Sharpness ratings

Figure 8.4 shows the steady-state effect of po2 and imposed catalyst potential Uwr on the rate of C2H4 oxidation and compares the results with the open-circuit kinetics. The sharp rate decline for high po2 values is due to the formation of surface Rh oxide.13 Increasing UWr causes a significant increase in the oxygen partial pressure, po2, where oxide forms and thus causes a dramatic increase in r for intermediate (1 to 2.5 kPa) Po2 values. For low P02 values (reduced surface) the effect of Uwr is moderate with p values up to 2. For highp02 values (po2>Po2 > oxidized surface) Uwr has practically no effect on the rate. 

Figure 5. Effect of percent add-on sharpness ratings of polyester/cotton, 50/50 fabrics at various acrylo-urethane oligomer (MW 6000) levels 2.5% Graphtol...

Figure 7. Effect of Cab-O-Sil level on sharpness ratings of fabrics at various depths of engraving 15% acrylo-urethane oligomer, P/C 50/50, Graphtol Blue 6825. (HJ 3 mil 6% pigment (A) 2 mil 6% pigment (9) 1 mil 6% pigment (Q) 3 mil 2.5% pigment (A) 2 mil 2.5% pigment (0)1 mil 2.5% pigment.

Thereafter the rate becomes very low and negative order in po - It has been shown that this sharp rate transition is due to the formation of a catalytically inactive surface Rh oxide [137]. As shown in Figure 40 (inset) increasing CAvr and thus causes a pronounced increase in Pq and thus a dramatic rate increase at intermediate po values with p values up to 100. Exactly the same behavior is... 

Sharp rate of rise of pressure drop. A sharp rate of rise of pressure drop with vapor rate may be an even more sensitive flooding indicator than the magnitude of pressure drop. The flood point can be inferred from a plot of pressure drop against vapor or liquid flow rate, and is the point where the slope of the curve changes significantly (Figs. 14.3,14.4). In tray columns, the slope change can be relatively mild (curve 1 in Fig,... 

Using a rotational-torsional surface viscosimeter, the surface shear viscosity of the C15-C20 straight-chain fatty acids have been determined (Moo-Young et aL, 1981). The even fatty acids were found to show a surface-Newtonian behaviour, with s-values of 1.5, 2 and 3 mN s/m for the Ci, Cis and C20 members respectively. The odd adds, however, showed a surface-pseudoplastic behaviour. Thus C17 gave decreasing surface shear viscosity up to a sharp rate of 8 s , and beyond that value the viscosity remained constant at about 0.6 mN s/m. These data indicate different monolayer structures of the even and odd members. 

Interfacial tension measurement, both static and dynamic, provide clues about the usefulness of the surfactant as an emulsifier for a given system of oil and water. Not only is the sharp decrease in interfacial tension desirable, but it is also important to produce the minimum tension possible from a given surfactant. In fact the results of interfacial tension measurements can provide information about the effectiveness and efficiency of surfactants for a given system. A sharp decrease in interfacial tension with the increase in concentration of surfactant indicates that the surfactant is effective, whereas one that causes minimum interfacial tension although not with a sharp rate would be considered efficient. Depending on the requirements, one can use the effective or the efficient surfactant for a given formulation of paints, inks, and polishes. Interfacial data of surfactants can be used as the main criteria for quality by the users of surfactants. 

There is now a simple explicit expression for the vapor rate in a single column in terms of the feed to the column. In order to use this expression to screen column sequences, the vapor rate in each column must be calculated according to Eq. (5.8), assuming a sharp separation in each column, and the individual vapor rates summed. 

An interesting point is that AH itself varies with r [10].] As is the case when P is varied, the rate of nucleation increases so strongly with the degree of supercooling that a fairly sharp critical value exists for T. Analogous equations can be written for the supercooling of a melt, where the heat of fusion AH/ replaces AH . 

Although it is hard to draw a sharp distinction, emulsions and foams are somewhat different from systems normally referred to as colloidal. Thus, whereas ordinary cream is an oil-in-water emulsion, the very fine aqueous suspension of oil droplets that results from the condensation of oily steam is essentially colloidal and is called an oil hydrosol. In this case the oil occupies only a small fraction of the volume of the system, and the particles of oil are small enough that their natural sedimentation rate is so slow that even small thermal convection currents suffice to keep them suspended for a cream, on the other hand, as also is the case for foams, the inner phase constitutes a sizable fraction of the total volume, and the system consists of a network of interfaces that are prevented from collapsing or coalescing by virtue of adsorbed films or electrical repulsions. 

As is made evident in the next section, there is no sharp dividing line between these two types of adsorption, although the extremes are easily distinguishable. It is true that most of the experimental work has tended to cluster at these extremes, but this is more a reflection of practical interests and of human nature than of anything else. At any rate, although this chapter is ostensibly devoted to physical adsorption, much of the material can be applied to chemisorption as well. For the moment, we do assume that the adsorption process is reversible in the sense that equilibrium is reached and that on desorption the adsorbate is recovered unchanged. 

Tr(/ ), that would provide an optimal eooling strategy. This last observation is the enix of our eooling theory and puts into sharp perspeetive the role played by the external field while the external field eaimot itself ehange the purity of the system it ean perfomi purity-preserving transformations whieh subsequently affeet the rate of ehange of purity. 

The simplest manifestation of nonlinear kinetics is the clock reaction—a reaction exliibiting an identifiable mduction period , during which the overall reaction rate (the rate of removal of reactants or production of final products) may be practically indistinguishable from zero, followed by a comparatively sharp reaction event during which reactants are converted more or less directly to the final products. A schematic evolution of the reactant, product and intenuediate species concentrations and of the reaction rate is represented in figure A3.14.2. Two typical mechanisms may operate to produce clock behaviour. 

Figure A3.14.2. Characteristic features of a clock reaction, illustrated for the Landolt reaction, showing (a) variation of product concentration witii induction period followed by sharp reaction event (b) variation of overall reaction rate witli course of reaction.

---