Determination of water in hydrogen chloride gas by a condensation technique

The determination of trace amounts of water in gaseous hydrogen chloride has been of considerable interest to manufacturers of semiconductor materials. Many different methods have been postulated in the detection of water in hydrogen chloride, including Karl Fischer titrations, infrared spectrometric techniques, and gravimetric procedures using desiccants. Despite varying degrees of success at high-moisture concentration ranges, 1000 ppm (v/v) and up, these methods become tedious and unreliable for measuring water in hydrogen chloride in the 1-1000 ppm range. We have found a method for moisture in hydrogen chloride, analogous to dew point determinations used for inert gases, that is rapid and reproducible. A calibration curve of parts per million (v/v) water in hydrogen chloride vs. condensation temperature was constructed by dynamically blending a low part per million moisture balance nitrogen standard with dried hydrogen chloride gas. In addition, variation of the condensation temperature was monitored as the dried hydrogen chloride was diluted with dried gaseous nitrogen.