Chrominfo: Identification test for zinc oxide

Learn the identification test for zinc oxide through a laboratory experiment or practical.

Aim:

To perform identification test for zinc oxide.

Reference: Indian Pharmacopoeia (IP)

Requirements:

Glasswares and miscellaneous:

Test tube, measuring cylinder, pipette, glass rod, volumetric flask, beaker, funnel, dropper, rubber stopper, test tube stand, test tube holder, filter paper, balance, etc.

Chemicals:

Zinc oxide (ZnO), sodium sulphide (Na2S), sodium hydroxide (NaOH), ammonium chloride (NH4Cl), ammonium mercuric thiocyanate (C4H8HgN6S4), cupric sulphate (CuSO4), barium chloride (BaCl2), potassium ferrocyanide (C6FeK4N6), lead acetate (Pb(C2H3O2)2), sulphuric acid (H2SO4), hydrochloric acid (HCl), etc.

Theory:

Identification tests are used to determine the drug's quality so that it can be used safely. This identification of ZnSO4 is usually based on the reactions of ions and cations present in the sample, by which we can determine the quality of the drug.

Zinc oxide has the formula ZnO and is an inorganic substance. It comes as a white amorphous powder that is water-insoluble but soluble in dilute acids and bases. Zinc oxide is used as an ingredient in pharmaceutical ointments to treat skin irritations.

Procedure:

Identification tests for zinc ion:

When heated to a high temperature, the sample turns yellow; However, the yellow color fades as the sample cools.
Take 0.3 gm of zinc oxide and dissolve it in 4.5 ml of 2M HCl, then make up the volume to 15 ml with distilled water. The prepared solution gives the characteristic reaction of zinc salt as follows:

Take 05 ml of the above-prepared solution and add 0.2 ml of NaOH solution, by which a white precipitate is produced.
Take 05 ml of the above-prepared solution and acidify it with a dilute solution of sulphuric acid. Add a drop of cupric sulfate solution (0.1% w/v) and 02.00 ml of ammonium mercuric thiocyanate solution by which a violet precipitate is formed.
Take 05 ml of the above-prepared solution and add 02.00 ml of potassium ferrocyanide solution. This forms a white precipitate that is insoluble in dilute hydrochloric acid.