N. S. Poonia and H. K. 1. Gupta Government Ripudoman College Nabha, Puniab, India
I
Separation and Identification of Copper and Cadmium '
Recently nine procedure^'.^ have been published for the identification of copper and cadmium in a mixture of the two. The author has quoted the literature extensively. The present communication describes three semimicro procedures. It is assumed that Hg(II), Pb(II), and Bi(II1) of the copper group of the basic radical scheme of qualitative analysis have been removed by the conventional method leaving an ammoniacal solution containing copper and cadmium. I n all the cases both the ions were finally detected by HzS gas as insoluble sulfides. The concentration of copper and cadmium ions in the solution employed in this investigation was about 1mg/ml. From the slightly acidic solution of copper and cadmium, 3-hydroxy-1,3-dipbenyltriazeneJ precipitates only copper(I1) as a chocolate brown complex, leaving cadmium in the solution. Add 1.0 d l acetic acid to 3 4 drops of solution until the blue color is discharged. Add 3 4 drops of a 1% ethanolic solution of 3-hydroxy-1,3-diphenyltriazene, heat over a waterbath for 1-2 min to coagulate the brown precipitate of copper con~plex,and centrifuge. Test the centrifugate for cadmium. Wash the residue twice with water, add 2-3 drops of concentrated HC1, and heat over a waterbath to dissolve it. Dilute the solution to about 1.5-2.0 ml and confirm the copper. CHANDRA. R.. THIS JOURNAL. 38. 409 (1961). CHANDRA; R.; Sehwl Sei. ~ e " . 43,451'(1961). , a S o ~ N.~ C., ~ ~AND, BRATTACHAUYYA, S. C., Anal. Chem., 28,1616(1956).
If sodium hydroxide solution is added to an ammoniacal solution of copper and cadmium and the resultant solution heated, Cd(I1) is completely precipitated as Cd(OH)*. But the latter drags along with it an appreciable quantity of copper as bluish sodium ~ u p r a t e . ~ It was observed that if the reaction is carried out in the presence of glycine, almost pure Cd(OH)%is precipitated leaving only copper in the solution as an inner complex of gly~ine.~" Add 2-3 drops of lo'% glycine solution and 0.5-1.0 ml of 3 M NaOH solution to 2-3 drops of the blue solution and boil. Cadmium is precipitated as white Cd(OH),. . .From a distinctly acidic solution of copper and cadmium, thiogly~ollanilide~~ precipitates only copper as an inner complex, leaving cadmium in the solution. Add dropwise dilute HC1 to 3 4 drops of the blue solution until deep color just disappears. Add one drop more. Introduce 5-6 drops of the 1% ethanolic solution of thioglycollanilide and heat over a waterbath. A light yellow copper complex separates out. Wash the residue with water, heat it over a waterbath with 1 ml of 6 M HCl until it dissolves, and test for copper. The authors express gratitude to Shri Mohan Singh, Principal, Government Ripudaman College, Nabha, for providing facilities in the college. HUSTED, H. G., THIS JOURNAL, 35, 403 (1958). FEEL. F.. "Chemistm of S~ecific.Selective and Sensitive ~eaetions;"Academic ~ r k s s ,N& ~ & k ,1949, (a) pp. 41, 43; 6
( b ) p. 232.
Volume 41, Number 8, August 1964
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