide solution of any concentration. When used to remove mercury pigment, the differences may not be important, but for applications where the iodine is used as an oxidizing agent, differences in concentration may affect the results obtained. It is suggested that when Lugol’s iodine is specified the formula should be explicitly given, so as to avoid any confusion. Simply referring to it by name is likely to mislead.

Safety Note

Prior to handling any chemical, consult the Safety Data Sheet (SDS) for proper handling and safety precautions.


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    The Microtomist’s Formulary and Guide. p.
    Originally published by: The Blakiston Co.
    Republished by: Robert E. Krieger Publishing Co.
    Lee, (1905)
    Microtomist’s Vade Mecum, ed. 8
    Churchill, London, England
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