Packaging and storage—
Preserve in tight containers.
Identification, Infrared Absorption 
197K
—
Do not dry specimens.
Viscosity 911—
Dissolve 15 g, calculated on the anhydrous basis, in 85 g of a mixture of 249 parts of anhydrous acetone and 1 part of water, by weight: the apparent viscosity (see
Procedure for Methylcellulose under
Viscosity 911) is between 45 and 90 centipoises, determined at 25 ± 0.2
.
Water, Method I 921:
not more than 5.0%, a mixture of dehydrated alcohol and methylene chloride (3:2) being used instead of methanol as the solvent.
Limit of free acid—
Transfer 3.0 g, accurately weighed, to a glass-stoppered flask, add 100 mL of dilute methanol (1 in 2), insert the stopper in the flask, and shake for 2 hours. Filter, and wash the flask and the filter with two 10-mL portions of the methanol solution, adding the washings to the filtrate. Titrate the combined filtrate and washings with 0.1 N sodium hydroxide VS to a phenolphthalein endpoint. Perform a blank determination on 120 mL of the dilute methanol (1 in 2). Calculate the percentage of free acid,
B, by the formula:
0.8306A/W,
in which
A is the volume, in mL, of 0.1 N sodium hydroxide consumed, corrected for the blank; and
W is the weight, in g, of the Cellacefate, calculated on the anhydrous basis. Not more than 3.0%, calculated as phthalic acid, is found.
Phthalyl content—
Transfer about 1 g, accurately weighed, to a conical flask, dissolve in 50 mL of a mixture of alcohol and acetone (3:2), add
phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS. Perform a blank determination, and make any necessary correction. Calculate the percentage of phthalyl, on the acid-free basis, by the formula:
100[(1.491A/W) – 1.795B]/(100 – B),
in which
A is the volume, in mL, of 0.1 N sodium hydroxide consumed after correction for the blank;
W is the weight, in g, of Cellacefate taken, calculated on the anhydrous basis; and
B is the percentage of acid found in the test for
Limit of free acid.
Content of acetyl—
Transfer about 100 mg, accurately weighed, to a glass-stoppered flask, and add 25.0 mL of 0.1 N sodium hydroxide VS. Connect the flask to a reflux condenser, and reflux for 30 minutes. Cool, add 5 drops of phenolphthalein TS, and titrate with 0.1 N hydrochloric acid VS. Perform a blank determination. Calculate the free and combined acids, as acetyl, taken by the formula:
0.4305(A/W),
in which
A is the volume, in mL, of 0.1 N sodium hydroxide consumed after correction for the blank; and
W is the weight, in g, of Cellacefate taken, on the anhydrous basis. Calculate the percentage of acetyl, on the acid-free basis, taken by the formula:
[100(P – 0.5182B)/(100 – B)] – 0.5772C,
in which
P is the free and combined acids, as acetyl;
B is the percentage of acid found in the test for
Limit of free acid; and
C is the percentage of phthalyl found in the test for
Phthalyl content.
