Metallic ions can be classified as colourless and coloured ions.
Colourless metallic ions
The most commonly used colourless ions are zinc (Zn2+), calcium (Ca2+) Aluminum (AL3+) lead (Pb2+)
| Test | Observation | Inference |
| Unknown solution +NaOH
in drop(aq) In excess |
White precipitates formed. | Zn2+ AL3+ Ca2+ Pb2+ present |
| White precipitates dissolves | Zn2+ AL3+ Pb2+ present | |
| Unknown solution +NaOH
in drop(aq) In excess |
White precipitates formed. | Zn2+ AL3+ Pb22+ present |
| White precipitates dissolves | Zn2+ is confirmed. |
NB – Ca2+ remains insoluble in excess of NaOH(aq) and does not react with NH3(aq)
Also, AL3+ and Pb2+ are insoluble in excess NH3(aq) but Zn2+ dissolve in excess of NH3(aq)
Coloured Metallic ions
Iron has two ions, which are Fe3+ and Fe2+ Copper (Cu2+) ions
| Reading | Ions | Observation |
| NaOH(ag) | Fe2+ | Dirty green gelatinous precipitate which remain insoluble in excess of NaOH(aq) |
| Fe3+ | Reddish – brown gelatinous precipitate which remains insoluble in excess of NaOH(aq) | |
| Cu2+ | Blue gelatinous precipitate is formed, which is insoluble in excess of NaOH(aq) | |
| NH3(ag) | Fe2+ | Dirty green gelatinous precipitate which remain insoluble in excess NH3(ag) |
| Fe3+ | Reddish – brown gelatinous precipitate which remains insoluble in excess | |
| Cu2+ | Blue gelatinous precipitate is formed, which is insoluble in excess of aqueous ammonia to deep blue solution. (confirmatory test) | |
| Potassium | Fe3+ | Light blue precipitate |
| Hexacyano-
Ferrate (II) |
Fe3+ | Deep blue precipitate |
| Potassium | Fe2+ | Deep blue precipitate |
| Hexacyano-
Ferrate (III) |
Fe3+ | Brown colouration |
| Potassium | Fe2+ | No action |
| Thiocyanate
Solution |
Fe3+ | Blood-red colouration |
NB- Copper salt has a bluish-green colour when viewed on a non-luminous flame.