GROUP 2
CATION
Nurhasni, M.Si
Adawiah, S.Si
Cationic Solutions
Group I Insoluble chlorides: Ag+, Hg22+, Pb2+
Group II Insoluble sulfides in acidic medium : Hg2+, Cu2+,
Pb2+, Bi3+, Cd2+, As3+, Sb3+, Sn4+ (metallic sulfide precipitates
with smaller Ksp)
Group III Insoluble sulfides or hydroxide in alkalin medium :
Al3+, Fe3+, Fe2+, Co2+, Ni2+, Cr3+, Zn2+, Mn2+ (metallic sulfide
precipitates with greater Ksp)
Group IV Insoluble Carbonate : Ba2+, Mg2+, Ca2+, Sr2+
Group V Soluble Cation : K+, NH4+, Na+
Group II Insoluble sulfides in acidic medium
Copper subgroup
HgS, CuS, PbS, Bi2S3, CdS
Arsenic Subgroup
As2S3, Sb2S3, SnS2
Insoluble in KOH and
soluble only in Nitric
acid (HNO3)
Soluble in KOH and Nitric
acid (HNO3)
Flow Chart for Separating Copper and Arseic Group
Cationic solution
Cu2+, Bi3+, Sb3+, Sn4+
pH 0,5
Tioacetamide 13%, Δ, centrifuge and separate
(Repeat 13% TA precipitation once)
Precipitate
Bi2S3, CuS, Sb2S3, SnS2
Solution
Wash ppt with NH4Cl 6M and water, centrifuge
Add KOH 0,5M to precipitate and mix well
Heat in boiling water bath
centrifuge and separate the precipitate and supernatant
(Repeat this extraction with KOH once)
Precipitate of Copper group (2A)
Bi2S3, CuS
Solution of arsenic group (2B)
SbS33-, SbO33-, SnS32-, SnS2OH-, (KOH)
Flow Chart for Separating Cu2+ and Bi3+
Precipitate of
Bi2S3, CuS,
Wash ppt with NH4NO3 and water, centrifuge
Add HNO3 6M and water, Heat in boiling water bath
centrifuge to obtain the solution
Solution of Cu2+, Bi3+
Discard residue
(contains S precipitate and NO2 gass)
Add and mix with NH3 15M until basic (confirm with litmus test)
centrifuge and separate the precipitate and supernatant
2Bi(OH)3(aq) + 3Sn(OH)3-(aq) + 3OH-(aq) ⇌ 2Bi↓ + 3Sn(OH)62-(aq)
Black ppt
of Bi
Add sodium
stanite reagent
(Sn(OH)3-
Whtie Precipitate of
Bi(OH)3
The deep blue solution of Cu(NH3)42+
Flow Chart for Separating Sb3+ and Sn4+
Identification of
Group 2A cation
2+
Cd Cation
Add H2S gass
Yellow Precipitate
of CdS
Concentrate
acid
Solution
conatins Cd2+
Add NaOH
excess
Whtie Precipitate
of
Add NH4OH
Whtie Precipitate
of
Add acid
soltion
Solution conatins
Cd2+
Add NH4OH
excess
Solution conatins Cd2+
2+
Cu Cation
Add H2S gass, H+
pH 0,5
Black Precipitate
of CuS
Add NaOH, 0°C
excess
Blue Precipitate
of
White Precipitate
of with brown
solution
Heat in boiling
water bath
HNO3
Solution
conatins Cu2+
Add KI
White ppt of
S (sulfur)
Black ppt of
Add
NH4OH
Blue precipitate
Add NH4OH
excess
Blue Solution
conatins Cu2+
Add
K4Fe(CN)6, H+
Reddish Brown
Precipitate of
Cu2[Fe(CN)6]
Bi3+ Cation
Add H2S gass, H+
pH 0,5
White Precipitate
of Bi(OH)3
Black Precipitate
of HgS
Add concentrate
HNO3
Solution
contains Bi3+
White ppt of
S (sulfur)
Add
NH4OH
Add KI
Add NaOH
Black Precipitate
of
Add NaOH excess
Slightly soluble
of Bi3+
White
precipitate
Add NaOH excess
Orange colour
complex of [BiI4] -
2+
Hg Cation
Add H2S gass, H+
pH 0,5
Black Precipitate
of HgS
Add HCl and
HNO3
Solution
contains Hg2+
Add NaOH, 0°C
excess
Add KI
Red Precipitate of
KI excess
Solution
contains
Reddish Brown
Precipitate of
Add
NH4OH
White
precipitate
Add SnCl2
White precipitate
of
Add NH4OH
excess
Grey precipitate
THANKS!
Any questions?
You can find me at: adawiah@uinjkt.ac.id