Abstract
Air-borne acids, alkalies, and halides introduced intolerable uncertainties into the hydrolysis of phosgene to acid and chloride ion in aqueous collection media. Colorimetric detectors produced reliable results in (1) liquid reagents, (2) impregnated paper, and (3) granular solids. “Ketone” (4,4′-diethylaminobenzophenone) substituted for the diphenylamine coupling to 4-dimethylaminobenzaldehyde in Harrison's reagent in liquid systems was sensitive to 0.1 to 10 ppm of phosgene but insensitive to SO2, H2S, HCl, NO2, or Cl2. Application of Witten and Prostak's 4-(4′-nitrobenzyl) pyridine reagent to paper delivered semiquantitative results by color comparison or gas titration. Adaptation to chlorinated solvents gave sensitivity to 0.01 ppm and a unique calibration technique. A commercial granule-filled length of stain tube further extended mobile survey facilities.