Water-glycerol mixtures

The speed of wetting has been measured by running a tape of material that is wetted either downward through the liquid-air interface, or upward through the interface. For a polyester tape and a glycerol-water mixture, a wetting speed of about 20 cm/sec and a dewetting speed of about 0.6 cm/sec has been reported [37]. Conversely, the time of rupture of thin films can be important (see Ref. 38). 

A 50% glycerol-water mixture is flowing at a Reynolds numher of 1500 through a 25 mm diameter pipe. Plot the mean value of the heat transfer coefficient as a function of pipe length assuming that ... 

Cu-CuO% nanoparticles (with a content of about 10 wt.%) on titania are effective for the production of hydrogen under sacrificial conditions [176-178], A fairly low concentration of Cu (2.5 wt.%) was sufficient to allow promising H2 production from ethanol-water and glycerol-water mixtures in the case of CuO% nanoparticles encapsulated into porous titania [179]. A key limitation of this system is photocorrosion under oxidizing conditions (oxygen and carboxylic adds as by-products of partial oxidation of the sacrificial agent). However, in the presence of UV irradiation, Cu photodeposition can occur, preventing loss of Cu [179]. 

Calculate the distance a spherical particle of lead shot of diameter 0.1 mm settles in a glycerol/water mixture before it reaches 99 per cent of its terminal falling velocity. 

A 12 per cent glycerol—water mixture produced as a secondary product in a continuous process plant flows from the reactor at 4.5 MN/m2 and at 525 K. Suggest, with preliminary calculations, a method of concentration to 75 per cent glycerol in a plant where no low-... 

Figure Y shows the H NMRD profiles of water solutions of Fe(H20)g in 1 M perchloric acid at 298 K and in a glyceroTwater mixture (36). Only one dispersion is observed at about Y MHz. It corresponds to a correlation time Tc 3 X 10 s. The small increase of relaxivity above 20 MHz indicates that a field dependent is influential in the determination of at high field (see also Section II. C). From the fit to the SBM theory, is estimated to be around 5 x 10 s at room temperature, a value commonly found for small complexes in water solution and of the order expected for the mean lifetime between collisions with solvent molecules. The fit also provides a value for A = 0.095 cm , so that t o is calculated to be 9 x 10 s at room temperature. By increasing the viscosity through glycerol water mixture, it is shown that the relative influence of tb on with respect to becomes lower and lower with the increase in relaxivity in the high-field region being more and more evident. The fit of the profile acquired in the glycerol solution, performed by assuming that r, Ag, and A are not affected by the presence...

When the temperature is lowered and/or the viscosity of the solution is increased by using glycerol-water mixtures as solvent, the reorientational correlation time increases. Since the reorientational time is the correlation time for nuclear relaxation, the effects on the NMRD profile (Pig. 27) are (i) higher relaxivity values at low frequencies (ii) a shift toward lower... 

G. R. Fleming In simple liquids such as methanol and ethanol there is no evidence for relaxation times slower than expected from dielectric measurements. Glasses at room temperature clearly show time scales that are infinite on our measurement time scale. In complex liquids such as glycerol-water mixtures and ethylene glycol, we may observe time scales that are longer than dielectric relaxation, but further studies are required to confirm this. 

Other types of reactions which have been studied using FABMS include those catalyzed by enzymes. This application is particularly interesting because it represents for the first time a generally useful and molecularly specific probe with which to measure a wide variety of enzyme substrates and products. Two approaches have been successful, one in which the reaction is followed by the removal of aliquots of sample taken at timed intervals with subsequent analysis by FABMS and the other allowing the reaction to take place in a glycerol-water mixture on the probe directly inside the mass spectrometer. The choice of either method depends upon the application. If the prime interest is to analyze a substrate, for example, monitoring the release of amino acids from a polypeptide using an exopeptidase, then direct analysis inside the spectrometer may be preferred. If, on the other hand, the prime interest lies... 

The temperature dependence of k, was investigated and reported in Ref. [266], To obtain low-temperature data, samples were prepared in a 50% glycerol-water mixture. Figure 33 presents the temperature variation of k,. One can see from this Fig. that the electron transfer rate falls smoothly from the room temperature value to a non-zero value, kt = 9 + 4 s 1, which does not vary further from 170 down to 77 K. Data in the temperature-dependent region (T > 253 K) give the value Ea 2 kcal mol 1 for the Arrhenius activation energy. 

This development started with an observation of Pennings and Kiel (1965) that, when dilute solutions of polyethylene were cooled under conditions of continuous stirring, very fine fibres were precipitated on the stirrer. These fibres had a remarkable morphology a fine central core of extended CH2-chains, with an outer sheath of folded chain material. Electron microscopy revealed a beautiful "shish kebab" structure (see Fig. 19.16). Shish kebabs have also been observed in experiments without any stirring. For example, by washing polyethylene powder with xylene (Jamet and Perret, 1973) and by crystallising nylon 4 from a glycerol/water mixture (Sakaoku et al., 1968). 

The typical results of recent BDS studies of glycerol-water mixtures of 75 mol% of glycerol at different temperatures are presented in Fig. 25 [208]. Figure 26 shows that the temperature dependencies of the main relaxation... 

Figure 25. The imaginary parts of the dielectric spectra for a glycerol-water mixture (75 mol%) at various temperatures from 197 to 290 K with an interval of 3 K. (Reproduced with permission from Ref. 208. Copyright 2005, American Chemical Society.)...

Figure 26. Temperature dependence of xmax = 1 / (2nfmax) for a glycerol sample and its mixtures with water. The solid curves show the description by the VFT model, where values of the Vogel-Fulcher temperature (TV) are shown with the legend. The preexponential factor (xv) is almost independent with concentration In (xv) = —35.9 for 100mol% of glycerol, —36.1 for 95 to 65%, —36.2 for 60%, —36.3 for 60% to 45%, and —36.4 for 40mol% of glycerol-water mixtures. D = 22.7 for all concentrations presented here. (Reproduced with permission from Ref. 208. Copyright 2005, American Chemical Society.)...

The properties of H-bonded liquids were already reviewed in Section IV.D. Here we would like to continue the consideration of these samples this time with regard to their universal scaling behavior. We have separated this discussion into two parts, which consider two different kinds of glycerol-water mixtures. 

Moreover, the experimental data through dc-conductivity, the main process and the EW could be described by the new phenomenological function (114). If the concentration remains the same, only two variable parameters, As and x, with a set of constants, can describe the whole temperature dependence of spectra. The universality in the master plots of dielectric spectra for glycerol and glycerol-water mixtures has the same origin as elementary molecular processes... 

Figure 41. Typical dielectric spectra of 20 mol% of glycerol—water mixtures at (a) 185 K (supercooled state) and (b) 218 K (frozen state), where solid and dashed curves show the real and imaginary parts of complex dielectric permittivity. Each relaxation process in the frozen state was fitted by (114) and by Cole-Cole and Debye relaxation functions, respectively, in order to separate the main process, the process due to interfacial water, and the process due to ice. (Reproduced with permission from Ref. 244. Copyright 2005, American Chemical Society.)...

In order to estimate the ratio between the amounts of water in the mesoscopic glycerol-water domains, interfacial water, and ice in glycerol-water mixtures, one can use the melting-enthalpy AH obtained from DSC data. Note that in this specific case, the total melting-enthalpy (AH) was obtained by integration of the transition heat capacity (ACp) over the broad melting temperature interval ... 

Below 40 mol% of glycerol-water, domains appear. This critical concentration is related to the numbers of H-bonds of glycerol and of water respectively. DSC studies also confirm the same critical concentration. In water-rich mixtures, some water is frozen as a result, three relaxation processes where observed. These were related to ice-like structures, interfacial bound-water, and glycerol-water mixtures in the mesoscopic domains, where the concentration remains at 40 mol%. 

A series of manganese(II) chelates attached to polysaccharide molecules were synthesized and the Rj values were measured [72]. Ethylenediaminetetraacetic acid (Fig. 2) chelated to manganese(II) and attached to sucrose-epichlorohydrin copolymer and aminoethyldextran yielded Rj values of 19.2 mM s and 12.8 mM s , respectively, at 10 MHz and 37°C in a 1 2.13 glycerol-water mixture. Diethylenetriaminepentaacetic acid (Fig. 2) and triethylenetetraamine-hexaacetic acid (TTHA, Fig. 2) were both conjugated to dextran molecules. Chelating of manganese(II) ions resulted in complexes with Rj values at 10 MHz... 

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