HIGH PRECISION DIFFERENTIAL INFRARED ANALYSIS OF GASES

Abstract

The principles of differential spectrophotometry have been applied to the analysis of gaseous mixtures with a resulting precision of 0.1 to 0.2 percent. A standard gas at a pressure calculated to give an absorbance of 1.2 at an absorption peak is placed in both cells of a double beam spectrophotometer. The optical null position is read on the chart, the reference cell closed, and the sample cell evacuated. The sample is then metered into the sample cell until the pen is nearly rebalanced. The ratio of the reference pressure to the resulting sample pressure gives the analysis directly in mole percent. The difference between observed pen position and true balance necessitates an additional correction factor which can be readily calculated. The application of this technique to mixtures containing overlapping bands is discussed. A possible adaption of these procedures to precision automatic multicomponent analysis in a gas stream also is considered.