Vapor origin

Rhombohedral BN (rBN) forms in the fusion product of KCN and Na2B407 and by deposition at 1500°C from hexagonal BN vapor originally formed at 2100°C in a graphite resistance tube furnace. Products collect on a pitted carbon film. ... 

Referring to Figure 11.28, describe all the phase changes that would occur in each of the following cases (a) Water vapor originally at 0.005 atm and —0.5 °C is slowly compressed at constant temperature until the final pressure is 20 atm. (b) Water originally at 100.0 °C and 0.50 atm is cooled at constant pressure until the temperature is —10 °C. 

To meet present requirements for nitrogen gas at pressures up to 13,500 psi, studies revealed the most practical and economical system to be an immersed, reciprocating liquid nitrogen pump and vaporizer. Originally, Linde pumps of this type were designed for pressures of only about 3500 psi. 

A sample of 1.000 mol of water vapor originally at 500.0 K and a volume of 10.0 L is expanded reversibly and adiabatically to a volume of 20.0 L. Assume that the water vapor obeys the van der Waals equation of state and that its heat capacity at constant volume is described by... 

Figure 15 shows results for a difficult type I system methanol-n-heptane-benzene. In this example, the two-phase region is extremely small. The dashed line (a) shows predictions using the original UNIQUAC equation with q = q. This form of the UNIQUAC equation does not adequately fit the binary vapor-liquid equilibrium data for the methanol-benzene system and therefore the ternary predictions are grossly in error. The ternary prediction is much improved with the modified UNIQUAC equation (b) since this equation fits the methanol-benzene system much better. Further improvement (c) is obtained when a few ternary data are used to fix the binary parameters. 

At low temperatures, using the original function/(T ) could lead to greater error. In Tables 4.11 and 4.12, the results obtained by the Soave method are compared with fitted curves published by the DIPPR for hexane and hexadecane. Note that the differences are less than 5% between the normal boiling point and the critical point but that they are greater at low temperature. The original form of the Soave equation should be used with caution when the vapor pressure of the components is less than 0.1 bar. In these conditions, it leads to underestimating the values for equilibrium coefficients for these components. 

There are two approaches to explain physical mechanism of the phenomenon. The first model is based on the existence of the difference between the saturated vapor pressures above two menisci in dead-end capillary. It results in the evaporation of a liquid from the meniscus of smaller curvature ( classical capillary imbibition) and the condensation of its vapor upon the meniscus of larger curvature originally existed due to capillary condensation. 

At first we tried to explain the phenomenon on the base of the existence of the difference between the saturated vapor pressures above two menisci in dead-end capillary [12]. It results in the evaporation of a liquid from the meniscus of smaller curvature ( classical capillary imbibition) and the condensation of its vapor upon the meniscus of larger curvature originally existed due to capillary condensation. We worked out the mathematical description of both gas-vapor diffusion and evaporation-condensation processes in cone s channel. Solving the system of differential equations for evaporation-condensation processes, we ve derived the formula for the dependence of top s (or inner) liquid column growth on time. But the calculated curves for the kinetics of inner column s length are 1-2 orders of magnitude smaller than the experimental ones [12]. 

The reports were that water condensed from the vapor phase into 10-100-/im quartz or pyrex capillaries had physical properties distinctly different from those of bulk liquid water. Confirmations came from a variety of laboratories around the world (see the August 1971 issue of Journal of Colloid Interface Science), and it was proposed that a new phase of water had been found many called this water polywater rather than the original Deijaguin term, anomalous water. There were confirming theoretical calculations (see Refs. 121, 122) Eventually, however, it was determined that the micro-amoimts of water that could be isolated from small capillaries was always contaminated by salts and other impurities leached from the walls. The nonexistence of anomalous or poly water as a new, pure phase of water was acknowledged in 1974 by Deijaguin and co-workers [123]. There is a mass of fascinating anecdotal history omitted here for lack of space but told very well by Frank [124]. 

It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process). 

Eventually, not only neutral solvent molecules but also ions start to desorb from the surface of each droplet, Ions, residual droplets, and vapor formed by electrospray are extracted through a small hole into two evaporation chambers (evacuated) via a nozzle and a skimmer, passing from there into the analyzer of the mass spectrometer, where a mass spectrum of the original sample is obtained. 

The amount and physical character of the char from rigid urethane foams is found to be affected by the retardant (20—23) (see Foams Urethane polymers). The presence of a phosphoms-containing flame retardant causes a rigid urethane foam to form a more coherent char, possibly serving as a physical barrier to the combustion process. There is evidence that a substantial fraction of the phosphoms may be retained in the char. Chars from phenohc resins (qv) were shown to be much better barriers to pyrolysate vapors and air when ammonium phosphate was present in the original resin (24). This barrier action may at least partly explain the inhibition of glowing combustion of char by phosphoms compounds. 

Ref. 87. Test method ASTM E96-35T (at vapor pressure for 25.4 p.m film thickness). Values are averages only and not for specification purposes. Original data converted to SI units using vapor pressure data from Ref. 90. 

Original data converted to SI units using vapor pressure data from Ref. 72. "At20°C. 

BiaxiaHy orieated PPS film is transpareat and nearly colorless. It has low permeability to water vapor, carbon dioxide, and oxygen. PPS film has a low coefficient of hygroscopic expansion and a low dissipation factor, making it a candidate material for information storage devices and for thin-film capacitors. Chemical and thermal stability of PPS film derives from inherent resia properties. PPS films exposed to tolueae or chloroform for 8 weeks retaia 75% of theh original streagth. The UL temperature iadex rating of PPS film is 160°C for mechanical appHcatioas and 180°C for electrical appHcations. Table 9 summarizes the properties of PPS film. 

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as Hquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many Hquids in real time (14). 

Batch Stirred Tank SO Sulfonation Processes. If the color of the derived sulfonate is not critical, such as ia the productioa of oil-soluble ag-emulsifiers, a simple batch sulfoaatioa procedure can be employed based on vaporizing liquid SO (Niaol Labs, 1952) (13,263). Pilot Chemical Company adapted the original Morrisroe 60—70% oleum—SO2 solvent sulfonation process (256) to utilize 92% Hquid SO —8% Hquid SO2 mixtures, and more recently usiag 100% Hquid SO. This cold sulfoaatioa low viscosity sulfoaatioa process produces exceUeat quaHty products, and reportedly has also been adapted for continuous processiag as weU. The derived sulfonic acid must be stripped of SO2 solvent after completing sulfonation and digestion. 

---