In the filtrate of the first group add 1-2 mL of dil HCl, heat the content and pass H2S gas in warm
solution. Filter the solution. Repeat the above process of (i.e. dilution, heating and passing H2S
gas) with filtrate until no more precipitate is formed. Filter it again and take the whole precipitate
for analysis of II group and keep the filtrate for the analysis of III group. Wash the precipitate
with a small volume of 5% NH4Cl that has been saturated with the H2S and transfer in a
porcelain dish. Add 5-10 mL of ammonium polysulphide solution, heat the solution up to 60 °C
and maintain at this temperature for 3-4 minutes with constant stirring. Filter the solution.
Residue: The residue may contain HgS, PbS, Bi2S3, CuS, CdS, PdS along with traces of
sulphides of Au, Pt, Mo and Sn. Group II A present. It is also called the copper group.
Filtrate: The solution may contain the soluble thio salts of As, Sb, Sn, Mo, Se and Te. Acidify
the solution by drop wise addition of HCl (test with litmus paper). Formation of a coloured
precipitate indicates the presence of Group IIB.
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