Dennis Berk ond ~awrenceHeckerl Cass Technical High School Detroit, Michigan
The Detection of Acetate Ions in Qualitative Analysis
Although several tests for the acetate ion are currently in use, none of these is very reliable. The characteristic odor, either of the acid itself or its ester (after addition of HsSOa and amyl or ethyl alcohol), is often obscure. The basic ferric acetate test is not reliable since hydrolysis of the ferric chloride may occur. Many anions interfere with the simple litmus paper test for volatilized acetic acid. A reliable test for acetate has been developed which is based upon the fact that acetate ion pyrolyzes with sodium hydroxide t o form sodium carbonate. The pyrolyzed unknown is acidified, and effervescence indicates the presence of acetate in the original sample. Other anions, such as C03=,S203=,C204=, C4H106=and the cyanides, give a similar test. These are removed by precipitation with Ca(NO&AgNOa solution. The rollowing procedure is recommended: Procedure. To 10-15 drops of unknown, add 3N
414 / Journal o f Chemical Education
NaOH until slightly basic. Add Ca(NOa)-AgNOa solution, centrifuge and discard the residue. Check the centrifugate for complete precipitation. Add sodium chloride solution to remove excess silver ion, and again centrifuge and discard the residue. Reduce the centrifugate volume to ten drops by evaporation, then transfer to a crucible and add ten drops 3N NaOH solution. Cover the crucible and heat gently to dryness (two minutes). Then heat strongly one additional minute. Let cool, then remove the cover and add a few drops 6N HC1. Effervescence identifies acetate. This test is sensitive to 5 mg of acetate ion. Editor'sNote: This note was submitted by Professor Richard B. Hahn of Wayne State University who says, "Recently Mr. Berk and Mr. Hecker, students a t Cass Techniod High School, told me that they had developed a new test for acetate ion. I was impressed by their originality, enthusiasm and systematic investigation of the problem and urged their submission of this note to the J O ~ I N A OF L CHEMICA~ EDUCATION."
