Many new applications for water as a solvent at pressures P > Psat and
elevated temperatures loom on the horizon. In this brief review I describe a few of these new applications, ordered as a function of increasing solvent temperature. At 190 - 220°C hot liquid water is able to dissolve all the hemicellulose and much of the lignin from whole biomass feeds, thus potentially leading to the development of a chemical free pulping technology. In water above 225°C tert-hutanol spontaneously eliminates water to form isobutene. Even in the absence of acid-catalysts this reaction is fast: equilibrium is established in less than one minute. At somewhat higher temperatures (320 - 385°C), both secondary and primary alcohols quickly eliminate water in the presence of trace amounts of acid to form the corresponding alkene. Studies of the influence of pressure on the acid-catalyzed rate of 1-propanol dehydration in water near its critical point indicate no unexpected or abnormal behavior. At still higher temperatures (600°C) in the presence of a proprietary catalyst, organic materials (such as sewage sludge and, the model compound glucose) can he completely gasified in supercritical water to a hydrogen rich synthesis gas. High weight hourly space velocities are realized, and the water exits the reactor with virtually no organic contamination. The gaseous product is available at 34.5 MPa (5000 psi) and is a potential source of pure, storable hydrogen for fuel cell applications.