Page 73 - Chemistry - XI

2. NH CNS test:
4

CoCl +4NH CNS NH CoCNS +2NH Cl
2 4 4 2 4 4
Blue

FLOW CHART FOR ANALYSIS OF GROUP - IV

Filtrate of Group III

Pass H S
2

Precipitate No precipitate

Group IV present Group IV absent

Filter
Proceed for analysis

Precipitate of Group V and VI

White ZnS Flesh coloured MnS Black NiS or CoS
White ZnS
Dissolve in dil. HCl Dissolve in aqua regia and
and boil off H S gas. Dissolve in dil. evaporate to dryness. Add
2
Divide into two parts HCl and boil off water and divide the solution
H S
Add NaOH solution KFeCN 2 into three parts:

dropwise 4 6 Scarlet red
White ppt. soluble in Bluish white ppt. ppt. gets Add NH OH ppt.
4
excess NaOH (excess) followed
dissolved by DMG solution in

NaOH solution excess
and then Br water +2
Zn confi rmed 2 Ni confi rmed
+2
White ppt. which Yellow ppt.

turns brown or black Acidify with
on adding Br water CH COOH and add
3
2
solid KNO
+2
2 Co confi rmed
Mn confi rmed Blue
+2
colouration in
organic layer
Add 1 mL of acetone
and solid NH CNS and CNS and
4
shake it well. Co +2
Co confi rmedconfi rmedconfi rmed
Co
+2
+2
71