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Yeast Extract
—A water-soluble, peptone-like derivative of yeast cells (Saccharomyces) prepared under optimum conditions, clarified, and dried to a reddish-yellow to brown powder, having a characteristic but not putrescent odor. Soluble in water, forming a yellow to brown solution, having a slightly acid reaction. Contains no added carbohydrate. One g represents not less than 7.5 g of yeast.
Loss on drying 731 Dry it at 105 to constant weight: it loses not more than 5% of its weight.
Residue on ignition— Ignite 500 mg with 1 mL of sulfuric acid: the residue weighs not more than 75 mg (15%).
Coagulable protein— Heat a filtered solution (1 in 20) to boiling: no precipitate is formed.
Chloride (Reagent test)— It shows not more than 5% of Cl, calculated as sodium chloride.
Nitrogen content (Reagent test)— Determine by the Kjeldahl method, using a test specimen previously dried at 105 to constant weight: between 7.2% and 9.5% of N is found.
Microbial content— It meets the requirements of the test for Microbial content under Pancreatic Digest of Casein.

Yellow Mercuric Oxide
—See Mercuric Oxide, Yellow.