Liquids pure, viscosity measurement

Cone and plate systems (Fig. 3.5) allow the build up of a defined constant shear field with only a very small amount of polymer liquid. Because they require high precision motor drives and sensors and because of the high error when wrong distance alignments are used, cone and plate systems are mostly found in expensive rheometers that are capable of more sophisticated kinds of stress fields than the pure shear flow. Nevertheless, they can be used for pure viscosity measurements. 

Viscosity measurement or rheology. Viscosity is an important property of many fluids, particularly consumer products. Pancake syrup that does not appear thick or a runny shampoo has little consumer appeal. Viscosity is also an important measurement for liquid polymers. It is a measure of polymer chain length and branching. On the other hand, viscosity does not have the sensitivity to detect small amounts of impurities in pure substance. 

The shear-mode acoustic wave sensor, when operated in liquids, measures mass accumulation in the form of a resonant frequency shift, and it measures viscous perturbations as shifts in both frequency and dissipation. The limits of device operation are purely rigid (elastic) or purely viscous interfaces. The addition of a purely rigid layer at the solid-liquid interface will result a frequency shift with no dissipation. The addition of a purely viscous layer will result in frequency and dissipation shifts, in opposite directions, where both of these shifts will be proportional to the square root of the liquid density-viscosity product v Pifti-... 

Another very useful approach to molar mass information of complex polymers is the coupling of SEC to a viscosity detector [55-60]. The viscosity of a polymer solution is closely related to the molar mass (and architecture) of the polymer molecules. The product of polymer intrinsic viscosity [r ] times molar mass is proportional to the size of the polymer molecule (the hydrodynamic volume). Viscosity measurements in SEC can be performed by measuring the pressure drop AP across a capillary, which is proportional to the viscosity r of the flowing liquid (the viscosity of the pure mobile phase is denoted as r 0). The relevant parameter [r ] is defined as the limiting value of the ratio of specific viscosity (qsp= (n-noVflo) and concentration c for c—> 0 ... 

The surface tension of pure ozone was determined by the capillary rise method in the apparatus used for viscosity measurements. The ratio of the capillary rise of liquid ozone to that of water at 20° C. was measured and zero contact angle was assumed. Results at —183° and —195.5° C. are given in Table III. The parachor for... 

The results of nuclear magnetic resonance, infrared, dielectric, and viscosity measurements on pure mono- and dihydric alcohols and alcohol-water systems are discussed in terms of the information they provide on the nature and extent of molecular association in these systems. This association leads to the formation of dimeric and multimeric species in the pure liquid alcohols, an unexpectedly high solubility of water in the long-chain alcohols, and the occurrence of a liquid crystalline phase in 1,2-diol-water systems. 

Viscosity measurements were performed before each set of two-phase experiments to estimate the actual viscosity values of the ionic liquids. Although the ionic liquids used in this research are hydrophobic, they still absorb small amounts of water (hygroscopic) depending on the initial nitric acid concentration in the aqueous phase. The absorbed water is expected to affect their viscosity (Billard et al. 2011b). To estimate the viscosity of the saturated ionic liquid, prior to the experiments the ionic liquids were stirred with water or nitric acid solutions. Saturation was confirmed, when the viscosity did not change over time. The viscosities of the ionic liquids were measured using a digital Rheometer DV-III Ultra (Brookfield) at room temperature and were found to decrease by 15-20 % when saturated with aqueous phase compared to the values of pure ionic liquids. 

The glass transition temperature of the pure solvent 7 (0), obtained by extrapolation (m -> 0), is found to be independent of the solutes in a given solvent and equal to that from viscosity measurements, which shows that the glass transition temperature is the appropriate reference temperature for transport processes in the liquid state. Using this result in Eq. (82) yields the further important... 

Viscosity is a measure of the friction (resistance to mechanical movement) of a fluid. In the case of liquids, the viscosity of a solution is different from the pure solvent and is dependent on the nature and concentration of the solute. The following Staudinger equation (Tanford 1961 Clapp, Emerson, and Olness 1990 Stevenson 1994) allows to estimate molecular weights ... 

The polyphasic region contains a three-phase zone surrounded by three two-phases zones. Systems whose composition lies in the three-phase zone separate into an amphi-phUe-rich phase (m), which is in the middle of the diagram at the boundary of the single-phase region, and two excess phases, which are essentially pmre aqueous phase and pure oil. This amphiphile-rich phase, which is found to obey, in most cases, the definition proposed for a bicontinuous microemulsion or a liquid crystal, has been called a middle phase because its intermediate density makes it appear in between the oil and water phases in a test tube. Because the middle phase is at equilibrium with both excess phases, it cannot be diluted either by water or oil, and it is thus neither water nor oil-continuous. This is another hint of the bicontinuous nature of this phase, as conductivity and viscosity measurements and other experimental evidences have shown [20-22,37-40]. 

The introduction of the coefficient of viscosity measured by flow in the case where the particle moves in a pure liquid has been experimentally justified by Svedberg and Eriksson-Quensel (1936), who showed that the same sedimentation constant of Helix hemocyanin is obtained in mixtures of heavy and ordinary water in various proportions if corrections for density and viscosity are introduced. In the cases where the solvent is a dilute electrolyte solution, the necessity of a correction for the increased viscosity has not been completely proved. The corrections which are applied are in most cases sufficiently small to fall within the error of the determinations since for solutions of buffer below half-molar concentration the ratio i7bu o-/> watei does not exceed unity by more than 5%. 

Examples of Newtonian liquids are water, ether, glycerine, benzene, mercury and most pure simple liquids. Values of the coefficient of viscosity, measured at 291K are given in Table 4.2. 

It was made clear in Chapter II that the surface tension is a definite and accurately measurable property of the interface between two liquid phases. Moreover, its value is very rapidly established in pure substances of ordinary viscosity dynamic methods indicate that a normal surface tension is established within a millisecond and probably sooner [1], In this chapter it is thus appropriate to discuss the thermodynamic basis for surface tension and to develop equations for the surface tension of single- and multiple-component systems. We begin with thermodynamics and structure of single-component interfaces and expand our discussion to solutions in Sections III-4 and III-5. 

L. L. Blyler and T. K. Kwei [39] proposed the direct opposite (to 4). In their reasoning, they proceeded from the known and generally acceptable Doolittle equation, which puts liquid viscosity in exponential dependence on the inverse value of the free volume of the latter. According to [39], gas has a volume of its own, the value of which it contributes to the free volume of the polymer when it dissolves therein as a result, viscosity falls. The theoretical formula obtained by the authors was experimentally confirmed in the same work. The authors measured pressure values at the entrance of cylindrical capillaries, through which melts of both pure polyethylene, and polyethylene with gas dissolved in it, extruded at a constant rate. 

Iwahashi, M. Hayashi, Y. Hachiya, N. Matsuzawa, H. Kobayashi, H., Self-association of octan-l-ol in the pure liquid state and in decane solutions as observed by viscosity, selfdiffusion, nuclear magnetic resonance and near-infrared spectroscopy measurements, J. Chem. Soc. Faraday Trans. 89, 707-712 (1993). 

The viscosity coefficients at dislocation cores can be measured either from direct observations of dislocation motion, or from ultrasonic measurements of internal friction. Some directly measured viscosities for pure metals are given in Table 4.1. Viscosities can also be measured indirectly from internal friction studies. There is consistency between the two types of measurement, and they are all quite small, being 1-10% of the viscosities of liquid metals at their melting points. It may be concluded that hardnesses (flow stresses) of pure... 

Intrinsic resistance to dislocation motion can be measured in either of two ways direct measurements of individual dislocation velocities (Vreeland and Jassby, 1973) or by measurements of internal friction (Granato, 1968). In both cases, for pure simple metals there is little or no static barrier to motion. As a result of viscosity there is dynamic resistance, but the viscous drag coefficient is very small (10" to 10" Poise). This is only 0.1 to 1 percent of the viscosity of water (at STP) and about 1 percent of the viscosity of liquid metals at their... 

The coefficients are defined for infinitely dilute solution of solute in the solvent L. However, they are assumed to be valid even for concentrations of solute of 5 to 10 mol.%. The relationships are available for pure solvent, and could be used for mixture of solvents composed of molecules of close size and shape. They all refer to the solvent viscosity which can be estimated or measured. Pressure has a negligible influence on liquid viscosity, which decreases with temperature. As a consequence, pressure has a weak influence on liquid diffusion coefficient conversely, diffusivity increases significantly with temperature (Table 45.4). For mixtures of liquids, an averaged value for the viscosity should be employed. 

Kxtemivc work has been done on measuring liquid viscosities of the pure Penh. indthcu aqueous solutions Fig-uie 24-9 is a plm of ilw pure ncid viscosities up to I50T. Figures 24-U> 24-11. and 24 12 present aqueous solution data from the Iniwiuttonul CrUiait rj/tfri. ... 

This unit describes a method for measuring the viscosity (r ) of Newtonian fluids. For a Newtonian fluid, viscosity is a constant at a given temperature and pressure, as defined in unit hi. i common liquids under ordinary circumstances behave in this way. Examples include pure fluids and solutions. Liquids which have suspended matter of sufficient size and concentration may deviate from Newtonian behavior. Examples of liquids exhibiting non-Newtonian behavior (unit hi. i) include polymer suspensions, emulsions, and fruit juices. Glass capillary viscometers are useful for the measurement of fluids, with the appropriate choice of capillary dimensions, for Newtonian fluids of viscosity up to 10 Pascals (Newtons m/sec 2) or 100 Poise (dynes cm/sec 2). Traditionally, these viscometers have been used in the oil industry. However, they have been adapted for use in the food industry and are commonly used for molecular weight prediction of food polymers in very dilute solutions (Daubert and Foegeding, 1998). There are three common types of capillary viscometers including Ubelohde, Ostwald, and Cannon-Fenske. These viscometers are often referred to as U-tube viscometers because they resemble the letter U (see Fig. HI.3.1). 

Capillary viscometers are ideal for measuring the viscosity of Newtonian fluids. However, they are unsuitable for non-Newtonian fluids since variations in hydrostatic pressure during sample efflux results in variations in shear rate and thus viscosity. This unit contains protocols for measuring the viscosity of pure liquids and solutions (see Basic Protocol) and serums from fruit juices and pastes (see Alternate Protocol). 

This protocol describes a method for measuring the viscosity of pure liquids and solutions by capillary viscometry. The sample is loaded into a Cannon-Fenske viscometer. The time required for the sample to flow between two time points on the viscometer is used to calculate the kinematic viscosity or viscosity. 

This method is an adaptation of the Basic Protocol for measuring the viscosity of pure liquids and solutions. The °brix (unithi.4) of the sample is adjusted to a desired value by dilution. In many protocols, a nominal value of 5 °brix is the accepted target value for dilution. The sample is then filtered to remove particles that would plug the capillary tube of the viscometer, and the serum viscosity is measured in a Cannon-Fenske viscometer. 

Viscosity and density of the component phases can be measured with confidence by conventional methods, as can the interfacial tension between a pure liquid and a gas. The interfacial tension of a system involving a solution or micellar dispersion becomes less satisfactory, because the interfacial free energy depends on the concentration of solute at the interface. Dynamic methods and even some of the so-called static methods involve the creation of new surfaces. Since the establishment of equilibrium between this surface and the solute in the body of the solution requires a finite amount of time, the value measured will be in error if the measurement is made more rapidly than the solute can diffuse to the fresh surface. Eckenfelder and Barnhart (Am. Inst. Chem. Engrs., 42d national meeting, Repr. 30, Atlanta, 1960) found that measurements of the surface tension of sodium lauryl sulfate solutions by maximum bubble pressure were higher than those by DuNuoy tensiometer by 40 to 90 percent, the larger factor corresponding to a concentration of about 100 ppm, and the smaller to a concentration of 2500 ppm of sulfate. 

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