Low resolution (20 cm −1) transmission measurements were obtained for strong infrared absorption features of CO, HCI, and SO 2. Experiments were performed at room temperature with a Perkin-Elmer 621 grating spectrophotometer and a 10 cm pathlength cell having CsI windows. Some 4 meter CO studies were also made. The absorbers were placed in a carrier gas of nitrogen or carbon dioxide, and the partial pressures of absorber and diluent, respectively, were varied. The logarithm of the absorbance was represented as having a power law dependence on absorber amount and total pressure, where typically each variable varied over a larger range than an order of magnetude. The CO spectrum was synthesized theoretically and compared with the power law representation to explore the latter's range of validity. Finally, it was concluded that none of the above gases are significant for the strong greenhouse effect on Venus, either because they are not present in sufficient amounts, or because they produce opacity in spectral regions where carbon dioxide is already quite opaque.