Lugol's Iodine


Ingredient var I
Iodine 1 g
Potassium iodide 2 g
Distilled water 100 mL


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

There are several variations of iodine solutions. Other formulae are:–

Author I KI Water Note
Gray 6 4 100 Quotes Lee, but perhaps an error. See next
Lee, Cowdry 4 6 100 Bolles-Lee (1950).
Romeis 1 2 300 Bolles-Lee (1950). Usually called Gram’s iodine now.
Langeron 1 2 200 Bolles-Lee (1950).
Clark & Dodds 2 4 100  
Mayer 0.5 5 5 Bolles-Lee (1950). Dilutes with 95 mL 90% ethanol.
Humason 1 2 12 3 formulae given - 12, 100 and 300 mL water.


  1. 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.
  2. 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 oxidising agent, differences in concentration may affect the results obtained. It is suggested that when Lugol’s iodine is specified the formula should be explicitely given, so as to avoid any confusion. Simply referring to it by name is likely to mislead.



Culling C.F.A., (1974)
Handbook of histopathological and histochemical techniques Ed. 3
Butterworth, London, UK.

Clark, G. and Dodds, H. M., (1983)
Lugol’s hematoxylin
Stain Technology, v. 58, p.232.

Gray, Peter. (1954)
The Microtomist's Formulary and Guide.
Originally published by:– The Blakiston Co.
Republished by:– Robert E. Krieger Publishing Co.
    Lee, (1905)
    Microtomist’s Vade Mecum, ed. 8
    Churchill, London, England

Bolles Lee, A.. Edited by Gatenby, J.B. and Beams, H.W., (1950)
The Microtomist's Vade-Mecum. 11 ed.,
Churchill, London, UK.

Humason, G. L., (1967)
Animal tissue techniques, Ed. 2
W. H. Freeman and Company, San Francisco, Ca, USA

Cowdry, E. V., (1943)
Microscopic technique in biology and medicine
Williams and Wilkins Company, Baltimore, Md, USA

Lillie, R.D., (1954)
Histopathologic technique and practical histochemistry Ed.2
Blakiston, New York, USA.



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