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What are you testing the solution for?
How would you test a solution containing only Co2+ and Fe3+ ions?
3 answers
Group III cations
Fe^3+ is in group IIIA (the iron group of group III) and Co^2+ is in group IIIB (the Zn group of group III).
Group IIIA is pptd with NH3 in an NH4Cl solution. I would confirm Fe^3+ by dissolving a small amount of the Fe(OH)3 in HNO3 and adding KCNS. A deep red color due to FeCNS^2+ confirms iron(III).
To the solution from which iron was removed, saturate with H2S to ppt CoS. Dissolve the CoS in a little HNO3, add NaOH. A blue ppt of Co(OH)NO3 that turns pink due to the presence of Co(OH)2 confirms Co(II).
Group IIIA is pptd with NH3 in an NH4Cl solution. I would confirm Fe^3+ by dissolving a small amount of the Fe(OH)3 in HNO3 and adding KCNS. A deep red color due to FeCNS^2+ confirms iron(III).
To the solution from which iron was removed, saturate with H2S to ppt CoS. Dissolve the CoS in a little HNO3, add NaOH. A blue ppt of Co(OH)NO3 that turns pink due to the presence of Co(OH)2 confirms Co(II).
1 answer