An Absorption Dew-Point Hygrometer Using a Differential Pressure Gauge

Abstract

An absorption hygrometer, capable of measuring dew point accurately with a small amount of sample gas, is presented.
The dew-point hygrometer consists of two sample vessels of about 0.2l capacity, respectively, connected by a U-tube oil manometer. A case packed with an absorbent, such as activated alumina, is attached to the lid of one vessel. The absorbent is dropped down into the vessel and the pressure difference of the gases in the two vessels is measured. From the pressure of the initial sample gas and the pressure difference after absorption, the water vapor pressure of the sample gas is known.
The pressure difference attains eqilibrium in about 10_??_20 min after the dropping down of the absorbent. Measurements of dew point in the range of -36_??_25°C are made by using several absorbents and the results are discussed.