Packaging and storage—
Prepare in tight containers.
Identification—
A:
The solution prepared for measurement of absorbance in the Assay exhibits a maximum at 277 ± 3 nm.
B:
To about 10 mg contained in a small test tube add 10 mg of resorcinol, mix, add 0.5 mL of sulfuric acid, and heat in a liquid bath at 160
for 3 minutes. Cool, and pour the solution into a mixture of 25 mL of 1 N sodium hydroxide and 200 mL of water: the solution shows a vivid green fluorescence.
C:
Dissolve about 2 g in 20 mL of methanol, and pour 1 mL of the solution onto a clear glass plate: a film is deposited as the methanol evaporates.
Viscosity 
911
—
Dissolve a quantity, equivalent to 15 g on the anhydrous basis, in 85 g of methanol. Determine the viscosity of this solution, using a capillary viscosimeter. The apparent viscosity is between 7 and 11 centipoises, determined at 25 ± 0.2
.
Free phthalic acid—
Standard preparation—
Transfer about 50 mg of phthalic anhydride, accurately weighed, to a 1000-mL volumetric flask, dissolve in water, dilute with water to volume, and mix.
Test preparation—
Dissolve about 1500 mg of Polyvinyl Acetate Phthalate, accurately weighed, in 50 mL of a mixture of methylene chloride and methanol (4:1). Transfer the solution to a separator with the aid of 75 mL of water, and swirl, taking care not to shake. Add 100 mL of hexanes, shake, and allow the mixture to stand until it separates into 2 layers. Transfer the water layer to a 250-mL volumetric flask. Add 100 mL of water to the separator, shake, and allow to stand until the layers separate. Transfer the water layer to the same volumetric flask, dilute with water to volume, and mix. If the solution is cloudy, centrifuge a portion until clear.
Procedure—
Concomitantly determine the absorbances of the
Standard preparation and the
Test preparation in 1-cm cells at the wavelength of maximum absorbance at about 277 nm. Calculate the percentage of free phthalic acid taken by the formula:
25(166.13 / 148.12)(WS / WU)(AU / AS),
in which 166.13 and 148.12 are the molecular weights of phthalic acid and phthalic anhydride, respectively;
WS and
WU are the weights, in mg, of phthalic anhydride and Polyvinyl Acetate Phthalate, respectively; and
AU and
AS are the absorbances of the
Test preparation and the
Standard preparation, respectively. Not more than 0.6%, on the anhydrous basis, is found.
Free acid other than phthalic—
Proceed as directed for
Test preparation under
Free phthalic acid, but instead of transferring the water extracts to a volumetric flask, transfer them to a 400-mL beaker, and titrate with 0.1 N sodium hydroxide VS to a phenolphthalein endpoint. Calculate the volume,
Vp, in mL, of 0.1 N sodium hydroxide consumed by the free phthalic acid in the specimen taken by the formula:
(1 / 830.6)pW,
in which
p is the percentage of free phthalic acid, previously determined; and
W is the weight, in mg, of the specimen, on the anhydrous basis. Calculate the percentage of free acid other than phthalic, as acetic acid, taken by the formula:
60.05(10 /
W)(
V 
Vp),
in which
V is the total volume, in mL, of 0.1 N sodium hydroxide used. Not more than 0.6%, on the anhydrous basis, is found.
Phthalyl content—
Standard preparation—
Transfer 50 mg of phthalic anhydride, accurately weighed, to a 1000-mL volumetric flask, dissolve with heat in 100 mL of alcohol, dilute with alcohol to volume, and mix.
Assay preparation—
Transfer about 100 mg of Polyvinyl Acetate Phthalate, accurately weighed, to a 1000-mL volumetric flask, dissolve in alcohol, dilute with alcohol to volume, and mix.
Procedure—
Concomitantly determine the absorbances of the
Standard preparation and the
Assay preparation in 1-cm cells at the wavelength of maximum absorbance at about 275 nm. Calculate the percentage of phthalyl, on the acid-free basis, taken by the formula:
100(WS / WU)(AU / AS),
in which
WS and
WU are the weights, in mg, of phthalic anhydride and Polyvinyl Acetate Phthalate on the anhydrous basis, respectively; and
AU and
AS are the absorbances of the
Assay preparation and the
Standard preparation, respectively.
