(a) Quassin is the bitter principle of quassia wood (occurring as a mixture of two isomeric forms). It shall be a good commercial grade of purified amorphous quassin, standardized as to bitterness.

(b) Bitterness. An aqueous solution of quassin shall be distinctly bitter at a 1 to 250,000 dilution. To test: Dissolve 0.1 gram of quassin in 100 mL of 95 percent alcohol, then dilute 4 mL of the solution to 1,000 mL with distilled water, mix well and taste.

(c) Identification test. Dissolve about 0.5 gram of quassin in 10 mL of 95 percent alcohol and filter. To 5 mL of the filtrate, add 5 mL of concentrated hydrochloric acid and 1 mg of phloroglucinol and mix well. A red color develops.

(d) Optical assay. When 1 gram of quassin (in solution in a small amount of 95 percent alcohol) is dissolved in 10,000 mL of water, the absorbance of the solution in a 1 cm cell at a wavelength of 258 millimicrons shall not be less than 0.400.

(e) Solubility. When 0.5 gram of quassin is added to 25 mL of 190 proof alcohol, it shall dissolve completely.