Mercurous Chloride or Calomel (Hg2Cl2)
Mercurous Chloride or Calomel (Hg2Cl2)
Preparation:- 1. It is obtain by adding HCl to mercurous Nitrate solution. Hg2 (NO3)2 +2HCl ? Hg2Cl2 +2HNO3 white 2. It is obtained by heating mercuric chloride with Hg. HgCl2+Hg ? Hg2Cl2 3. Commercially it is obtained by heating HgSO4 and NaCl with Hg. HgSO4 + Hg + NaCl ? Hg2Cl2 + Na2SO4 Properties:- 1. It is white amorphous solid insoluble in water. 2. When heated strongly, it decomposes forming HgCl2 and Hg. Hg2Cl2 ? HgCl2 +Hg 3. Dissolves in aqueregia, forming mercuric chloride. 3HCl + HNO3 ? NOCl + 2H2O +2Cl Hg2Cl2 + 2Cl ? 2HgCl2 Hg2Cl2 + 3Hcl +HNO3 ? 2HgCl2 + NoCl + 2H2O 4. Action of NH3:- With NH3, Hg2 gives a black ppt of mercury and mercuric amino chloride, Hg2Cl2 + NH3 ? Hg + Hg (NH2) Cl + NH4Cl Uses:-
- It is used medicine as mild purgative.
- It is used in making calomel electrode.