Packaging and storage—
Preserve in well-closed containers.
Labeling—
Label it to indicate its nominal viscosity in millipascal seconds for a 5 percent m/m solution.
Identification, Infrared Absorption 
197K
.
Viscosity 911—
Shake a quantity of ethylcellulose equivalent to 5.00 g of the dried substance with 95 g of a mixture of 20 g of alcohol and 80 g of toluene until the substance is dissolved. Determine the viscosity using a capillary viscosimeter. The viscosity, determined at 25
and expressed in mPa·s, is not less than 80.0% and not more than 120.0% of that stated on the label for a nominal viscosity greater than 6 mPa·s; and not less than 75.0% and not more than 140.0% of that stated on the label for a nominal viscosity not greater than 6 mPa·s.
Acidity or alkalinity—
To 0.5 g of ethylcellulose, accurately weighed, add 25 mL of carbon dioxide-free water and shake for 15 minutes. Pass through a sintered-glass filter with a maximum diameter of pores between 16 µm and 40 µm. To 10 mL of this solution, add 0.1 mL of
Phenolphthalein solution and 0.5 mL of 0.01 N sodium hydroxide. The solution is pink. To 10 mL of this solution, add 0.1 mL of
Methyl red solution and 0.5 mL of 0.01 N hydrochloric acid. The solution is red.
Phenolphthalein solution—
Dissolve 100 mg of phenolphthalein in 80 mL of alcohol, and dilute with water to 100 mL.
Methyl red solution—
Dissolve 50 mg of methyl red in a mixture of 1.86 mL of 0.1 N sodium hydroxide and 50 mL of alcohol, and dilute with water to 100 mL.
Acetaldehyde—
Introduce 3.0 g into a 250-mL conical flask with a ground-glass stopper, add 10 mL of water, and stir by mechanical means for 1 hour. Allow to stand for 24 hours, filter, and dilute the filtrate with water to 100.0 mL. Transfer 5.0 mL to a 25 mL volumetric flask, add 5 mL of a 0.5 g per L solution of methylbenzothiazolone hydrazone hydrochloride, and heat in a water bath at 60
for 5 minutes. Add 2 mL of
Ferric chloride–sulfamic acid reagent, and heat again at 60
for 5 minutes. Cool, and dilute with water to 25.0 mL. The solution is not more intensely colored than a standard prepared at the same time and in the same manner using, instead of the 5.0 mL of the filtrate, 5.0 mL of a reference solution prepared by diluting 3.0 mL of
Acetaldehyde standard solution with water (100 ppm) to 100.0 mL.
Ferric chloride–sulfamic acid reagent—
Prepare a solution containing 10 g per L of ferric chloride and 10 g per L of sulfamic acid.
Acetaldehyde standard solution—
Dissolve 1.0 g of acetaldehyde in 2-propanol, and dilute with the same solvent to 100.0 mL. Dilute 5.0 mL of the solution with water to 500.0 mL. Prepare immediately before use.
Chlorides—
Disperse 250 mg in 50 mL of water, heat to boiling, and allow to cool, shaking occasionally. Filter, and discard the first 10 mL of the filtrate. Dilute 10 mL of the filtrate with water to 15 mL. Add 1 mL of
Dilute nitric acid, and pour the mixture as a single addition into a test tube containing 1 mL of 0.1 N silver nitrate VS. Prepare a standard in the same manner using 10 mL of
Chloride standard solution and 5 mL of water. Examine the tubes laterally against a black background. After standing for 5 minutes protected from light, any opalescence in the test solution is not more intense than that in the standard (0.1%).
Dilute nitric acid—
Dilute 20 mL of nitric acid with water to 100 mL.
Chloride standard solution—
Immediately before use, dilute with water to 100 times its volume a solution containing sodium chloride equivalent to 0.824 g per L of sodium chloride.
Assay—
NOTE—Hydriodic acid and its reaction byproducts are highly toxic. Perform all steps of the Test solution preparation and the Reference solution preparation in a properly functioning hood.
Internal standard solution—
Dilute 120 µL of toluene with o-xylene to 10 mL.
Test solution—
Transfer 50.0 mg of ethylcellulose, 50 mg of adipic acid, and 2.0 mL of the
Internal standard solution into a suitable 5 mL thick-walled reaction vial with a pressure-tight septum closure. Cautiously add 2.0 mL of hydriodic acid, immediately close the vial tightly, and weigh the contents and the vial accurately. Shake the vial for 30 seconds, heat to 125
for 10 minutes, allow to cool for 2 minutes, shake again for 30 seconds, and heat to 125
for 10 minutes. Afterwards allow to cool for 2 minutes, and repeat shaking and heating for a third time. Allow the vial to cool for 45 minutes, and reweigh. If the loss is greater than 10 mg, discard the mixture and prepare another. Use the upper layer for analysis.
Reference solution—
Transfer 100.0 mg of adipic acid, 4.0 mL of the Internal standard solution and 4.0 mL of hydriodic acid into a suitable 10 mL thick-walled reaction vial with a pressure-tight septum closure. Close the vial tightly, and weigh the vial and contents accurately. Afterwards inject 50 µL of the iodoethane through the septum with a syringe, weight the vial again, and calculate the mass of iodoethane added, by difference. Shake well, and allow the layers to separate.
Chromatographic system (see Chromatography 621)—
The gas chromatograph is equipped with a flame-ionization detector and a 2-mm × 5.0-m stainless steel column packed with 3% G2 on 150-µm to 180-µm mesh support S1A. The carrier gas is nitrogen, flowing at a rate of about 15 mL per minute. The injection port and detector temperatures are both maintained at 200
. The column temperature is maintained at 80
.
Procedure—
Inject 1 µL of the upper layer of the
Reference solution into the chromatograph, record the chromatogram, and record the areas of the peaks. The relative retention times are as follows: iodoethane 0.6, toluene 1.0, and
o-xylene 2.3. Adjust the sensitivity of the system so that the heights of the two principal peaks are at least 50% of the full scale of the recorder. The test is not valid unless the resolution between the peaks corresponding to iodoethane and toluene is at least 2.0. Inject 1 µL of the
Test solution into the chromatograph, and record the chromatogram as directed for
Reference solution. Use the retention times observed in the chromatogram of the
Reference solution to identify the peaks in the chromatogram of the
Test solution. Calculate the percentage of ethoxy groups by the formula:
[451000/312][Q1m2]/[Q2m1(100 – d)],
where
Q1 is the ratio of the iodoethane peak area to the toluene peak area in the chromatogram obtained with the
Test solution; Q2 is the ratio of the iodoethane peak area to the toluene peak area in the chromatogram obtained with the
Reference solution; m1 is the mass of ethylcellulose used in the
Test solution in mg;
m2 is the mass of iodoethane used in the
Reference solution in mg; and
d is the loss on drying as a percentage.
