T. R. Williams and Frederick BurlonL
The College of Wooster Wooster. Ohio
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A Specific Qualitative Reagent for Copper
The separation and confirmation of copper, particularly in samples containing cadmium, often cause trouble in the conventional qualitative analysis scheme. We are here suggesting the use of a specific precipitant for separation and confirmation of copper(11)ions. Billman2 has used o-(p-tolurlsulfonamide) aniline, (T-sulfonamidine)
for the quantitative determinxtion of copper in brass. 'This work is taken in part from the senior independent study of Frederick Burton. 'BILLMAN, J. H., JANETOF, X. S., and CAERNIN, R., Anal. Chem., 32, 1942 (1960).
The precipitation of copper with T-sulfonamidine is quantitative over the pH range 6.2 to 8.5. A solution suspected of containing copper is adjusted to a pH of about 7 (Hydrion paper) by the addition of HCl or NH3. The hydrolysis products of cations such as bismnth, mercury, antimony or silver are removed by centrifuging. The resvlting solution is treated with a few drops of T-sulfonamidine: the appearance of a green precipitate confirms the presence of copper. Solutions as dilute as 0.001 Af in Cu++ may be detected using this reagent but those less than 0.01 M are slow to precipitnte and thus require heating. The separation of mixtures of copper and cadmium may be easily performed in this way. If cadmium is present in the resulting solutio11, yellow CdS may be precipitated by thioacetamide. None of the cat,ions most commonly present in a qualit,ative analysis scheme interfere with this test.
Volume 38, Number 8, August 1961
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