Vapor phase, saturated

SANDWICH CHAMBER (S-CHAMBER). A developing chamber formed from the plate itself, a spacer, and a layered or nonlayered cover plate that stands in a trough containing the mobile phase, or some other type of small-volume chamber in which vapor-phase saturation occurs quickly. 

Two additional illustrations are given in Figures 6 and 7 which show fugacity coefficients for two binary systems along the vapor-liquid saturation curve at a total pressure of 1 atm. These results are based on the chemical theory of vapor-phase imperfection and on experimental vapor-liquid equilibrium data for the binary systems. In the system formic acid (1) - acetic acid (2), <() (for y = 1) is lower than formic acid at 100.5°C has a stronger tendency to dimerize than does acetic acid at 118.2°C. Since strong dimerization occurs between all three possible pairs, (fij and not... 

Adsorption may occur from the vapor phase rather than from the solution phase. Thus Fig. Ill-16 shows the surface tension lowering when water was exposed for various hydrocarbon vapors is the saturation pressure, that is, the vapor pressure of the pure liquid hydrocarbon. The activity of the hydrocarbon is given by its vapor pressure, and the Gibbs equation takes the form... 

Frequently, vapor-phase supersaturation is studied not by varying the vapor pressure P directly but rather by cooling the vapor and thus changing If To is the temperature at which the saturation pressure is equal to the actual pressure P, then at any temperature T, Pjf = x is given by... 

Aldehydes —CHO (See also Table 7.49 for C—H.) All values given below are lowered in liquid-film or solid-state spectra by about 10-20 cm Vapor-phase spectra have values raised about 20 cm Saturated 1740-1720 ... 

Reactions with Ammonia and Amines. Acetaldehyde readily adds ammonia to form acetaldehyde—ammonia. Diethyl amine [109-87-7] is obtained when acetaldehyde is added to a saturated aqueous or alcohoHc solution of ammonia and the mixture is heated to 50—75°C in the presence of a nickel catalyst and hydrogen at 1.2 MPa (12 atm). Pyridine [110-86-1] and pyridine derivatives are made from paraldehyde and aqueous ammonia in the presence of a catalyst at elevated temperatures (62) acetaldehyde may also be used but the yields of pyridine are generally lower than when paraldehyde is the starting material. The vapor-phase reaction of formaldehyde, acetaldehyde, and ammonia at 360°C over oxide catalyst was studied a 49% yield of pyridine and picolines was obtained using an activated siHca—alumina catalyst (63). Brown polymers result when acetaldehyde reacts with ammonia or amines at a pH of 6—7 and temperature of 3—25°C (64). Primary amines and acetaldehyde condense to give Schiff bases CH2CH=NR. The Schiff base reverts to the starting materials in the presence of acids. 

The most convenient mathematical method of describing pervaporation is to divide the overall separation processes into two steps, as shown in Figure 40. The first is evaporation of the feed Hquid to form a (hypothetical) saturated vapor phase on the feed side of the membrane. The second is permeation of this vapor through the membrane to the low pressure permeate side of the membrane. Although no evaporation actually takes place on the feed side of the membrane during pervaporation, this approach is mathematically simple and is thermodynamically completely equivalent to the physical process. The evaporation step from the feed hquid to the saturated vapor phase produces a separation, which can be defined (eq. 13) as the ratio of... 

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

Determination of the Gas-Phase Temperature. The development given above is in terms of interface conditions, bulk Hquid temperature, and bulk gas enthalpy. Often the temperature of the vapor phase is important to the designer, either as one of the variables specified or as an important indicator of fogging conditions in the column. Such a condition would occur if the gas temperature equaled the saturation temperature, that is, the interface temperature. When fogging does occur, the column can no longer be expected to operate according to the relations presented herein but is basically out of control. 

Density. The density of saturated water and steam is shown in Figure 2 as a function of temperature on the saturation line. As the temperature approaches the critical point, the densities of the Hquid and vapor phase approach each other. This fact is cmcial to boiler constmction and steam purity because the efficiency of separation of water from steam depends on the density difference. 

Because calcium chloride has a number of hydrates, the one that is in equiUbrium with a saturated solution is a function of the temperature. In this case, the sohd is dissolved as it absorbs water to form the saturated solution, and three phases are present soHd, saturated solution, and vapor. Systems having these three phases, or two soHds and a vapor phase, have a constant vapor pressure at a given temperature. Therefore, Class 2 drying agents can be used to maintain a constant relative humidity. 

Fig. 1. Vapor pressure and relative humidity over CaCl solutions and solids. The straight horizontal lines ia the right-hand portion represent two soHd phases and a gas phase for vertical line iatersections. In addition, a soHd phase, saturated solution, and a vapor phase occur ia the regions between the vertical lines. The lower left-hand corner shows the ice solution line. The region ia between, with skewed isothermal lines, represents unsaturated solutions ...

When liquid content of the feed is high, a condenser and a separator are needed. The liquid-to-gas ratio can be as high, so that even at reaction temperatures a liquid phase is present. The reactor still performs as a CSTR, however the response time for changes will be much longer than for vapor phase alone. Much lower RPM will be needed for liquid-phase studies (or liquid and gas phase experiments) since the density of the pumped fluid is an order-of-magnitude greater than for vapor phase alone. In this case a foamy mixture or a liquid saturated with gas is recirculated. 

Johnson, P.C., R.C. Lemon and J.M. Berty, Selective Non-Catalytic, Vapor-Phase Oxiation of Saturated Aliphatic Hydrocarbons to Olefin Oxides, 1964, US Patent 3,132,156. 

There is no other facet where thin-layer chromatography reveals its paper-chromatographic ancestry more clearly than in the question of development chambers (Fig. 56). Scaled-down paper-chromatographic chambers are still used for development to this day. From the beginning these possessed a vapor space, to allow an equilibration of the whole system for partition-chromatographic separations. The organic mobile phase was placed in the upper trough after the internal space of the chamber and, hence, the paper had been saturated, via the vapor phase, with the hydrophilic lower phase on the base of the chamber. 

For example, for steam (saturated vapor, no liquid) distillation with one organic compound (liquid), there are two phases, two components, and two degrees of freedom. These degrees of freedom that can be set for the system could be (1) temperature and (2) pressure or (1) temperature and/or (2) concentration of the s) stem components, or either (1) pressure and (2) concentration. In steam distillation steam may be developed from water present, so there would be both a liquid water and a vapor phase water (steam) present. For such a case, the degrees of freedom are F = 2 + 2- 3 = l. 

By neglecting the specific molar volume of the saturated liquid W in relation to that of the saturated vapor V, and by assuming the vapor phase to behave as an ideal gas, i.e., P V = RT, the above equation may be arranged into... 

Thermodynamic consistency tests for binary vapor-liquid equilibria at low pressures have been described by many authors a good discussion is given in the monograph by Van Ness (VI). Extension of these methods to isothermal high-pressure equilibria presents two difficulties first, it is necessary to have experimental data for the density of the liquid mixture along the saturation line, and second, since the ideal gas law is not valid, it is necessary to calculate vapor-phase fugacity coefficients either from volumetric data for... 

After extraction of the neutral oil from the AOS sample, the neutral oil is made up volumetrically to at least a 10% solution in hexane. Of this solution 4 pi is spotted onto a silica gel TLC plate, together with terminal 5-sultone standard in the range 0.4-4 pg (equivalent to 0.1-1% sultone in the neutral oil). It is twice developed in a chamber saturated with 2-propyl ether. The solvent is completely evaporated and the spots visualized by vapor phase sulfuric acid charring using the technique described by Martin and Allen [139]. Humidity is not critical (10-30% is optimum) and activation of the plates has not been found necessary, but it might be required under conditions of high humidity. The level of sultone can be estimated by visual comparison with the standards or by the use of a densitomer. 

In this table the parameters are defined as follows Bo is the boiling number, d i is the hydraulic diameter, / is the friction factor, h is the local heat transfer coefficient, k is the thermal conductivity, Nu is the Nusselt number, Pr is the Prandtl number, q is the heat flux, v is the specific volume, X is the Martinelli parameter, Xvt is the Martinelli parameter for laminar liquid-turbulent vapor flow, Xw is the Martinelli parameter for laminar liquid-laminar vapor flow, Xq is thermodynamic equilibrium quality, z is the streamwise coordinate, fi is the viscosity, p is the density, <7 is the surface tension the subscripts are L for saturated fluid, LG for property difference between saturated vapor and saturated liquid, G for saturated vapor, sp for singlephase, and tp for two-phase. 

Carey van P (1992) Liquid-vapor phase-change phenomena. An introduction to the thermophysics of vaporization and condensation processes in heat transfer equipment. Hemisphere, New York Celata GP, Cumo M, Mariani A (1997) Experimental evaluation of the onset of subcooled flow boiling at high liquid velocity and subcoohng. Int J Heat Mass Transfer 40 2979-2885 Celata GP, Cumo M, Mariani A (1993) Burnout in highly subcooled water flow boiling in small diameter tubes. Int J Heat Mass Transfer 36 1269-1285 Chen JC (1966) Correlation for boiling heat transfer to saturated fluids in convective flow. Ind Eng Chem Process Des Develop 5 322-329... 

The diazotization reaction can also be initiated via the vapor phase, e. g. with ethyl nitrite that can be generated in one trough of a twin-trough chamber by adding a few drops of cone, hydrochloric acid to a mixture of ethanol and saturated aqueous sodium nitrite solution (1 + 1) [3] the less volatile amyl nitrite can be used as an alternative [3]. 

Trans-4-Octene oxide 1885 (1.2 mmol), then hexamethyldisilane 857 (1.8 mmol) in 5 mL HMPA, are added, at 65 °C under argon, to 0.2 mmol potassium methox-ide in 10 mL anhydrous HMPA. After 3 h stirring at 65 °C and cooHng to room temperature saturated aqueous NaCl solution is added to the reaction mixture, which is then extracted with pentane. The pentane extracts are combined and dried with Na2S04 and analyzed by vapor phase chromatography (VPC) to reveal the formation of 99% cis 4-octene 1887 [103] (Scheme 12.71). 

One of the most crucial influencing factors in planar chromatography is the vapor space and the interactions involved. The fact that the gas phase is present, in addition to stationary and mobile phases, makes planar chromatography different from other chromatographic techniques. Owing to the characteristic of an open system the stationary, mobile, and vapor phases interact with each other until they all are in equihbrium. This equilibrium is much faster obtained if chamber saturation is employed. This is the reason for differences in separation quality when saturated and unsaturated chambers are used. However, the humidity of the ambient air can also influence the activity of the layer and, thus, separation. Especially during sample application, the equihbrium between layer activity and relative humidity of the... 

FIGURE 5.28 Influencing factors of chamber climate in a trough chamber 1 — evaporation of low volatile components of the mobile phase from the trough bottom until saturation, 2 — sorptive saturation, 3 — evaporation from the layer, 4 — adsorption of the vapor phase. 

The discussed effects, such as evaporation and adsorptive saturation, are prevented by placing a counter plate at a distance of one or a few millimeters from the chromatographic layer. The development with such a reduced vapor phase in the so-called sandwich chambers (S-chambers) can improve the separation. The glass-backed 20 X 20 cm plate forms one wall of the chamber with the adsorbent facing inward. A glass plate with spacers, called counter plates, is clamped to this plate and forms the other wall of the chamber (Figure 5.31, left [32]). 

It is shown that similar effects are observed in case of gas or vapor phase media under condition of availability of saturated vapor in the liquid forming a thin layer on the smface of a semiconductor adsorbent. 

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