Removal of mercury pigment involves which sequence?

• A. Iodine followed by Sodium Thiosulfate
• B. Sodium thiosulfate followed by Iodine
• C. Alcoholic picric acid then alkaline alcohol
• D. Water only

Answer: (A)

The sequence relies on oxidizing the mercury pigment first and then clearing it with a thiosulfate step. Iodine serves as the oxidizing agent, converting the pigment into a form that is more soluble and easier to remove from the tissue. After this oxidation, sodium thiosulfate is used to dissolve and wash away the pigment remnants, and it also helps neutralize any residual iodine. Doing the thiosulfate step first wouldn’t allow the pigment to be converted into the soluble form, so removal would be incomplete, and the tissue could retain the pigment. The other options don’t provide the proper chemical transformation needed for mercury pigment removal, and water alone isn’t reactive enough to clear it.