Test for Cations

Flame Tests

Lithium - Li+, burns with a crimson-red flame.

Sodium - Na+, burns with a yellow-orange flame. 

Potassium - K+, burns with a lilac flame.

Calcium - Ca2+ burns with a brick-red flame

Precipitates (All add to sodium hydroxide)

Copper(II)- CU2+, turns blue.              Cu2+(aq) + 2OH-(aq) = Cu(OH)2(s)

Iron(II)- Fe2+, turns green                    Fe2+(aq) + 2OH-(aq) = Fe(OH)2(s)

Iron(III)- FE3+, turns reddish-brown        Fe3+(aq) + 3OH-(aq) = Fe(OH)3(s)

Ammonium ions test

Mix dilute sodium hydroxide with ammonium compound, and heat. Using a damp piece of red litmus paper, hold over the reaction. If ammonium ions are present, the red litmus paper will turn blue.