Propionic Acid

Propionic Acid USP NF Grade

Propionic Acid contains not less than 99.5 percent and not more than 100.5 percent, by weight, of C3H6O2.

Specific gravity: between 0.988 and 0.993.
Distilling range: between 138.5 and 142.5 .
Heavy metals: To the residue obtained in the test for Nonvolatile residue add 8 mL of 0.1 N hydrochloric acid, warm gently until solution is complete, dilute with water to 100 mL, and use 10 mL of the solution: the limit is 0.001%.
Limit of nonvolatile residue: Evaporate 20 g in a tared dish, and dry at 105 for 1 hour: the weight of the residue does not exceed 2.0 mg.
Readily oxidizable substances: Dissolve 15 g of sodium hydroxide in 50 mL of water, cool, add 6 mL of bromine, stirring to effect complete solution, and dilute with water to 2000 mL. Transfer 25.0 mL of this solution to a glass-stoppered, 250-mL conical flask containing 100 mL of water, and add 10 mL of sodium acetate solution (1 in 5) and 10.0 mL of Propionic Acid. Allow to stand for 15 minutes, add 5 mL of potassium iodide solution (1 in 4) and 10 mL of hydrochloric acid, and titrate with 0.1 N sodium thiosulfate VS just to the disappearance of the brown color. Perform a blank determination. The difference between the volume of 0.1 N sodium thiosulfate required for the blank and that required for the test specimen is not more than 2.2 mL.
Limit of aldehydes: Transfer 10.0 mL to a glass-stoppered, 250-mL conical flask containing 50 mL of water and 10.0 mL of sodium bisulfite solution (1 in 80), insert the stopper, and shake vigorously. Allow the mixture to stand for 30 minutes, then titrate with 0.1 N iodine to the same brownish yellow endpoint obtained with a blank treated with the same quantities of the same reagents. The difference between the volume of 0.1 N iodine required for the blank and that required for the test specimen is not more than 1.75 mL.

Assay: Mix about 1.5 g of Propionic Acid, accurately weighed, with 100 mL of recently boiled and cooled water in a 250-mL conical flask, add phenolphthalein, and titrate with 0.5 N sodium hydroxide to the first appearance of a faint pink endpoint that persists for not less than 30 seconds.

Each mL of 0.5 N sodium hydroxide is equivalent to 37.04 mg of C3H6O2.