Packaging and storage—
Package it in rolls of not more than 500 g of a continuous lap, with a light-weight paper running under the entire lap, the paper being of such width that it may be folded over the edges of the lap to a distance of at least 25 mm, the two together being tightly and evenly rolled, and enclosed and sealed in a well-closed container. It may be packaged also in other types of containers if these are so constructed that the sterility of the product is maintained.
Labeling—
Its label bears a statement to the effect that the sterility cannot be guaranteed if the package bears evidence of damage or if the package has been opened previously.
Acidity or alkalinity—
Thoroughly saturate about 10 g with 100 mL of recently boiled and cooled water, then with the aid of a glass rod press out two 25-mL portions of the water into white porcelain dishes. To one portion add 3 drops of phenolphthalein TS, and to the other portion add 1 drop of
methyl orange TS: no pink color develops in either portion.
Residue on ignition 
281
—
Place about 5 g, accurately weighed, in a porcelain or platinum dish, and moisten with 2 N sulfuric acid. Gently heat the cotton until it is charred, then ignite more strongly until the carbon is completely consumed: not more than 0.20% of residue remains.
Water-soluble substances—
Place 10 g, accurately weighed, in a beaker containing 1000 mL of water, and boil gently for 30 minutes, adding water as required to maintain the volume. Pour the water through a funnel into another vessel, and press out the excess water from the cotton with a glass rod. Wash the cotton in the funnel with two 250-mL portions of boiling water, pressing the cotton after each washing. Filter the combined extract and washings, and wash the filter thoroughly with hot water. Evaporate the combined extract and washings to a small volume, transfer to a tared porcelain or platinum dish, evaporate to dryness, and dry the residue at 105
to constant weight: the residue weighs not more than 35 mg (0.35%).
Fatty matter—
Pack 10 ± 0.01 g in a Soxhlet extractor provided with a tared receiver, and extract with ether for 5 hours at a rate such that the ether siphons over not less than four times per hour. The ether solution in the flask shows no trace of blue, green, or brownish color. Evaporate the extract to dryness, and dry at 105
for 1 hour: the weight of the residue does not exceed 70 mg (0.7%).
Dyes—
Pack about 10 g in a narrow percolator, and extract slowly with alcohol until the percolate measures 50 mL: when observed downward through a column 20 cm in depth, the percolate may show a yellowish color, but neither a blue nor a green tint.
Other foreign matter—
The pinches of it taken for the determination of
Fiber length contain no oil stains or metallic particles.
Fiber length and Absorbency—
Remove it from its wrappings, and condition it for not less than 4 hours in a standard atmosphere of 65 ± 2% relative humidity at 21 ± 1.1
(70 ± 2
F), before determining the
Fiber length and
Absorbency.
Fiber length—
Determine the fiber length of Purified Cotton as directed under
Cotton—Fiber Length 691: not less than 60% of the fibers, by weight, are 12.5 mm or greater in length, and not more than 10% of the fibers, by weight, are 6.25 mm or less in length.
Absorbency—
Proceed as directed under
Cotton—Absorbency Test 691: submersion is complete in 10 seconds at a temperature of 25
, and the cotton retains not less than 24 times its weight of water.
