Separation and identification of Group IIA cations

For the separation and identification of Group IIA cations (Hg2+, Pb2+, Bi3+, Cu2+, and Cd2+) two, somewhat different methods are recommended. From the reagents used, these are called (a) sulphuric acid method and (b) sodium hydroxide method. 

Dissolve in a mixture of of m NaOCl solution and 0-5 ml of dilute HC1. Add 1 ml dilute HC1, boil off excess Cl2 and cool. Add SnCl2 solution. 

May contain nitrates of Pb, Bi, Cu, ond Cd. Test a small portion for Pb by adding dilute H2S04 and alcohol. A white ppt. of PbS04 indicates Pb present. If Pb present, add dilute H2S04 to the remainder of the solution, concentrate in the fume cupboard until white fumes (from the dissociation of the H2S04) appear. Cool, add 10 ml of water, stir, allow to stand 2-3 minutes, filter and wash with a little water. 

Add concentrated NH3 solution until solution is distinctly alkaline. Filter (4). 

White may be Bi(OH)3. Wash. Dissolve in the minimum volume of dilute HC1 and pour into cold sodium tetrahydroxo-stannatefll). 

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VL11 SEPARATION OF GROUPS IIA AND IIB AND SEPARATION AND IDENTIFICATION OF GROUP IIA CATIONS When describing these separations in macro scale, two alternative methods have been suggested (see Section V.10), one being based on the use of ammonium polysulphide (see Table V.14) and the other on potassium hydroxide (Table V.15). In semimicro scale the potassium hydroxide method is more suitable and this will be presented here. This does not mean however that the ammonium polysulphide... 

Table VII.3 Separation and identification of Group IIA cations in the presence of Pt. Au,...

VI.12 SEPARATION AND IDENTIFICATION OF GROUP IIB CATIONS ON THE SEMIMICRO SCALE For this separation the centrifugate from Group IIA is used. The separation scheme outlined in Table VI. 14 is therefore linked directly to Table VI in Section VI.11. If the ammonium polysulphide method has been adopted for the separation of Groups IIA and IIB, the student should scale down the scheme given in Table V.18 (Section V.12) to semimicro scale. 

VII.14 SEPARATION AND IDENTIFICATION OF GROUP II CATIONS IN THE PRESENCE OF MOLYBDENUM, GOLD, PLATINUM, PALLADIUM, SELENIUM, AND TELLURIUM The first step in this separation process is to separate cations into Groups IIA and IIB. 

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