Which chemical is used specifically for staining hemoglobin?

Benzidine is a chemical specifically used for staining hemoglobin due to its ability to form a complex with the heme portion of hemoglobin, resulting in a color change that can be visualized under a microscope. This reaction allows for the identification of erythrocytes or areas of hemorrhage in tissue samples. The specificity of benzidine for hemoglobin makes it a valuable tool in histopathology for detecting blood and assessing tissue sections for hematological conditions.

In contrast, rhodamine B is a fluorescent dye used for general staining of proteins and does not have a particular affinity for hemoglobin. Methyl green is primarily used for nucleic acid staining, particularly DNA, and does not interact specifically with hemoglobin. Feulgen stain is specifically designed to identify DNA, making it unsuited for detecting hemoglobin. Thus, benzidine stands out as the most appropriate choice for this specific task.