FC-401(perfluorobutanesulfonyl fluoride) Structural formula : CF3CF2CF2CF2SO2F Molecular formula: C4F10SO2 CAS No. 375-75-4 Content: 95%(min.) Appearance: colorless to yellowish liquid Density: 1.700-1.7500 Refractive index(nD25): 1.2810 Boiling point: 65-66癈 PH value: 3.8-4.8 Package: 2?kg per plastic barrel in carton Storage and shipment: general chemicals Application: As similar to perfluorooctanesulfnyl fluoride in the structure, it is used to synthesize various fluoro-containing surfactants. For example, potassium salt of perfluorobutanesulfonate is an excellent anion surfactant, and used as the best fire retardant for polycarbonate materials.