Tests for Aqueous Cations and Metal Ions

Aluminium (Al3+)

NaOH : white ppt, colourless solution

NH3(aq) : white ppt, insoluble in excess

Ammonium (NH4+)

NaOH + NH3 : ammonia produced on warning

Calcium (Ca2+)

NaOH : white ppt, insoluble in excess

NH3 : no ppt / very slight white ppt

Chromium [III] (Cr3+)

NaOH : green ppt, soluble in excess
NH3 : grey-green ppt, insoluble in excess

Copper (Cu2+)

NaOH : light blue ppt, insoluble 

NH3 : light blue ppt, soluble, dark blue sol.

Iron [II] (Fe2+)

NaOH : green ppt, insoluble

NH3 : green ppt, insoluble

Iron [III] (Fe3+)

NaOH : red-brown ppt, insoluble

NH3 : red-brown ppt, insoluble

Zinc (Zn2+)

NaOH : white ppt, soluble in excess, colourless sol.

NH3 : white ppt, soluble in excess, colourless sol.

Lithium (Li+)

Red Flame

Sodium (Na+)

Yellow Flame

Potassium (K+)

Lilac Flame

Copper [II] (Cu2+)

Blue-green Flame