Packaging and storage—
Preserve in well-closed containers.
Identification—
A:
Acidify about 5 g with 25 mL of 2 N sulfuric acid, add 20 mL of water, and extract in a separator with two 25-mL portions of ether. Evaporate the ether solution until the odor of ether no longer is perceptible. Add
potassium permanganate TS dropwise to a 1-mL portion of this residue: the permanganate color is discharged.
B:
A 3-mL portion of the residue of undecylenic acid obtained in Identification test A responds to Identification test B under Undecylenic Acid.
C:
Dissolve about 100 mg in a mixture of 10 mL of water and 1 mL of ammonium hydroxide, and add a few drops of
sodium sulfide TS: a white, flocculent precipitate of zinc sulfide is formed.
Loss on drying 
731
—
Dry it at 105
for 2 hours: it loses not more than 1.25% of its weight.
Alkalies and alkaline earths—
Boil 1.50 g with a mixture of 50 mL of water and 10 mL of hydrochloric acid, filter while hot, and wash the separated acid with about 50 mL of hot water. Render the combined filtrate and washings alkaline with 6 N ammonium hydroxide, add
ammonium sulfide TS to precipitate the zinc completely, dilute with water to 200 mL, mix, and filter. To 100 mL of the clear filtrate add 0.5 mL of sulfuric acid, evaporate to dryness, and ignite over a low flame to constant weight: the weight of the residue does not exceed 7.5 mg (1.0%).
Assay—
Boil 50.0 mL of 0.1 N sulfuric acid VS with about 1 g of Zinc Undecylenate, accurately weighed, for 10 minutes, or until the undecylenic acid layer is clear, adding water, as necessary, to maintain the original volume. Cool, and transfer the mixture, with the aid of water, to a 500-mL separator. Dilute with water to about 250 mL, and extract with two 100-mL portions of solvent hexane. Wash the combined extracts with water until the last washing is neutral to litmus, add the washings to the original water layer, and evaporate on a steam bath to about 100 mL. Cool, add 3 drops of
methyl orange TS, and titrate the excess sulfuric acid with 0.1 N sodium hydroxide VS. Perform a blank determination (see
Residual Titrations under
Titrimetry 541). Each mL of 0.1 N sulfuric acid is equivalent to 21.60 mg of C
22H
38O
4Zn.
;)
