Resacetophenone Oxime Chelation
S. G. Kadarmandalgi Karnatak University ~ h ~ ~ India ~ ~
~
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3
of, Copper in the Presence of Cadmium
The use of resacetophenone oxime as a chelating agent for copper(I1) ions avoids the use if cyanide in the separation of copper from cadmium ions. The method proposed here is rapid, highly sensitive, and provides distinct colors for confirmation of the ions. Ephraiuml suggested that copper(I1) forms a yellowish-brown precipitate with resacetophenone oxime in slightly acidic medium; however cadmium(I1) does not react with resacetophenone oxime in acidic medium. The copper-resacetophenone oxime is insoluble in acetic acid medium and can be removed easily by filtration or centrifugation. Cadmium is then identifiable as usual by passing hydrogen sulfide in the clear filtrate. The separation of copper and the identification of cadmium is simple and reliable. The method assumes that a traditional scheme of qualitative analysis is used to precipitate Cd(II), Cu(lI), Bi(III), and Pb(I1) as their sulfides from acid solution. The sulfides are then boiled with dilute nitric acid, and Pb(I1) is removed as PbS04. The filtrate after the separation of PbSOais treated with excess of ammonia so that Bi(II1) is precipitated as Bi(OH), and Cu(I1) and Cd(I1) ions form soluble complexes Cu(NH&++and Cd(NHJ,++ respectively. The solution containing Cu(NH&++ and Cd(NH&++ complex ions is boiled vigorously for a few minutes to expel excess of ammonia. After cooling, add dilute acetic acid ( 4 6 N ) drop by drop until the deep blue color changes to pale green; then add 2-3 drops more. To the above solution add a few drops of 10yo ammonium acetate solution until the resulting solution has a pH of 4-5 (indicator papers) and boil. To the hot solution add 0.5% resacetophenone oxime in acetic acid drop-by-drop until there is no further precipitation. The yellowish-brown precipitate of copper-resacetophenone
' EPHRNWM, F., Chem.Ber., 64, 1210 (1931).
438 / Journal o f Chemical Education
oxime is easily removed by filtration. Test the filtrate with the reagent for complete precipitation. After completely removing the copper complex, the clear colorless filtrate is saturated with hydrogen sulfide. A yellow precipitate confirms the presence of cadmium. If copper is absent no brown precipitate will form, and if cadmium is absent no yellow precipitate will form. The solid resacetophenone oxime is prepared by reflnxing resacetophenone (in alcohol) with hydroxylamine hydrochloride. The oxime is further purified by crystallization with ethanol. A 0.5% solution of the reagent is prepared by dissolving 0.5 g of oxime in 20 ml of glacial acetic acid and diluting to 100 ml with distilled water. The reagent can be prepared as follows:
I
OH Resorcinol Acetic acid Resacetophenone CH1
I
ONOH
(Y OH
Resscetophenone oxime
The author thanks Dr. S. Siddappa, Professor of Chemistry, and Dr. N. S. Biradar for interest and encouragement.
