There are more red pigments used in inks th an any other organic colour. Some of the more common are the para reds (lakes based on the azo dye from para-nitroaniline and ß-naphthol), lithol reds (e.g. Pigment Red 57: 1, a calcium salt of an azo dye, which is the most important magenta colourant in inks), rhodamine reds (e.g. Pigment Red 81, which
is rhodamine 6G laked by precipitation with phosphotungstic and phosphomolybdic acids) and Red Lake C (Pigment Red 53:1 (see IARC, 1993b), which is the barium salt of the azo dye obtained from 2-amino-4-methyl-5-chlorobenzenesulfonic acid and ßnaphthol).