Pigment Red 57: 1 Synonyms: C. I. Pigment Red 57: 1 C. I. 15850: 1 3-Hydroxy-4-[(4-methyl-2-sulfophenyl)azo]-2 -naphthalenecarboxylic acid calcium salt (1: 1) 1. Product Name Trade Name: Fast Rubine BK-W C. I. Number: Pigment Red 57: 1 CAS Number: 5281-04-9 EU Number: 226-109-5 Chemical Family: Mono azo 2. Physical, Chemical and Fastness Properties Molecular Weight: 424.46 Molecular Formula: C18H12N2O6SCa P. H. Value: 7.0-8.0 Density: 1.7 Oil Absorption (ml/100g)%: 45-55