Precipitation reaction of sodium iodide and mercury(II) chloride

Pale yellow sodium iodide solution is added to colorless mercury(II) chloride solution.

Approximately 2 mL of Solution A (on the left) is added to a sample of Solution B (on the right) with a dropping pipet. If a precipitate forms, the resulting precipitate is suspended in the mixture. The mixture is then stirred with a glass stirring rod and the precipitate is allowed to settle for about a minute.

Solution A: 0.5 M sodium iodide, very pale yellow
Solution B: 0.1 M mercury(II) chloride, colorless
Precipitate: orange
HgCl2(aq) + 2 NaI(aq) —> HgI22(s) + 2 NaCl(aq)

Credits: 
  • Design
    • Kenneth R. Magnell Central Michigan University, Mt. Pleasant, MI 48859
    • John W. Moore University of Wisconsin - Madison, Madison, WI 53706
  • Video
    • Jerrold J. Jacobsen University of Wisconsin - Madison, Madison, WI 53706
  • Text
    • Kenneth R. Magnell Central Michigan University, Mt. Pleasant, MI 48859