Curves, partial pressure

Figure 1.1 Partial pressure diagram of ethanol, C2H5OH, in logarithmic scale. The small deviation of the curve partial pressure p versus temperature T from linearity demonstrates that p(T) is not exactly exponential. The ethanol concentration scale c as a volume ratio refers to an ambient pressure of 1.013 105 Pa.

Phase relationships ia the system K O—B2O2—H2O have been described and a portion of the phase diagram is given ia Figure 8. The tetrahydrate, which can be dried at 65°C without loss of water of crystallisation, begias to dehydrate between 85 and 111°C, depending on the partial pressure of water vapor ia the atmosphere. This conversion is reversible and has a heat of dehydration of 86.6 kj/mol (20.7 kcal/mol) of H2O. Thermogravimetric curves iadicate that two moles of water are lost between 112 and 140°C, one more between 200 and 230°C and the last between 250 and 290°C (121). 

Adsorption Plots. Isotherm plots are the most common method of presenting adsorption data. An isotherm is a curve of constant temperature the adsorbed water content of the adsorbent is plotted against the water partial pressure in equiHbrium with the adsorbent. An isostere plot shows curves of constant adsorbed water content the vapor pressure in equiHbrium with the adsorbent is plotted against temperature. Figure 13 shows isosteres for the three primary adsorbents described previously. In this case, the dew points for the three adsorbents are plotted at 0.5, 5, and 10 kg... 

The wet bulb or saturation temperature curve indicates the maximum weight of vapor that can be carried by a unit weight of dry gas. For any temperature on the abscissa, saturation humidity is found by reading up to the saturation temperature curve, then across to the ordinate, kg/kg dry air. At saturation, the partial pressure of vapor in the gas is the vapor pressure of the hquid at the specific temperature ... 

FIG. 28-1 Operating limits for steels in hydrogen service, Each steel is suitable for use under hydrogen-partial-pressure-temperature conditions below and to the left of its respective curve, (Coutiesy of National Association of Conosion Engineers)... 

To avoid decarburization and Assuring of the carbon and low-alloy steels, which is cumulative with time and, for all practical purposes irreversible, the limitations of the Nelson Curves should be followed religiously, as a minimum. Suitable low-alloy plate materials include ASTM-A204-A, B, and C and A387-A, B, C, D, and E, and similarly alloyed materials for pipe, tubes, and castings, depending upon stream temperatures and hydrogen partial pressures, as indicated by the Nelson Curves. 

Partial pressure, 18 Particle size, 484 Perfect gas equation, 15, 32 Performance curve, 3 axial, 232... 

If, instead, the air is damped adiabatically with the wet cloth, so that the state of the air varies, the cloth will settle to a slightly different temperature. Each state of air (0, x) is represented by a certain wet bulb temperature 6, which can be calculated from Eq. (4.116) or its approximation (4.123), when the partial pressures of water vapor are low compared with the total pressure. When the state of air reaches the saturation curve, we have an interesting special case. Now the temperatures of the airflow and the cloth are identical. This equilibrium temperature is called the adiabatic cooling border or the thermodynamic wet bulb temperature (6 ). 

In this form, Alhas the units of torr.) The relationship defined by Equation (A15.4) plots as a hyperbola. That is, the MbOg saturation curve resembles an enzyme substrate saturation curve. For myoglobin, a partial pressure of 1 torr for jbOg is sufficient for half-saturation (Figure A15.1). We can define as the partial pressure of Og at which 50% of the myoglobin molecules have a molecule of Og bound (that is, F= 0.5), then... 

The water curve intersects the particular organic compound and at that point the temperature is the one at which the steam distillation can take place, because the partial pressures are additive at this point. For example. 

The corresponding values of the constants are listed in Table IX.Using these values and substituting the conversions for partial pressures as in the hydrogenation of phenol (see p. 32), by numerically solving the system of five differential equations we obtained the curves presented in Fig. 9, which agreed well with experimental points. 

In actual experiments we do not usually observe directly the desorbed amount, but rather the derived read-out quantities, as is the time dependence of the pressure in most cases. In a closed system, this pressure is obviously a monotonously increasing function of time. In a flow or pumped system, the pressure-time dependence can exert a maximum, which is a function of the maximum desorption rate, but need not necessarily occur at the same time due to the effect of the pumping speed S. If there are particles on the surface which require different activation energies Ed for their desorption, several maxima (peaks) appear on the time curve of the recorded quantity reflecting the desorption process (total or partial pressure, weight loss). Thereby, the so-called desorption spectrum arises. It is naturally advantageous to evaluate the required kinetic parameters of the desorption processes from the primarily registered read-out curves, particularly from their maxima which are the best defined points. 

Konowalow s curves for three typical mixtures are shown in Figs. 71-73. Each total pressure curve may be regarded as built up from two partial pressure curves, the ordinate of every point being the sum of the partial pressures over the liquid having the composition of the... 

In the geometrical representation of the partial pressures of I., we have on the right the straight line PiQ corresponding with (1), and on the left one or other of the three initial curves 0a, Ob, 0c, corresponding with the equation 7ri = Pi and the inequalities 7Ti < Pi, 7Ti > Pi, respectively. 

The complete partial pressure curve will therefore be one of the three types OcQPi, OaQPi, O QPi, which may be denoted by c, a, b, and called neutral, positive, and negative, respectively. 

The gradients of the partial pressure curves at the abscissa corresponding to a maximum or a minimum must be equal but of opposite sign. For if P is the total pressure,... 

If one curve, say pi = total pressure curve, is known from (4) for all concentrations, and conversely if the total pressure curve, n = F (x), is known, both partial pressure curves are determined when (4) is written in the form ... 

The vapour-pressure curves of binary liquid mixtures have been considered from another point of view by Dolezalek (Zeitscher. physik. Chem. 64, 727, (1908)), who starts out with the very simple assumption that the partial pressure of each component is proportional to its concentration in the liquid phase, provided no chemical change occurs when the liquids are mixed, and that neither component is polymerised in the liquid state. Thus ... 

A partial pressure curve which is concave to the concentration axis, i.e. a positive curve, indicates the dissociation of a polymerised component, whilst a curve which is convex to the same axis, i.e., a negative curve, indicates the formation of a chemical compound of the two components. In the first case the concentration of the constituent passing into the vapour would be increased, in the second case reduced, by the assumed change. As examples, Dolezalek quotes ... 

Emil Bose (1910) maintains that Zawidski s calculations, with Margules solution with only a few coefficients, are not satisfactory, and proposes to find the partial pressures by a graphical method which consists in drawing the two partial pressure curves so that the sum of their ordinates is everywhere equal to the ordinate of the (known) total pressure curves. The Duhem equation shows that pi, p2 are positive, continuous, and smgle-valued functions of a , so that only one decomposition of the total pressure curve has any physical significance, and for every value of x ... 

FIGURE 9.18 The variation of the extent of saturation of myoglobin (Mb) and hemoglobin (Hbl with the partial pressure of oxygen. The different shapes of the curves account for the different biological functions of the two proteins. 

The chloroform/polystyrene solution exhibits highly nonideal behavior. As shown by curve C in Figure 4, the x parameter for this solution rises from a low value to a high value as solvent concentration increases. However, as shown in Figure 5, the partial pressure of chloroform above a mixture of... 

In the A sector (lower right), the deposition is controlled by surface-reaction kinetics as the rate-limiting step. In the B sector (upper left), the deposition is controlled by the mass-transport process and the growth rate is related linearly to the partial pressure of the silicon reactant in the carrier gas. Transition from one rate-control regime to the other is not sharp, but involves a transition zone where both are significant. The presence of a maximum in the curves in Area B would indicate the onset of gas-phase precipitation, where the substrate has become starved and the deposition rate decreased. 

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