This document discusses methods for determining hemoglobin levels. It describes hemoglobin as a protein in red blood cells that carries oxygen and transports carbon dioxide. A hemoglobin test measures the amount of hemoglobin in blood, and a low level indicates anemia. The document then outlines several colorimetric, specific gravity, gasometric, and chemical methods for measuring hemoglobin, including the cyanmethemoglobin and Drabkin's solution photoelectric methods. Interpretation of specific gravity testing and potential technical errors are also covered.