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401
:
If the substance under test is plastic or semisolid, soften the Lecithin by warming it briefly at a temperature not exceeding 60
, and then mix. Transfer about 2 g, accurately weighed, to a 250-mL conical flask, and dissolve it in 50 mL of solvent hexane. To this solution add 50 mL of alcohol, previously neutralized to phenolphthalein with 0.1 N sodium hydroxide, and mix. Add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS to a pink endpoint that persists for 5 seconds. Calculate the number of mg of potassium hydroxide required to neutralize the free acids in 1.0 g of the specimen by multiplying the number of mL of 0.1 N sodium hydroxide VS consumed in the titration by 5.6 and dividing the result by the weight, in g, of the test specimen: not more than 36 mg of potassium hydroxide are required to neutralize the free acids.
921:
not more than 1.5%.
, and then mix. Weigh 10.0 g into a 250-mL conical flask, add 100 mL of solvent hexane, and shake until solution is apparently complete or until no more of any residue seems to be dissolving. Filter through a coarse-porosity filtering funnel that previously has been heated at 105 for 1 hour, cooled, and weighed, wash the flask with two 25-mL portions of solvent hexane, and pour both washings through the funnel. Dry the funnel at 105 for 1 hour. [Caution—Hexane is flammable.
] Cool to room temperature, and determine the gain in weight: not more than 0.3% is found.
251:
0.001%.
231:
20 µg per g.
467:
meets the requirements.
, and then mix. Transfer about 2 g to a 40-mL centrifuge tube that previously has been tared with a stirring rod, cool, and weigh accurately. Add 15.0 mL of acetone, warm carefully in a water bath to melt the test specimen without evaporating the acetone, but with stirring to aid complete disintegration, and place in an ice-water bath for 5 minutes. Add acetone that previously has been chilled to 0 to 5 to the 40-mL mark on the tube, stirring during the addition. Cool in an ice-water bath for 15 minutes, stir, remove the rod, clarify by centrifuging at about 2000 rpm for 5 minutes, and decant. Break up the residue with the stirring rod, and refill the centrifuge tube to the 40-mL mark with chilled acetone, while stirring. Cool in an ice-water bath for 15 minutes, stir, remove the rod, centrifuge, and decant. Break up the residue with the stirring rod. Place the tube in a horizontal position until most of the acetone has evaporated, mix again, and heat the tube containing the acetone-insoluble residue and the stirring rod at 105 to constant weight. [Caution—Acetone is flammable.
] Determine the weight of the residue, and calculate the percentage of acetone-insoluble matter.
467:
meets the requirements.