A. Separation of Hydroxide Precipitates from Amphoteric Hydroxides:
B. Test for Manganese Ion:
|C. Test for Iron Ion:|
1. To the Solution from part B.1 add 10 drops of 2M NH4Cl. Take your test tube to the fume hood, and add concentrated NH3 drop by drop until the solution is basic to red litmus. At that point add one more drop of NH3 to ensure complete complexing of the Nickel ions. Centrifuge, decant the supernatant to a clean test tube, and save it for the next test in part D.
|D. Test for Nickel Ion:|
1. To the supernatant from part C.1 add 3 drops dimethylglyoxime solution. A brick red precipitate confirms the presence of nickel.
|E. Test for Aluminum Ion:|
1. To the supernatant from A.1 add drops of 6M HNO3 until the solution is acid to blue litmus. At that point add 6M NH3 drop by drop until the solution is basic to red litmus. Once this happens, add 5 more drops of NH3 and heat in a hot water bath for 5 minutes. Centrifuge and decant the supernatant into a clean test tube. Save this supernatant for the next test in part F.
2. Wash the precipitate from E.1 with 1 mL hot deionized water, centrifuge, and discard the washings. Repeat the wash once more. Now, add 6M HNO3 drop by drop until the precipitate just dissolves. Agitate after each drop. Once the precipitate has dissolved, add 2 drops aluminon and stir. Then add 6M NH3 drop by drop until the solution is basic to red litmus and a precipitate reforms. Centrifuge. A pink or red precipitate in a colorless solution confirms the presence of aluminum.
|F. Test for Zinc Ion:|
1. To the supernatant from E.1, add 6M HCl drop by drop until the solution is acid to blue litmus. At that point, add 3 drops O.2M K4[Fe(CN)6] and agitate the solution. Centrifuge if necessary. A very light green precipitate confirms the presence of zinc.
All contents copyrighted (c) 1998
Peter Jeschofnig, Ph.D., Professor of Science, Colorado Mountain College
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