 Iron ( III ) chloride has a relatively low melting point and boils at around 315 ° C. The vapour consists of the dimer Fe2Cl6 ( c.f. aluminium chloride ) which increasingly dissociates into the monomeric FeCl3 ( D3h point group molecular symmetry ) at higher temperature , in competition with its reversible decomposition to give iron ( II ) chloride and chlorine gas . 
