Separation and identification of Group IIIB cations

For the separation of Group IIIB cations two methods are described. The first 

If black, may contain CoS and NiS. Test residue with borax bead. If blue, Co is indicated. 

Dissolve the ppt. in a mixture of 1-5 ml m NaOCl solution and 0-5 ml dilute HC1. Add 1 ml dilute HC1, and boil until all Cl2 is expelled. Cool and dilute to about 4 ml. 

May contain Mn2+ and Zn2+ and, possibly, traces of Co2+ and Ni2 +. Boil until H2S removed (test with lead acetate paper), cool, add excess NaOH solution, followed by 1 ml 3 % H202 solution. Boil for 3 minutes. Filter (3). 

The presence of small amounts of Ni2+ and Co2+ ions in the filtrate (containing Mn2+ and Zn2+ ions) causes no serious intererence in the subsequent tests. 

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VI.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). 

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