Separation and identification of Group IIIB cations on the semimicro scale

14 SEPARATION AND IDENTIFICATION OF GROUP IIIB CATIONS ON THE SEMIMICRO SCALE The separation scheme outlined in Table VI. 16 commences with the sulphide precipitates obtained according to the prescriptions of the general separation table (Table VI. 11 in Section VI.9). It is a semimicro adaptation of the hydrochloric acid-hydrogen peroxide method, described in Table V.24 (Section V.15). 

For explanations to the scheme in Table VI. 16 consult the notes to Table V.24 in Section V.15. 

If black, may contain CoS and NiS. Test residue with borax bead. 

Add 10-15 drops dilute HC1 and 5 drops of M NaOCl solution, stir and place in a hot water bath for 1-2 minutes. Transfer the liquid with the aid of 1 ml water to a semimicro boiling tube and boil gently to expel Cl2. Divide the solution into 2 parts. 

Transfer to a semimicro boiling tube, boil to expel H2S (test with lead acetate paper), return liquid to semimicro centrifuge tube, cool, add excess NaOH solution (0-5-1 ml) and 4 drops of 3 per cent H202 solution heat on a water bath for 3 minutes. Centrifuge. 

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