Stephan, constant

Fig. 12.3. Synthetic spectra for a region with constant star-formation rate for the ages indicated, assuming a Salpeter IMF cut-off at 75 MQ. After White (1989), based on computations by Gustavo Bruzual. With kind permission from Kluwer Academic Publishers. Courtesy Stephane Chariot.

Xenon + water. The solubility data of Potter and Clynne ((5) and of Stephan, Hatfield, Peoples and Pray (10 ) were used to estimate the mole fraction solubility at one atmosphere xenon pressure at the higher temperatures. The two sets of data were combined with the 20 solubilities selected from five papers by Battino (2) in a linear regression. Figure 6 shows the data, and Battino s equation and the three constant equation. The three constants for the tentative equation for use between the temperatures of 350 and 600 K are in Table V. The Stephan et al. solubility value at 574 K was not included in the regression. 

Hydrogen + water. Battino (4) selected 69 solu-bility values from nine papers that reported measurements between temperatures of 273 and 348 K. The mole fraction solubilities at one atmosphere partial pressure of hydrogen at the higher temperatures were estimated from the data of Wiebe and Gaddy (11), Pray, Schweichert, and Minnich (12 ), and Stephan, Hatfield, Peoples and Pray (1 ). The data from Pray, Schweichert and Minnich were combined with Battino s selected data in a linear regression to obtain the tentative four constant equation for the hydrogen solubility in water between 350 and 600 K (Figure 7 and Table V). 

Several authors have already developed methodologies for the simulation of hybrid distillation-pervaporation processes. Short-cut methods were developed by Moganti et al. [95] and Stephan et al. [96]. Due to simplifications such as the use of constant relative volatility, one-phase sidestreams, perfect mixing on feed and permeate sides of the membrane, and simple membrane transport models, the results obtained should only be considered qualitative in nature. Verhoef et al. [97] used a quantitative approach for simulation, based on simplified calculations in Aspen Plus/Excel VBA. Hommerich and Rautenbach [98] describe the design and optimization of combined pervaporation-distillation processes, incorporating a user-written routine for pervaporation into the Aspen Plus simulation software. This is an improvement over most approaches with respect to accuracy, although the membrane model itself is still quite... 

A large number of titanium complexes are known and it is not possible to review the hterature comprehensively in the space available. More comprehensive treatises have been published by Stephan, McAuhffe, and Clark. Titanium in its common oxidation states is quite labile. Water exchange is used as a convenient benchmark. The rate constant for water exchange in the Ti species [Ti(H20)6] " is 1.8 x 10 s at room temperature, and a lower limit of 3.4 x 10 s has been placed on the exchange of terminal water ligands in oligomeric hydrolyzed Ti solutions. These values can be compared to rate constants for exchange of 1.6 x 10 s for [Fe(H20)6] + and 2.4 x 10 for the famously inert [Cr(H20)6] +. ... 

---