Speed-of-sound-based ortho-parahydrogen measurements

The accurate determination of the ortho-parahydrogen ratio is crucial for various applications involving liquefied hydrogen. At Dresden University of Technology, a speed-of-sound-based measurement setup using a commercial binary gas analyzer was developed in recent years. Through systematic improvements, the setup now allows for very accurate measurements. Perturbations of the speed of sound measurements were reduced significantly by incorporating the gas analyzer into a small dedicated temperature chamber and by optimizing the periphery for minimal gas purity fluctuations. A cross-comparison of the measurement system with a cryostat specifically designed for the production of variable ortho-parahydrogen ratios shows good agreement between the two systems. Although not yet commonly used, speed of sound measurements for ortho-para ratio determination show great potential for several applications.