An Experimentally Simple Method for Measuring Sorption Isotherms

Abstract

We describe a simple, yet practical and precise, way of measuring sorption isotherms with each sample in its own glass jar with a saturated salt solution. The measurements are done with below-balance weighing and with the sample kept inside the closed jar during the whole measurement period, providing constant relative humidity (RH) conditions. The technique has been tested on microcrystalline cellulose and bentonite clay. The agreement with literature values was good; the differences seen for bentonite at high RH are discussed in terms of the slow attainment of equilibrium for this material.

Keywords:

• Sorption isotherm
• Measurement method
• Saturated salt solutions
• Glass jar

Acknowledgments

We thank Bengt Nilsson and Natalia Markova for their help with previous versions of this method. This research was funded by FORMAS (LW, KS) and the Swedish Nuclear Fuel and Waste Management Company (AD).