Test for positive ions

Test for positive ions

1. Flame Test

   • Metal Ions produce colours when put into a flame
     • Lithium (Li+) : Crimson
     • Sodium (Na+) : Yellow
     • Potassium (K+) : Lilac
     • Calcium (Ca2+) : Red
     • Barium (Ba2+) : Green

2. Sodium Hydroxide Solution

   • The hydroxides of most metals that have ions with 2+ or 3+ charges are insoluble in water
     • When sodium hydroxide solution is added to solutions of theses ions a precipitate of the metal hydroxide forms
       • Aluminium, calcium and magnesium ions form white precipitate.
       • When excess sodium hydroxide solution is added the precipitate of aluminium hydroxide dissolves.
       • Copper (II) hydroxide : blue
       • Iron (II) hydroxide : green
       • Iron (III) hydroxide : Brown