techniques for argentaffin cells: a method using a methenamine-silver solution in combination with gold chloride, sodium thiosulfate, and safranin O; argentaffin granules appear brown-black against a green background; urates: warm sections are treated directly with a hot methenamine-silver solution to produce a blackening of urates; fungi: see Grocott-Gomori methenamine-silver stain; melanin, which reduces silver nitrate. SYN: GMS stain.