Staining, Histochemistry and Histotechnology
(Frequently Asked Questions)
Dr. John A. Kiernan
Department of Anatomy
and Cell Biology
The University of Western Ontario
Iodine for removing mercury deposits
[It is necessary to remove mercury deposits from specimens fixed in B5 or other fixatives that contain mercuric
chloride. Textbooks recommend either including a solution of iodine
(0.5 to 1%) in 70% alcohol in the series of solvents for dehydrating before embedding, or treating the sections after hydration with iodine followed by sodium thiosulfate. ]
I am interested in the possibility adding of iodine to the first xylene, in a staining machine. What is the percentage or recipe
for that solution, and will it corrode metal parts?
We use a 0.5% solution of iodine in xylene for 5 minutes. We have been doing this regularly for about 6 months and have only had a problem with a couple of lymph nodes, in that the mercuric crystals were not completely removed. We had to give additional
treatment off the machine.
We have a Leica stainer, and everything inside looks like stainless steel. It seems to be unaffected by the iodine thus
far. We do always use the same staining dish and lid for the iodine/xylene because the plastic is stained.
At my previous lab we used 1 percent iodine in the first xylene to clear out the mercury crystals. That was using glass jars and
metal racks in a manual method. There were no problems with corrosion of the racks.