A lab. expt. for the qual. and quant. anal. of carbon monoxide in blood, used by forensic chemists and toxicologists, is presented. The expt. is designed for first-year general chem. students. The presence of CO in blood was detected by the Conway diffusion method, where the sulfuric acid is used to release carbon monoxide from the Hb mols. The CO then diffuses to a soln. of palladium chloride and reduces the Pd2+ ions to metallic Pd, which appears as a palladium mirror on the surface of the PdCl2 soln. The concn. of CO in blood was detd. by measuring the concn. of carboxyHb by visible spectroscopy, converting the oxyHb to reduced Hb, and measuring the concn. of Hb by visible spectroscopy.