Test for Aqueous Cations

• Cation: Aluminum (Al3+)

  
  

  With Aqueous NaOH: White soluble precipitate, turns colorless in excess

  
  

  With aqueous ammonia: White precipitate, insoluble in excess
• Cation: Ammonium (NH4+)

  With Aqueous NaOH: Pungent ammonium gas produced turns damp red litmus blue
• Cation: Calcium (Ca2+)

  With Aqueous NaOH: White precipitate, insoluble in excess

  With aqueous ammonia: Faint or no precipitate
• Cation: Copper (Cu2+)

  With Aqueous NaOH: Blue precipitate, insoluble in excess

  With aqueous ammonia: Blue precipitate, soluble in excess to give a dark blue solution
• Cation: Iron(II) (Fe2+)

  With Aqueous NaOH: Dirty green precipitate, insoluble in excess

  With aqueous ammonia: Dirty green precipitate, soluble in excess
• Cation: Iron(III) (Fe3+)

  With Aqueous NaOH: Reddish-brown precipitate, insoluble in excess

  With aqueous ammonia: Reddish-brown precipitate, insoluble in excess
• Cation: Zinc (Zn2+)

  With Aqueous NaOH: White precipitate, soluble and turns colorless in excess

  With aqueous ammonia: White precipitate, soluble and turns colorless in excess
• Cation: Chromium (Cr3+)

  With Aqueous NaOH: Grey green precipitate, soluble to give dark green solution in excess

  With aqueous ammonia: Grey green precipitate, insoluble in excess