Identifying Physical and Chemical Phenomena with Gravimetric Water Sorption Analysis

The technique of gravimetric water sorption was used to identify samples which appear to interact with water as a chemical reagent. These were distinguished from those which take up moisture purely physically. In the latter case water acts as a probe which aids the characterization of the sample surfaces and their hydration states. After identifying the features in the sorption behavior which allow this distinction to be made, we drew the following conclusions: 1. Few if any of the samples investigated interact chemically with water. 2. The demonstration of chemical interaction of a sample with water and other vapors by sorption studies alone is not always straightforward. 3. Chemical interaction of water with samples appears to be relatively rare. The major problems associated with high humidity in the production, storage and handling of samples therefore seem to be due to physical rather than chemical degradation. This revised version was published online in August 2006 with corrections to the Cover Date.