A simple, accurate photoelectric method is described for the determination of oxyhemoglobin (HbO₂), methemoglobin (MHb), and sulfhemoglobin (SHb) in a single 0.1 cc blood sample. The method involves measuring the optical density of blood samples using a photoelectric colorimeter with specific filters. Methemoglobin is determined by converting it to cyanmethemoglobin (MHbCN) with sodium cyanide, and measuring the change in optical density. Sulfhemoglobin is determined by measuring the residual optical density after converting MHb to MHbCN. Oxyhemoglobin is calculated by subtracting the concentrations of MHb and SHb from the total hemoglobin concentration. The method is accurate, with errors not exceeding 0.2 gm per 100 cc for MHb and 0.1 gm per 100 cc for SHb. The method is not affected by other pigments that absorb light at 635 mμ or 620 mμ, as long as their absorption is not altered by cyanide. The method is specific for human blood and can be used in clinical investigations. The results show that the method is reliable, with a high degree of reproducibility. The method is recommended for use in determining MHb and SHb in blood samples, as it provides accurate and reliable results. The method is also useful in diagnosing conditions such as sulfhemoglobinemia and methemoglobinemia. The method is based on the principles of spectrophotometry and is applicable to various types of photoelectric colorimeters. The method is described in detail, including the reagents, procedure, and equations used for calculation. The method is suitable for use in clinical and research settings. The method is accurate and reliable, with a high degree of specificity. The method is recommended for use in clinical practice.A simple, accurate photoelectric method is described for the determination of oxyhemoglobin (HbO₂), methemoglobin (MHb), and sulfhemoglobin (SHb) in a single 0.1 cc blood sample. The method involves measuring the optical density of blood samples using a photoelectric colorimeter with specific filters. Methemoglobin is determined by converting it to cyanmethemoglobin (MHbCN) with sodium cyanide, and measuring the change in optical density. Sulfhemoglobin is determined by measuring the residual optical density after converting MHb to MHbCN. Oxyhemoglobin is calculated by subtracting the concentrations of MHb and SHb from the total hemoglobin concentration. The method is accurate, with errors not exceeding 0.2 gm per 100 cc for MHb and 0.1 gm per 100 cc for SHb. The method is not affected by other pigments that absorb light at 635 mμ or 620 mμ, as long as their absorption is not altered by cyanide. The method is specific for human blood and can be used in clinical investigations. The results show that the method is reliable, with a high degree of reproducibility. The method is recommended for use in determining MHb and SHb in blood samples, as it provides accurate and reliable results. The method is also useful in diagnosing conditions such as sulfhemoglobinemia and methemoglobinemia. The method is based on the principles of spectrophotometry and is applicable to various types of photoelectric colorimeters. The method is described in detail, including the reagents, procedure, and equations used for calculation. The method is suitable for use in clinical and research settings. The method is accurate and reliable, with a high degree of specificity. The method is recommended for use in clinical practice.