2.1 chemicals
the chemicals, FeCl3.6H2O, ethylene glycol, CH3COONa.3H2O, were A.R. grade and used as received. the phosphate aqueous solution was prepared by dissolvting certain amount of KH2PO4 into deionzed water. An appropriate volume of 0.1 mol/L HNO3 and NaOH solutions were used to adjust the pH phosphate solution