Staining Reticulin with Gold

This bromine-iodine-gold chloride-reduction sequence stains reticulin in formalin-fixed paraffin sections without risk of sections becoming detached. After hydration, sections are exposed to 0.2% bromine water containing 0.01% KBr for 1 hr, then rinsed and placed for 5 min in a solution consisting of KI, 2 gm; iodine crystals, 1 gm; and distilled water, 100 ml. After this the sections are well washed in distilled water, immersed for 5 min in 1% w/v aqueous solution of chloro-auric acid, again rinsed in distilled water, and the gold is reduced by placing in freshly made 3% H₂O₂ for 2-4 hr at 37 C, or in 2% oxalic acid for 1-3 hr at the same temperature.