Used in Addenbrooke's Clinical Biochemistry Department to measure carbon monoxide in blood, the gas was evolved from the patient's blood sample in one compartment, and diffused into a measurement solution of palladium chloride (which changed colour) in the other compartment. Professor Edward Conway developed his Units in Dublin in the early 1930's for a variety of analyses on small blood samples (the carbon monoxide method originated in 1948), and they continued in use until becoming obsolete in hospital labs by the early 1960's. Addenbrooke's was virtually unique in retaining a Conway Unit method in the repertoire until 1980.