Scrutiny of copper ions by precipitating the hydrated copper (II) sulfate with oxine

Oxine is an 8-hydroxy-quinoline organic compound. When reacted with Cu (II) or other metallic ions it behaves like a monoprotic acid and a metal complex is formed. The composition of the complex formed when hydrated copper (II) sulfate is reacted with oxine is Cu (C₉H₆ON) ₂ with 351.85g/mole formula weight.

The following steps are followed:

1. Approximately 3g hydrated copper sulfate is weighed to the closest milligram.
2. The copper sulfate is dissolved in 100ml of water that is distilled and contained in a big beaker.
3. 5ml of acetic acid (glacial) is added and 1.5g of ammonium acetate is also added.
4. The solution is heated in a hot plate toward approximately 75⁰C.
5. 3% oxine (in ethanol and water in the ratio 95:5) is added drop wise while stirring awaiting completion of the precipitation and the reagent is in excess. Approximately 17-20 milliliters of the oxine solution are needed for this experiment.
6. For 5 minutes, and at 65-70⁰C the mixture is heated and then stirred vigorously, after which the precipitate is allowed to settle. If adequate reagent is used the resultant liquid will be orange-yellow or yellow in color.
7. A filter paper is folded and weighed and a beaker is labeled with grease pencil.
8. The filter paper is placed in a glass funnel placed on an Erlenmeyer flask.
9. A large amount of the liquid is decanted into the filter set up. The remaining mixture is stirred and filtered.
10. Using hot water the residue and the beaker are washed.
11. A rubber policeman is used to scrub the beaker.
12. The residue is transferred to a small beaker or casserole which is dry, clean and has been weighed previously.
13. The beaker or casserole is covered with aluminum foil which is perforated and the system is allowed to dry.
14. Weight of product, after drying is used to get the percentage of copper.

Determination of the amount of water in hydrated copper (II) sulfate.

In this experiment, care should be taken because crucibles that are cold and those that are hot look alike.