XVI. IODINE. For the demonstration of iodine in tissues the following method has been advised by Justus. The experience of other workers with it has not been satisfactory.
1. Harden in absolute alcohol; imbed in celloidin; cut.
2. Soak in water to remove alcohol.
3. Put section in wide-mouthed, stoppered bottle in freshly prepared green chlorine-water for 1-2 minutes.
4. Transfer section on a glass needle to a vessel containing 500 cc. water and 1 cc. of a 1 per cent solution of silver nitrate for 2-3 hours. The section is colored yellow-green, and a precipitate of silver chloride appears.
5. Transfer section to a warm saturated solution of sodium chloride until it becomes light.
6. Wash in distilled water.
7. Transfer to a concentrated solution of mercuric chloride.
8. Examine in pure glycerin.
Iodine should be red.