subject standard character White or yellowish powder with moisture absorption acidity 5.2～6.5 moisture ≤1.5% Heavy metal 20ppm Free aromatic amine 0.1% Free iodine The toluene layer is colorless Free iodide 20ppm Solvent residue Ethanol 0.4% or less Ignition residue ≤0.1% About the material ≤3.0% N-acetylates ≤1.5% Isomer ratio E1+Z1=40.0～51.0%, E2+Z2=49.0～60.0% content 97.0～102.5%