Table liquids/solids, 286 Viscosity

Table 4.1 presents typical values of viscosities of some common materials. One can see from this table that viscosity varies over several orders of magnitude. One may also note that, although the table lists a viscosity for glasses, the magnitude of the viscosity clearly suggests that the deformation of glasses at room temperatures will be extremely small so glasses are best treated as solids under normal conditions. (Recall the discussion in Section 4.1c of time scales and their relation to whether a substance is defined as a liquid or a solid.) Typical rates of shear for some familiar processes are shown in Table 4.2. 

NIST/ASME Steam Properties Database versiou 2.21 http //www.nist.gov/srd/nistlO.cfm (accessed November 10, 2010) (purchase required). Thermophysical properties include in the STEAM Database temperature, Helmholtz energy, thermodynamic derivatives, pressure, Gibbs energy, density, fugacity, thermal conductivity, volume, isothermal compressibility, viscosity, dielectric constant, enthalpy, volume expansivity, dielectric derivatives, internal energy, speed of sound, Debye-Hlickel slopes, entropy, Joule-Thomson coefficient, refractive index, heat capacity, surface tension. The STEAM database generates tables and plots of property values. Vapor-liquid-solid saturation calculations with either temperature or pressure specified are available. 

A general reference often consulted today for the physical and chemical properties of common chemicals is Lange s Handbook of Chemistry (Dean 1999), which lists many chemical compounds and their most important properties. It is organized into separate chapters of Physical constants of organic molecules with 4300 compounds and Physical constants of inorganic molecules, and lists each compound alphabetically by name. Some of these properties are very sensitive to temperature, but less sensitive to pressure, and they are listed as tables, or more compactly as equations of the form /(T) for example, liquid heats of evaporation, heat capacities of multi-atom gases, vapor pressures over liquids, liquid and solid solubilities in liquids, and liquid viscosities. Some of these properties are sensitive both to temperature and pressure. 

Dynamic techniques are used to determine storage and loss moduli, G and G respectively, and the loss tangent, tan 6. Some instruments are sensitive enough for the study of liquids and can be used to measure the dynamic viscosity rj. Measurements are made as a function of temperature, time, or frequency, and results can be used to determine transitions and chemical reactions as well as the properties noted above. Dynamic mechanical techniques for solids can be grouped into three main areas free vibration, resonance-forced vibrations, and nonresonance-forced vibrations. Dynamic techniques have been described in detail (242,251,255,266,269—279). A number of instruments are listed in Table 8. Related ASTM standards are listed in Table 9. 

With the exception of monomer 11 Id, all of the monomers were crystalline solids with melting points ranging from 95 to 157 °C (Table 21). When molten, they formed low viscosity liquids which allowed these monomers to be readily processed into their homopolymers at higher temperature (200 °C). 

Expert opinions differ somewhat on this factor. As a first approximation, the impeller can be placed at 1/6 the liquid level off the bottom. In some cases there is provision for changing the position of the impeller on the shaft. For off-bottom suspension of solids, an impeller location of 1/3 the impeller diameter off the bottom may be satisfactory. Criteria developed by Dickey (1984) are based on the viscosity of the liquid and the ratio of the liquid depth to the tank diameter, h/D,. Whether one or two impellers are needed and their distances above the bottom of the tank are identified in this table ... 

The properties of Ge(OR)4 allow them to be considered more likely to be the esters of an inorganic acid than metal alkoxides these are colorless volatile liquids, containing monomeric tetrahedral molecules. The solid crystalline form is known only for R = Bu, OC6Hnc, and also 2,6-substituted phenoxides. All the members of the Ge(OR)4 homologous series are characterized by thoroughly determined physical characteristics — density, refraction index, surface tension, viscosity (and calculated parachor values), dipole moments in different solvents [222, 857, 1537] (Table 12.9). The results of the investigation of vapor pressure, density, viscosity polytherms, and so on. permitted rectification for the preparation of samples of high purity for sol-gel and MOCVD applications [682, 884]. 

Kinetics and Phase Behavior - Table IV represents a simplified picture of the situation however, some polymerizations go through several phase changes in the course of the reaction. For example, in the bulk polymerization of PVC, the reaction medium begins as a low viscosity liquid, progresses to a slurry (the PVC polymer, which is insoluble in the monomer, precipitates), becomes a paste as the monomer disappears and finishes as a solid powder. As might be expected, modelling the kinetics of the reaction in such a situation is not a simple exercise. 

Gas holdup is an important hydrodynamic parameter in stirred reactors, because it determines the gas-liquid interfacial area and hence the mass transfer rate. Several studies on gas holdup in agitated gas-liquid systems have been reported, and a number of correlations have been proposed. These are summarized in Table VIII. For a slurry system, only a few studies have been reported (Kurten and Zehner, 1979 Wiedmann et al, 1980). In general, the gas holdup depends on superficial gas velocity, power consumption, surface tension and viscosity of liquids, and the solid concentration. The dependence of gas holdup on gas velocity, power consumption, and surface tension of the liquid can be described as... 

Most of the common alcohols, up to about 11 or 12 carbon atoms, are liquids at room Physical Properties temperature. Methanol and ethanol are free-flowing volatile liquids with characteris-Of AI CO hols c frui y °dors. The higher alcohols (the butanols through the decanols) are somewhat viscous, and some of the highly branched isomers are solids at room temperature. These higher alcohols have heavier but still fruity odors. Propan-1 -ol and propan-2-ol fall in the middle, with a barely noticeable viscosity and a characteristic odor often associated with a physician s office. Table 10-2 lists the physical properties of some common alcohols. 

Lithium and its compounds may be used in fusion reactors in either liquid or solid form. Liquid Li is an excellent coolant with low density and viscosity, and with high heat capacity and thermal conductivity (Table 1). Consequently, it is used in many designs as a combined breeding material and coolant. However, hot molten Li can react violently with water or air under certain conditions. Hence, either strict engineering design must preclude large scale Li - air or water reactions, or another form of Li must be used. Both approaches have been studied. 

It has just been argued that the conductivities of simple ionic liquids, on the one hand, and liquid sihca and water, on the other, are vastly different because a fused salt is an unassociated liquid (it consists of individual particles) whereas both molten silica and water are associated liquids with network structures. What is the situation with regard to the viscosities of fused salts, water, and fused silica Experiments indicate that whereas water and fused NaCl have similar viscosities not far above the melting points of ice and solid salt, respectively, fused silica is a highly viscous liquid (Table 5.46). Here then is an interesting problem. 

Except for 1 -monoCN, which is a liquid at room temperature, the chlorinated naphthalenes are crystalline compounds. The melting point increases with increasing chlorine substitution with considerable variation within each homolo-gue group, cf. Table 2. The commercial PCN products, which occur as complex mixtures of isomers and homologues, are generally waxes with high compatibility with other materials. The solid products melt to liquids of extremely low viscosity [1]. 

As has already been described in Table 9.1, transport properties are enhanced in CXLs compared with conventional solvents. For example, diffusivities of solutes are enhanced up to 7-fold in carbon dioxide expanded methanol, with little effect being seen on the nature of the solute (benzene pyrazine). Therefore, it is thought that physical rather than chemical interactions are causing this phenomenon, including reduced viscosity and surface tension upon carbon dioxide addition. The solubility of solids, liquids and gases in CXLs will... 

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