Formalin-based fixatives with mercury, such as B5 and Zenker's, are used very little due to safety concerns, but substitutes for the mercury have made them safer to use. They are excellent fixatives for lymph nodes and bone marrow that provides brilliant nuclear details, but are NOT the best choice for IHC staining. Bouin's fixative is a formalin-based solution with picric acid (an explosive compound) and acetic acid that is NOT suggested for use with IHC staining. It is difficult to completely remove picric acid from tissue and will produce unclear and inadequate staining.
