Packaging and storage— Preserve in tight containers,and prevent exposure to excessive heat.

Solubility in 70percent alcohol— One volume dissolves in 3volumes of 70percent alcohol,with not more than slight opalescence.

Identification— Mix in a dry test tube 6drops of Oil with 5mLof a 1in 300solution of nitric acid in glacial acetic acid,and place the tube in a beaker of boiling water:within 5minutes the liquid develops a blue color which,on continued heating,deepens and shows a copper-colored fluorescence,and then fades,leaving a golden-yellow solution.

Specific gravity á841ñ: between 0.896and 0.908.

Angular rotation á781Añ: between -18and -32.

Refractive index á831ñ: between 1.459and 1.465at 20.

Heavy metals,Method IIá231ñ: 20µg per g.

Limit of dimethyl sulfide— Distill 1mLfrom 25mLof Oil,and carefully superimpose the distillate on 5mLof mercuric chloride TSin a test tube:a white film does not form at the zone of contact within 1minute.

Assay for total esters— Place about 10g of Oil,accurately weighed,in a 250-mLconical flask,add 10mLof neutralized alcohol and 2drops of phenolphthalein TS,then add,dropwise,0.1Nsodium hydroxide until a faint pink color appears.Add 25.0mLof 0.5Nalcoholic potassium hydroxide VS,connect the flask to a reflux condenser,and heat on a boiling water bath for 1hour.Allow the mixture to cool,add 20mLof water,add phenolphthalein TS,and titrate the excess alkali with 0.5Nhydrochloric acid VS.Perform a blank determination,disregarding the 0.1Nsodium hydroxide (see Residual Titrationsunder Titrimetry á541ñ).Each mLof 0.5000Nalcoholic potassium hydroxide consumed in the saponification is equivalent to 99.15mg of total esters calculated as menthyl acetate (C12H22O2).

Assay for total menthol— Place 10mLof Oil in an acetylation flask of 100-mLcapacity,and add 10mLof acetic anhydride and 1g of anhydrous sodium acetate.Boil the mixture gently for 1hour,accurately timed,cool,disconnect the flask from the condenser,transfer the mixture to a small separator,rinsing the acetylation flask with three 5-mLportions of warm water,and add the rinsings to the separator.When the liquids have completely separated,discard the water layer,and wash the remaining oil with successive portions of sodium carbonate TS,diluted with an equal volume of water,until the last washing is alkaline to phenolphthalein TS.Dry the resulting oil with anhydrous sodium sulfate,and filter.Transfer 5mLof the dry acetylated oil to a tared,100-mLconical flask,and weigh.Add 50.0mLof 0.5Nalcoholic potassium hydroxide VS,connect the flask to a reflux condenser,and boil the mixture on a steam bath for 1hour,accurately timed.Allow the mixture to cool,add 10drops of phenolphthalein TS,and titrate the excess alkali with 0.5Nhydrochloric acid VS.Perform a blank determination (see Residual Titrationsunder Titrimetry á541ñ).Calculate the percentage of total menthol in the Oil tested by the formula: in which Ais the result obtained by subtracting the number of mLof 0.5Nhydrochloric acid required in the above titration from the number of mLof 0.5Nhydrochloric acid required in the residual titration blank,Eis the percentage of esters calculated as menthyl acetate (C12H22O2),and Bis the weight of acetylated oil taken.

Expert Committee:(EMC)Excipients:Monograph Content

USP28–NF23Page 3047

Phone Number:1-301-816-8262