2 A metal in equilibrium with a saturated solution of a slightly soluble salt (Class Electrodes) Ag AgCl Cl, (a-1) AgCl()+e+Ag Cl (6r-7) Reference electrodes Saturated calomel electrode (SCE) Hg Hg2Cl2(s)I,; (sat'd KCL) Hg2Cl2(s)+ 2e+ 2Hg 2CI(sat'd KCL)(6r-8)2) A metal in equilibrium with a saturated solution of a slightly soluble salt (Class Ⅱelectrodes) AgAgCl Cl - ,(=1) AgCl(s) + e￾Ag + Cl – Reference electrodes Saturated calomel electrode (SCE) HgHg2Cl2(s)Cl - ,(sat’d KCL) Hg2Cl2(s) + 2e- 2Hg + 2Cl – (sat’d KCL) (6r-7) (6r-8)