New conditions are described for the quantitative production of the colored compound from trichloroethylene and pyridine in the presence of alkali. A more efficient apparatus is described for the absorption of trichloroethylene steam distilled from blood. The apparatus could be used for the recovery of traces of other volatile liquid compounds. It was shown that the concn. of trichloroethylene in approx. 1 ml. blood samples can be estimated to the nearest ug. at concns. between 1 and 12 mg./100 ml.