In this process hydrated lime and sodium carbonate are added to precipitate calcium and mangnesium icons as compound of law solubilit. 

Temporary hardness :   

Ca(HCO3)2+Ca(OH)2→2CaCO3↓+2H2O

Mg(HCO3)2+2Ca(OH)2→2MgCO3+2H2O

MgCO3+Ca(OH)2→Mg(OH)2+CaCO3

Permanent hardness : 

CaSO4+Na2CO3→CaCO3+Na2SO4

MgSO4+Na2CO3→MgCO3+Na2SO4

MgCO3+Ca(OH)2→Mg(OH)2+CaCO3

For above that we can see permanent hardness remove by the chemical treatment but temporary hardness is remove by both boiling and temporary treatmen.