Apparent property value, experimentally determined

An experimentally determined value is referred to as an apparent property value if it depends on system parameters, for instance, the rate at which the experiment is performed. An example of a rate dependent property is viscosity. By definition, the intrinsic value of a rate dependent property is the extrapolated value in regards of an infinite time period over which the property is obtained. There are properties that are combinations of truly independent properties, e.g., the material density as the mass per unit volume. The properties of foremost interest are intensive properties, i.e., properties that are independent of the size of a system. 

As was noted above, the model parameter K is the true constant whose value is determined by the molecular properties of the system. Since constant K is the characteristic of a single PQ molecule, its value does not depend on the volume of a whole system. On the other hand, the experimentally determined conventional equilibrium constant in the general case, is not a real constant. This constant, being calculated from the measured experimental concentrations of particles, will depend on the volume confining these particles. In the thermodynamic limit only, when we can neglect the fluctuations, the apparent equilibrium constant would be equal to the real one, app = = const. 

In spite of a large amount of experimental data, unfortunately due to absence of heat capacities and sometimes viscosities, only restricted compressibility properties can be determined and they are also limited to one temperature. In Table 5.15 are presented values of A m) and u m) at 25 °C (for other temperatures they are available in the original papers) and they permit to evaluate the isentropic compressibility coefficients Kjj -yn) and the apparent molar compressibilities K (T m) using Eqs. (5.52). 

Reliable determination of all three functions depends on the information content associated with the experiments. The conventional experimental design does not provide sufficient information to determine all three functions accurately [34], Another consideration is that conventional analyses are all based on the assumption that the sample is uniform, and use an average value for porosity and an apparent value for permeability. Clearly, these properties vary spatially, and failure to account for the effects of spatial variations in the properties will lead to errors in the estimates of the functions [16]. 

In addition to the interphase potential difference V there exists another potential difference of fundamental importance in the theory of the electrical properties of colloids namely the electro-kinetic potential, of Freundlich. As we shall note in subsequent sections the electrokinetic potential is a calculated value based upon certain assumptions for the potential difference between the aqueous bulk phase and some apparently immobile part of the boundary layer at the interface. Thus represents a part of V but there is no method yet available for determining how far we must penetrate into the boundary layer before the potential has risen to the value of the electrokinetic potential whether in fact f represents part of, all or more than the diffuse boundary layer. It is clear from the above diagram that bears no relation to V, the former may be in fact either of the same or opposite sign, a conclusion experimentally verified by Freundlich and Rona. 

In non-Newtonian fluids K a also depends on their physical and rheoiogical properties. The contribution of the latter has been normally expressed in terms of the apparent viscosity, and there is general agreement that this dependence is of the form Kj a 0(11 ) % where z can take values between 0.4 to 0.7. In the case of viscoelastic materials, inclusion of the fluid rheology is less straightforward. Several authors have tried to include the effect of elasticity via the Deborah number, which for stirred tanks is defined as the product of a characteristic time of the fluid and impeller speed. However, determination of the former is not an easy task because it is not always possible to characterize experimentally the viscoelastic properties of the fluid. Determination of the characteristic time of the fluid from experimental shear viscosity vs. shear rate curves [29] and from interpolation of published experimental data on viscoelastic properties [30] has been tried in the past. However, values thus obtained are not necessarily representative of the actual behavior of the liquid. At present, inclusion of the Deborah number in dimensional or dimensionless correlations has not been completely successful. 

The theory of Kamide (1990) allows determining the properties of the polymeric membrane covering a particle both in terms of number of pores, their conformation and apparent diffusivity. Basically, it is necessary to know the volumes ratio/ between solvent and polymer. These two phases are respectively identified as poor and rich phases. In our formulation and experimental activity we worked with ethylcellulose polymer and cyclohexane solvent. Consequently, the specific values defined in the following refer to such pairing. The membrane is formed by the separation of the polymer from the poor phase and the consequent coagulation of the polymer particles. It is possible to outline three main steps for the membrane formation ... 

The sharpness of the inflection point at the CMC in plots of the concentration dependence of a suitable physical property is dependent on the relative values of the mass-action parameters, and a. For low n and a gradual change in the physical property in the region of the CMC is predicted. Simulation of lightscattering curves using selected combinations of the mass-action parameters is a useful way of determining whether the apparent absence of a CMC in experimental curves is due to a combination of low n and values or arises from... 

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