Packaging and storage—
Preserve in tight containers.
Labeling—
Label it to indicate the viscosity in solutions of stated concentrations of either 1% (w/w) or 2% (w/w).
Identification—
Add about 1 g of powdered Carboxymethylcellulose Sodium 12 to 50 mL of water, while stirring to produce a uniform dispersion. Continue the stirring until a clear solution is produced, and use the solution for the following tests.
A:
To 1 mL of the solution, diluted with an equal volume of water, in a small test tube, add 5 drops of 1-naphthol TS. Incline the test tube, and carefully introduce down the side of the tube 2 mL of sulfuric acid so that it forms a lower layer: a red-purple color develops at the interface.
B:
To 5 mL of the solution add an equal volume of
barium chloride TS: a fine, white precipitate is formed.
C:
A portion of the solution responds to the tests for
Sodium 
191
.
Viscosity 911—
Determine the viscosity in a water solution at the concentration stated on the label. Using undried Carboxymethylcellulose Sodium 12, weigh accurately the amount which, on the dried basis, will provide 200 g of solution of the stated concentration. Add the substance in small amounts to about 180 mL of stirred water contained in a tared, wide-mouth bottle, continue stirring rapidly until the powder is well wetted, add sufficient water to make the mixture weigh 200 g, and allow to stand, with occasional stirring, until solution is complete. Adjust the temperature to 25 ± 0.2
, and determine the viscosity, using a rotational type of viscosimeter, making certain that the system reaches equilibrium before taking the final reading. The viscosity of solutions of 2% concentration is not less than 80.0% and not more than 120.0% of that stated on the label; the viscosity of solutions of 1% concentration is not less than 75.0% and not more than 140.0% of that stated on the label.
pH 791:
between 6.5 and 8.5, in a solution (1 in 100).
Loss on drying 731—
Dry it at 105
for 3 hours: it loses not more than 10.0% of its weight.
Heavy metals—
Determine as directed in the test for
Heavy metals under
Methylcellulose, using a 1.0-g specimen: the limit is 20 µg per g.
Sodium chloride and Sodium glycolate—
SODIUM CHLORIDE—
Weigh accurately about 5 g of it into a 250-mL beaker, add 50 mL of water and 5 mL of 30 percent hydrogen peroxide, and heat on a steam bath for 20 minutes, stirring occasionally to ensure hydration. Cool, add 100 mL of water and 10 mL of nitric acid, and titrate with 0.05 N silver nitrate VS, determining the endpoint potentiometrically, using a silver electrode and a mercurous sulfate electrode having a potassium sulfate bridge, and stirring constantly. Calculate the percentage of sodium chloride in the specimen taken by the formula,
584.4
VN/[(100
b)
W],
in which
V and
N represent the volume, in mL, and the normality, respectively, of the silver nitrate,
b is the percentage of
Loss on drying, determined separately;
W is the weight, in g, of the specimen; and 584.4 is an equivalence factor for sodium chloride.
SODIUM GLYCOLATE—
Transfer about 500 mg of it, accurately weighed, into a 100-mL beaker, moisten thoroughly with 5 mL of glacial acetic acid, followed by 5 mL of water, and stir with a glass rod to ensure proper hydration (usually about 15 minutes). Slowly add 50 mL of acetone, with stirring, then add 1 g of sodium chloride, and stir for several minutes to ensure complete precipitation of the carboxymethylcellulose. Filter through a soft, open-textured paper, previously wetted with a small amount of acetone, and collect the filtrate in a 100-mL volumetric flask. Use an additional 30 mL of acetone to facilitate the transfer of the solids and to wash the filter cake, then dilute with acetone to volume, and mix.
Prepare a series of standard solutions as follows. Transfer 100 mg of glycolic acid, previously dried in a desiccator at room temperature overnight and accurately weighed, to a 100-mL volumetric flask, dissolve in water, dilute with water to volume, and mix. Use this solution within 30 days. Transfer 1.0 mL, 2.0 mL, 3.0 mL, and 4.0 mL portions of the solution, respectively, to separate 100-mL volumetric flasks, add water to each flask to make 5 mL, then add 5 mL of glacial acetic acid, dilute with acetone to volume, and mix.
Transfer 2.0 mL of the test solution and 2.0 mL of each standard solution to separate 25-mL volumetric flasks, and prepare a blank flask containing 2.0 mL of a solution containing 5% each of glacial acetic acid and water in acetone. Place the uncovered flasks in a boiling water bath for 20 minutes, accurately timed, to remove the acetone, remove from the bath, and cool. Add to each flask 5.0 mL of
2,7-dihydroxynaphthalene TS, mix, add an additional 15 mL, and again mix. Cover the mouth of each flask with a small piece of aluminum foil. Place the flasks upright in a boiling water bath for 20 minutes, then remove from the bath, cool, dilute with sulfuric acid to volume, and mix.
Determine the absorbance of each solution at 540 nm, with a suitable spectrophotometer, against the blank, and prepare a standard curve using the absorbances obtained from the standard solutions. From the standard curve and the absorbance of the test specimen, determine the weight (w), in mg, of glycolic acid in the specimen, and calculate the percentage of sodium glycolate in the specimen taken by the formula,
12.9
w/[(100
b)
W],
in which 12.9 is a factor converting glycolic acid to sodium glycolate; b is the percentage of Loss on drying, determined separately; and W is the weight, in g, of the specimen. The sum of the percentages of sodium chloride and sodium glycolate is not more than 0.5%.
Degree of substitution—
Weigh accurately about 200 mg of Carboxymethylcellulose Sodium 12, previously dried at 105
for 3 hours, and transfer to a glass-stoppered, 250-mL conical flask. Add 75 mL of glacial acetic acid, connect the flask to a water-cooled condenser, and reflux gently on a hot plate for 2 hours. Cool, transfer the solution to a 250-mL beaker with the aid of 50 mL of glacial acetic acid, and titrate with 0.1 N perchloric acid in dioxane VS while stirring with a magnetic stirrer. Determine the endpoint potentiometrically with a pH meter equipped with a standard glass electrode and a calomel electrode modified as follows. Discard the aqueous potassium chloride solution contained in the electrode, rinse and fill with the supernatant obtained by shaking thoroughly 2 g each of potassium chloride and silver chloride (or silver oxide) with 100 mL of methanol, then add a few crystals of potassium chloride and silver chloride (or silver oxide) to the electrode.
Record the amount, in mL, of 0.1 N perchloric acid versus mV (0- to 700-mV range), and continue the titration to a few mL beyond the endpoint. Plot the titration curve, and read the volume of 0.1 N perchloric acid at the inflection point. Calculate the degree of substitution in the Carboxymethylcellulose Sodium 12 taken by the formula:
16.2
V/(
G 8.0
V),
in which 16.2 is one-tenth of the molecular weight of 1 anhydroglucose unit; V is the volume, in mL, of 0.1 N perchloric acid; G is the weight, in mg, of Carboxymethylcellulose Sodium 12 taken; and 8.0 is one-tenth of the net increase in molecular mass of 1 anhydroglucose unit for each sodium carboxymethyl group added.
