 The descriptor hydrated or anhydrous is used when referring to iron ( III ) chloride , to distinguish between the two common forms . The hexahydrate is usually given as the simplified empirical formula FeCl3 ⋅ 6H2O . It may also be given as <unk> [ Fe ( H2O ) <unk> ] Cl ⋅ 2H2O and the systematic name <unk> ( III ) chloride dihydrate , which more clearly represents its structure . 
