3-Chloro-4-amino benzene sulphonylfluoride (1 part) was stirred in acetic/propionic acid 86/14 vol/vol (15 parts) and cooled to -5° C. Nitrosyl sulphuric acid solution (1.9 parts) was added dropwise then stirred at 0°-5° C. for 2 hours. The diazo solution was then added to a stirred mixture of N-ethyl-N-benzyl aniline (2.0 parts), methanol (50 parts), sulphamic acid (0.5 parts) and sodium acetate (5 parts) with ice/water (100 parts) at 0°-5° C. After stirring under these conditions for 1 hour, the dye was filtered off and washed well with water. The damp solid was slurried in methanol (100 parts) and re-filtered. Dried at 50° C. to yield the product 4-(2-chloro-4-fluorosulphonyl phenylazo)-N-ethyl-N-benzyl aniline (1.5 parts). When applied to polyester materials from an aqueous dispersion the dye gave orange shades. λmax 483 nm
