» Petrolatum is a purified mixture of semisolid hydrocarbons obtained from petroleum. It may contain a suitable stabilizer.
Packaging and storage— Preserve in well-closed containers.
Labeling— Label it to indicate the name and proportion of any added stabilizer.
Color— Melt about 10 g on a steam bath, and pour about 5 mL of the liquid into a clear-glass 15- × 150-mm test tube, keeping the petrolatum melted. The petrolatum is not darker than a solution made by mixing 3.8 mL of ferric chloride CS and 1.2 mL of cobaltous chloride CS in a similar tube, the comparison of the two being made in reflected light against a white background, the petrolatum tube being held directly against the background at such an angle that there is no fluorescence.
Specific gravity 841: between 0.815 and 0.880 at 60.
Melting range, Class III 741: between 38 and 60.
Apparatus— Determine the consistency of Petrolatum by means of a penetrometer fitted with a polished cone-shaped metal plunger weighing 150 g, having a detachable steel tip of the following dimensions: the tip of the cone has an angle of 30, the point being truncated to a diameter of 0.381 ± 0.025 mm, the base of the tip is 8.38 ± 0.05 mm in diameter, and the length of the tip is 14.94 ± 0.05 mm. The remaining portion of the cone has an angle of 90, is about 28 mm in height, and has a maximum diameter at the base of about 65 mm. The containers for the test are flat-bottom metal cylinders that are 100 ± 6 mm in diameter and not less than 65 mm in height. They are constructed of at least 1.6-mm (16-gauge) metal, and are provided with well-fitting, water-tight covers.
Procedure— Place the required number of containers in an oven, and bring them and a quantity of Petrolatum to a temperature of 82 ± 2.5, pour the Petrolatum into one or more of the containers, filling to within 6 mm of the rim. Cool to 25 ± 2.5 over a period of not less than 16 hours, protected from drafts. Two hours before the test, place the containers in a water bath at 25 ± 0.5. If the room temperature is below 23.5 or above 26.5, adjust the temperature of the cone to 25 ± 0.5 by placing it in the water bath.
Without disturbing the surface of the substance under test, place the container on the penetrometer table, and lower the cone until the tip just touches the top surface of the test substance at a spot 25 mm to 38 mm from the edge of the container. Adjust the zero setting and quickly release the plunger, then hold it free for 5 seconds. Secure the plunger, and read the total penetration from the scale. Make three or more trials, each so spaced that there is no overlapping of the areas of penetration. Where the penetration exceeds 20 mm, use a separate container of the test substance for each trial. Read the penetration to the nearest 0.1 mm. Calculate the average of the three or more readings, and conduct further trials to a total of 10 if the individual results differ from the average by more than ±3%: the final average of the trials is not less than 10.0 mm and not more than 30.0 mm, indicating a consistency value between 100 and 300.
Acidity— If the addition of phenolphthalein TS in the test for Alkalinity produces no pink color, add 0.1 mL of methyl orange TS: no red or pink color is produced.
Alkalinity— Introduce 35 g into a suitable beaker, add 100 mL of boiling water, cover, and place on a stirring hot-plate maintained at the boiling point of water. After 5 minutes, allow the phases to separate. Draw off the separated water into a casserole, wash the petrolatum further with two 50-mL portions of boiling water, and add the washings to the casserole. To the pooled washings add 1 drop of phenolphthalein TS, and boil: the solution does not acquire a pink color.
Residue on ignition 281 Heat 2 g in an open porcelain or platinum dish over a Bunsen flame: it volatilizes without emitting an acrid odor and on ignition yields not more than 0.1% of residue.
Organic acids— Weigh 20.0 g, add 100 mL of a 1 in 2 mixture of neutralized alcohol and water, agitate thoroughly, and heat to boiling. Add 1 mL of phenolphthalein TS, and titrate rapidly with 0.1 N sodium hydroxide VS, with vigorous agitation to the production of a sharp pink endpoint, noting the color change in the alcohol-water layer: not more than 400 µL of 0.100 N sodium hydroxide is required.
Fixed oils, fats, and rosin— Digest 10 g with 50 mL of 5 N sodium hydroxide at 100 for 30 minutes. Separate the water layer, and acidify it with 5 N sulfuric acid: no oily or solid matter separates.
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Monograph Hong Wang, Ph.D.
(EM205) Excipient Monographs 2
USP32–NF27 Page 3263
Pharmacopeial Forum: Volume No. 28(2) Page 569