Eosin Y (yellowish) (C.I. 45380) 1 Product Result. | Match Criteria: Keyword. Synonym: Eosin Y (yellowish) (C.I. 45380) Empirical Formula (Hill Notation): C20H6Br4Na2O5. Molecular Weight: 691.85. CAS Number: 17372-87-1. 1.15935. for microscopy Certistain ®.