»Zinc Undecylenate contains not less than 98.0percent and not more than 102.0percent of C22H38O4Zn,calculated on the dried basis.
Packaging and storage
Preserve in well-closed containers.
Acidify about 5g with 25mLof 2Nsulfuric acid,add 20mLof water,and extract in a separator with two 25-mLportions of ether.Evaporate the ether solution until the odor of ether no longer is perceptible.Add potassium permanganate TSdropwise to a 1-mLportion of this residue:the permanganate color is discharged.
A3-mLportion of the residue of undecylenic acid obtained in Identification
responds to Identification
under Undecylenic Acid.
Dissolve about 100mg in a mixture of 10mLof water and 1mLof ammonium hydroxide,and add a few drops of sodium sulfide TS:a white,flocculent precipitate of zinc sulfide is formed.
Loss on drying á731ñ
Dry it at 105
for 2hours:it loses not more than 1.25%of its weight.
Alkalies and alkaline earths
Boil 1.50g with a mixture of 50mLof water and 10mLof hydrochloric acid,filter while hot,and wash the separated acid with about 50mLof hot water.Render the combined filtrate and washings alkaline with 6Nammonium hydroxide,add ammonium sulfide TSto precipitate the zinc completely,dilute with water to 200mL,mix,and filter.To 100mLof the clear filtrate add 0.5mLof sulfuric acid,evaporate to dryness,and ignite over a low flame to constant weight:the weight of the residue does not exceed 7.5mg (1.0%).
Boil 50.0mLof 0.1Nsulfuric acid VSwith about 1g of Zinc Undecylenate,accurately weighed,for 10minutes,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-mLseparator.Dilute with water to about 250mL,and extract with two 100-mLportions 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 100mL.Cool,add 3drops of methyl orange TS,and titrate the excess sulfuric acid with 0.1Nsodium hydroxide VS.Perform a blank determination (see Residual Titrations
under Titrimetry á541ñ
).Each mLof 0.1Nsulfuric acid is equivalent to 21.60mg of C22
:Behnam Davani,Ph.D.,MBA,Senior Scientist
:(PA7)Pharmaceutical Analysis 7