Moisten 5 grams of the substance in a platinum dish with 20 cc. of a
5-percent solution of sodium carbonate, evaporate to dryness and ignite
as thoroughly as possible at a temperature not exceeding dull redness.
Extract with hot water, filter and wash. Return the residue to the
platinum dish and ignite to an ash; dissolve in nitric acid, and add
this solution to the water extract. Add a known volume of N/10 silver
nitrate in slight excess to the combined solutions. Stir well, filter
and wash the silver chloride precipitate thoroughly. To the filtrate and
washings add 5 cc. of a saturated solution of ferric alum and a few cc.
of nitric acid. Titrate the excess silver with N/10 ammonium or
potassium thiocyanate until a permanent light brown color appears.
Calculate the amount of chlorin.