Studies of the collection of copper and zinc by co-precipitation with manganese dioxide are reported. The collection of copper is shown to be small under all conditions studied; that of zinc is negligible.Further studies of the collection of lead and tin are presented, and a method for their separate and simultaneous determination is described. The virtual non-collection of copper and zinc is used as a basis for the application of these methods to the determination of lead and tin in copper-base alloys.The collection of lead and tin is made from a 0-008 M acidic solution containing ethanol to hold the tin in solution. After dissolution of the precipitate, tin and lead are determined together by polarography in acidic chloride solution.Lead is then determined alone by polarography in alkaline mannitol solution and the tin content found by difference.Results are presented and some aspects discussed.THE use of manganese dioxide, produced by the reaction of manganese(I1) ion with potassium permanganate, as a "collector" for the co-precipitation of metals was first described by Blumentha1,l who used it for antimony. He indicated that the procedure could also be applied to bismuth and tin. Kallman and Prestira2 showed that the precipitation of bismuth was incomplete in acidic solutions of concentration greater than 0.07 N. Previous work by one of us has shown that antimony and tin are collected over a wide range of acid concentrations. Similar results have been obtained by Babko and Shtoka10.~ Several analytical applications have been reported, for example, the determination of antimony with Rhodamine B by MacNulty and Woollard,4 antimony in copper by Park and Lewis,s antimony and bismuth in anode copper by Yamazaki,B arsenic and tin in lead by Luke7 and antimony in cast iron by Rooney.8 No previous comprehensive study has, however, been made of the elements to which the procedure can be applied, or the concentration range or conditions in which it is efficient for each species.The present work was undertaken to provide a comprehensive study, as mentioned above. Previous papers in the series have established conditions and concentration ranges for the "collection" of antimony, bismuth and tin,g and for tin and 1ead.lO In the present work, studies of copper and zinc have been made and further information on the behaviour and determination of lead and tin is presented.
EXPERIMENTALThe "collection" procedure previously describedg Treat the sample solution, in a 400-ml beaker, with sufficient nitric acid solution to make the volume up to 200m1, add 5 m l of 5 per cent. manganese(I1) sulphate solution and heat to boiling, then add 2-5 ml of 1.25 per cent. potassium permanganate solution, dropwise, and continue boiling for a further 2 minutes. Allow the solution to stand a t a was used in all experiments.* For details of Parts I and I1 of this series, see reference list, p. 382.
