A: Afiltered solution (1in 20)in 3Nhydrochloric acid responds to the tests for Calcium á191ñ.

B: Transfer 40mLof water and 10g of calcium undecylenate to a 250-mLseparator.Cautiously and slowly add 10mLof hydrochloric acid,while swirling.Insert the stopper,and shake.[NOTE—The separator will become quite warm,and pressure must be carefully and frequently relieved through the stopcock.If a curdy,white material remains after 5minutes of shaking,add additional hydrochloric acid,1mLat a time,and shake until a clear oily phase is formed.]Allow the phases to separate,drain,and discard the bottom aqueous layer.Drain and discard the middle oily layer,if present.Filter the top layer of undecylenic acid through a pledget of cotton into a 10-mLgraduated cylinder,noting the volume obtained.Transfer the filtrate to a 250-mLflask,and add an equal volume of aniline.Reflux for 1hour,swirling the flask occasionally.Allow to cool,and pour 60mLof alcohol through the condenser into the flask.Remove the flask from the condenser,add 1g of charcoal,and stir.Filter the slurry into a 250-mLbeaker.Add water dropwise until a few crystals form or the solution becomes slightly cloudy.[NOTE—If too much water is added,an oil will form.Add alcohol dropwise until the oil dissolves.]Allow the mixture to stand or refrigerate until crystals are formed.Collect the crystals on a filter paper inserted in a 45-mm porous glass filter funnel.Wash the crystals with 75mLof 25%alcohol:the crystals have a clean,white,glossy appearance.If not,recrystallize by dissolving the crystals in about 50mLof alcohol.Add about 1g of charcoal,stir,filter into a 150-mLbeaker,and continue as directed above,beginning with “Add water dropwise.”Dry the crystals in vacuum at 50for 2hours:the crystals so obtained melt between 66and 67.5,the procedure for Class Iabeing used (see Melting Range or Temperature á741ñ).[NOTE—If the melting point is low,additional drying or recrystallization may be necessary.]