A TECHNIQUE FOR THE DETERMINATION OF WATER IN AIR AT TEMPERATURES BELOW FREEZING

Abstract

An investigation of ice fog in Alaska required a technique for the determination of the water content of the atmosphere at temperatures between ?20 to ?55C. No satisfactory method for direct field measurements at these low temperatures was available. A field sampling-technique was developed which consisted of extracting the contained water by bubbling the air through absolute methanol, an aliquot of which was then titrated with Karl Fischer reagent. A visual end-point was applicable. The method permitted rapid titration, required simple apparatus, and measured the amount of moisture in the air directly to within 2 per cent of the absolute values. A method of filtering the air in order to separate water vapor from precipitated water was also developed for sub-freezing temperatures. Humidity observations were extended to levels above the surface by drawing a known volume of air into the bubbler through polyethylene tubing supported by captive balloons. Results obtained with these techniques are included in a discussion of humidities determined at Eielson Air Force Base, Alaska, during the winter of 1952?1953.