Catechu. - Teas are sometimes treated with this substance to increase their astringency and indicate a greater strength than they naturally possess.1 Hager's method for the detection of catechu gave very satisfactory results in the Department's investigations. Small quantities of the substance can not be detected with certainty. The following is a general description of Hager's method:

Boil an extract of tea (1 gram per 100 cc. water) with an excess of litharge; filter; the filtrate should be clear. To a portion of the filtrate add a solution of nitrate of silver. In the presence of catechu a yellow flocculent precipitate is formed, which rapidly becomes dark. Under the same conditions pure tea gives a slight grayish percipitate of metallic silver. The writer prefers a modification of this test, using ferric chloride instead of the silver. Rinse a small porcelain dish with a dilute solution of ferric chloride; a sufficient quantity of the reagent will adhere to the dish. Add the suspected solution, prepared according to Hager. If catechu is present a characteristic green precipitate is formed.