1. GROUP II CATIONS SUPERNATANT A: AsO3-3, AsS3-3, SbO2-, SbS2-, SnO2-2
Dissolve in 16 drops of aqua regia.
Dry it up in a cruicible
Dissolve it in 2-3 mL distilled water and pour it onto a cupper wire. Hg test is positive if the cupper is covered with gray colored Hg.
PRECIPITATE B: HgS
Wash precipitate
Add 20 drops of NH4CH3COO, 6 drops of 6 M CH3COOH and 4 drops of 1M K2CrO4. Pb test is positive if yellow precipitates are formed.
PRECIPITATE D: Bi(OH)3
Add 10 drops of Na2SnO2. Bi test is positive if the color of precipitate turns to black.
PRECIPITATE A: HgS, CuS, CdS, PbS, Bi2S3
GROUP II CATIONS
40 drops of sample
4 drops of concentrated HCl
14 drops of thioacetamide (11%, w/v) and centrifuge (3000 rpm, 4 dk)
After heating in water bath for 5 min, decant the liquid part and wash precipitate with the washing solution
(washing solution: 2 drops of NH4Cl, 2 drops of thioacetamide and 16 drops of distilled water)
HgS, CuS, CdS, PbS, Bi2S3 As2S3, SnS, Sb2S3
20 drops of 3 M KOH
Heating in water bath for 3 min
Wash with 10 drops of 3M KOH and wash with 20 drops of distilled water
24 drops of 6 M HNO3
Heating in a water bath for 5 min
SUPERNATANT B: Pb2+, Bi+3, Cu+2, Cd+2
2 drop of 6 M H2SO4
Evaporate the solvent in a crucible.
Cool it until room temperature
Add 40 drops of distilled water and stir.
PRECIPITATE C: PbSO4
SUPERNATANT C: Bi+3, Cu+2, Cd+2
Add NH4OH until the solution is basic and then add excess 3 drops of NH4OH
SUPERNATANT D: Cu+2, Cd+2
Add drop by drop 1 M KCN until blue color disappears.
Add excess (2-3 drops) KCN
Add 6 drops of thioacetamide (11% w/v)
Heat it in a water bath for 5 min. Cd test is positive if yellowish precipiates are formed.
Cu test is positive if the supernatant C is blue.
If supernatant C is blue
If supernatant C is not blue
Heat in a water bath for 5 min. Cd test is positive if yellowish precipiates are formed.
Add 3 M HCl until the supernatant is mild acidic. Precipitates will be fomed if at least one of the analyte exist in the sample.
Discard the supernatant and keep the precipitate.
Add 20 drops of concentrated HCl.
Heat in a water bath for 5 min.
PRECIPITATE E: As2S3 ve As2S5
Wash with 10 drops of distilled water for three times.
Add 20 drops of concentrated HNO3.
Heat and stir in a water bath for 5 min
Add 10 drops of 0.5 M AgNO3 and stir.
Add 10 drops of 2.5 M sodium acetate. As3+ is positive if red-brown colored Ag3AsO4 precipitates are formed.
SUPERNATANT E: Sn+4 ve Sb+3
Divide into two parts
Add drop by drop NaOH until the solution is basic.
Add few drops of Sodium bismuthate solution. Sn+4 test is positive if black precipitates are formed after a while.
Sn+4 test
Sb+3 test
Add 6 drops of thioacetamide and heat in a water bath. Sb+3 test is positive if orange colored Sb2S3 precipitates are formed.