Mercury halides
Mercury forms halides in the two oxidation states, +1 and +2. 1. Mercury(1)Chloride(Hg2Cl2) Mercury(1) chloride or mercurous chloride is known as calomel. Preparation Mercury(1)chloride is prepared by heating a mixture of mecury(2)chloride and mercury in iron vessel. HgCl2 + Hg -------> Hg2Cl2 It can also be obtained by reduction of mercury(2)chloride by reducing agents like tin(2)chloride in limited quantity. 2HgCl2 + SnCl2 --------> HgCl2 + SnCl4 Properties When heated, mercury(1)chloride decomposes into mercury(2)chloride and mercury. Hg2Cl2 -------> HgCl2 + Hg The action of aqueous ammonia on the solid mercury(1)chloride gives a mixture of black finely divided mercury and white mercury amino chloride. This reaction is an example of disproportion reaction. Hg2Cl2 + 2Nh3 -------> Hg(NH2)Cl + Hg + NH4Cl Uses of mercury(1)chloride Calomel is used in making standard calomel electrodes used as secondary reference electrode. It is also used as a purgative in medicines. 2. Merc...