Packaging and storage—
Preserve in tight containers.
Identification—
A:
Shake about 20 mg with 2 mL of water and cautiously add 1 mL of a solution of anthrone in sulfuric acid (350 µg per mL): a blue to greenish blue color develops at the zone of contact.
B:
Shake thoroughly 0.1 g with 10 mL of water. Add 1 g of sodium hydroxide, and shake until it becomes homogeneous. Save 5 mL of this solution for
Identification test
C. To 0.1 mL of this solution add 9 mL of 32 N sulfuric acid, and shake. Heat in a water bath for 3 minutes, accurately timed, and immediately cool in an ice bath. While the mixture is cold, carefully add 0.6 mL of ninhydrin TS, and mix. Allow to stand at room temperature: the red color that appears immediately turns to violet within 100 minutes.
C:
Shake 5 mL of the solution prepared for
Identification test
B with 10 mL of a mixture of acetone and methanol (4:1): a white, flocculent precipitate is formed.
Chloride 
221
—
Shake thoroughly 0.50 g with 30 mL of boiling water, heat on a water bath for 10 minutes, and filter the supernatant by decantation while hot. Wash the residue thoroughly with 50 mL of boiling water, combine the washings with the filtrate, and add water to make 100 mL after cooling: a 10-mL portion of this solution shows no more chloride than is contained in 0.25 mL of 0.02 N hydrochloric acid (0.36%).
Assay—
Proceed as directed for the determination of hydroxypropoxy in the Assay under Hypromellose 2906, except to substitute Low-Substituted Hydroxypropyl Cellulose for Hypromellose 2906 throughout. [NOTE—Since methoxy is not determined, the addition of methyl iodide is not needed.]
for 1 hour, it contains not less than 5.0 percent and not more than 16.0 percent of hydroxypropoxy groups (
OCH2CHOHCH3).