Articles you may be interested inA computer-controlled apparatus for performing pressure-composition-temperature measurements on metal hydrides with protium, deuterium, and tritium Rev.A high precision, computer-controlled adsorption isotherm apparatus has been constructed and used to investigate a variety of physisorbed systems. Suitable for absolute measurements, this apparatus features good vapor pressure resolution and outstanding temperature stability. The hallmark of the apparatus, however, is the graphical computer interface, written using the popular LABVIEW package, which offers a flexibility and ease-of-use not achieved in previous automated systems. This article will demonstrate the quality of data obtainable with this system, as well as the simplicity of operation afforded by the graphical interface.

The wetting properties of NH 3 films on graphite have been examined over a temperature range of approximately 50 K (centered about the bulk triple point of 195.4 K) using a combination of highresolution vapor pressure isotherms and elastic neutron diffraction. Between 172 and 215 K, a single adsorption step appears at reduced pressures above 0.5. As the system is cooled, the position of this step (which is shown to be associated with the formation of a thin liquid film) increases smoothly between 0.5 and 0.95. Evidence is put forward that there is a transition from complete wetting to incomplete wetting to nonwetting. Also, the role of cluster formation and hydrogen bonding is discussed.[S0031-9007(97)03608-9]