Field Stain B has been formulated to be used on thick blood smears that are required for detection of malarial parasites in blood sample. It contains eosin Y with precise volume of buffer having chemical formula C20H6Br4Na2O5 and molar mass of 647.890 g/mol. This is a red colored acidic stain which provides color to cytoplasm. It is highly appreciated for having ability to effectively define morphology of various spirochaetes, parasites, and protozoa. Field Stain B contains eosin, disodium hydrogen phosphate, and potassium dihydrogen phosphate. It must be kept under dark as it is sensitive from bright light.