Confirmatory tests for anions on the semimicro scale

6 CONFIRMATORY TESTS FOR ANIONS ON THE SEMIMICRO SCALE The tests in the preceding section will indicate the anions present. In general, these should be confirmed by at least one distinctive confirmatory test. The following are recommended. Full experimental details will be found in Chapter IV under the reactions of the anions, the reference to these will be abbreviated as follows thus (IV.2, 7) is to be interpreted as Section IV.2, reaction 7. It will of course be realized that the tests in Chapter IV refer to reactions on the macro scale the student should have no difficulty in reducing these to the semimicro scale once the technique described in Section II.4 has 

Chloride. Mix 20 mg of the substance with an equal weight of Mn02 and 0-5 ml concentrated H2S04, and place in the hot water rack Cl2 is evolved (reddens then bleaches litmus paper and also turns potassium iodide-starch paper blue) (IV.14, 2). 

Bromide. Mn02 and concentrated H2S04 test (as under Chloride) Br2 is evolved (IV.15, 2) OR dissolve 20 mg of the substance in 0-5 ml water, add 5 drops of dilute HC1, 5 drops of CC14, and 2-3 drops of NaOCl solution and shake reddish-brown colouration of CC14 layer (IV.15, 5). 

Iodide. NaOCl solution, dilute HC1 and CC14 test (as under Bromide) violet colouration of CC14 layer (IV.16, 4). 

Fluoride. Fit a 4 ml (75 x 10 mm) test-tube with a cork carrying a tube about 8 cm long and of about 3 mm bore cut a V-shaped groove in the cork. Adjust the tube in the cork so that the lower end is about 2-5 cm from the bottom of the test-tube (cf. Fig. V. 1). Place 15-20 mg of the substance and 0-5 ml concentrated H2S04 in the test-tube, dip the glass tube into water so that a film of water almost seals the lower end to a depth of about 5 mm, insert into the test-tube, and place in the hot water rack. The formation of a white film in the water confirms fluoride (IV 17, 1). 

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