Clark's method is used to remove temporary hardness of water, in which bicarbonates of calcium and magnesium are reacted with slaked lime Ca(OH)$_2$. Ca(HCO$_3$)$_2$ + Ca(OH)$_2$ $\rightarrow$ 2CaCO$_3$ $\downarrow$ + 2H$_2$O; Mg(HCO$_3$)$_2$ + 2Ca(OH)$_2$ $\rightarrow$ 2CaCO$_3$ $\downarrow$ + Mg(OH)$_2$ $\downarrow$ + 2H$_2$O