\\\\( Mg(OH)_{2} \\\\) is less soluble than \\\\( MgCO_{3} \\\\). On boiling temporary hard water containing \\\\( Mg^{2+} \\\\) ions, the ppt. obtained is of \\\\( Mg(OH)_{2} \\\\) and not that of \\\\( MgCO_{3} \\\\).\\\\(MgCO_3+H_2O\\xrightarrow{\\Delta} Mg(OH)_2\\downarrow+CO_2\\\\)