Supercooled solution

Still another situation is that of a supersaturated or supercooled solution, and straightforward modifications can be made in the preceding equations. Thus in Eq. IX-2, x now denotes the ratio of the actual solute activity to that of the saturated solution. In the case of a nonelectrolyte, x - S/Sq, where S denotes the concentration. Equation IX-13 now contains AH, the molar heat of solution. 

Several methods are employed to allow the observation of phosphorescence. One of the most common techniques is to supercool solutions to a rigid glass state, usually at the temperature of liquid nitrogen... 

As Vm2 is the molar volume of pure, supercooled solute. Equation (14.54) can be written as... 

Figure J. Possible pathways for stratospheric aerosol formation Left path the conventional 3-stage model ( SAT, NAT, [ice) the aerosol remains solid. Right path the aerosols remains liquid, takes up HNOj forming ternary supercooled solution, and freezes out below the frost point [15,28].

SDS/NaCI Mixtures. The effect of temperature on the micelles formed in 70 mM SDS + NaCl solutions is presented below. Mazer et al. (14) have found that the aggregation number, N, is at a maximum for supercooled solutions below the critical micellization temperature (cmt), and decreases towards the value expected for a spherical micelle as the temperature is increased. The variations in N with temperature are dependent on the concentration of added electrolyte, with the rodlike micelles formed in high salt (0.6 M) showing large variations, and the spherical micelles formed in little (0.3 M) or no salt showing only small variations. 

Figure 3.2 shows the mean square displacement (MSD) for water in the glassy and supercooled glucose solutions in a log-log scale. The most remarkable result is that water diffuses at 220 K, in the glass, as observed in the experiments. The diffusion at 220 K, however, occurs in a scale comparable with the /rs of the simulation and cannot be quantified from the data in Figure 3.2. For the five supercooled solutions, T = 250 to 365 K, we computed the diffusion coefficient from the long time dependence of...

Two types of rigid media have been employed in hyperfine studies supercooled liquid solutions or powders and single crystals. The anisotropy in the g and A tensors produces anisotropic line shapes in the ESR of supercooled solutions that can be analyzed to deduce the spin Hamiltonian parameters that will produce such shapes. In practice, line shapes... 

Transition Metal Complexes Attempts have been made to use the Fermi contact portion of the metal ion s hyperfine interaction to determine electron distribution in transition metal complexes, but these attempts have not been very successful or useful. Most of the useful data have been obtained from the anisotropic portion of the hyperfine constant as determined from single-crystal or supercooled solution studies. For ligand nuclei both the isotropic and anisotropic parts of the hyperfine interaction have yielded useful results on electron distribution. Although the most useful data still come from the anisotropic portion of the hyperfine interaction, there is need for more work in this area in that the available data are rather sparse for many important types of complexes. 

Further studies have shown that potentiation occurs only in supercooled solutions (32). In solutions with negligible supercooling, AFGP-8 has weak activity by itself, but in supercooled solutions its activity is expressed only in the presence of the larger, active AFGP-1 to AFGP-5. 

The antifreeze action of AFGP is different in many respects from the action of colligatively functioning substances or the effects found in supercooled solutions. 

You now have a supercooled solution of sodium acetate that can crystallize out of solution readily if a crystallization nucleus is present. 

It is well known that supercooled solutions without any nucleation control start their nucleation quite randomly so that, for the same cooling rates and the same experimental conditions, the nucleation temperatures are widely distributed. This behavior was observed by Nakagawa et al. (2006), as shown in Fig. 3.16 where the frequency distributions of experimental spontaneous nudeation temperatures are presented for mannitol, BSA and sucrose systems frozen at the same standard cooling rate, —1.0 K min. All plotted data were obtained under similar and rigorously controlled cooling conditions (cooling rates) and with glass vials (type, size, etc.) as clean and... 

On a mesoscale, crystallization firom supercooled solutions in poor solvents can lead to the formation of secondary structures, notably nanofibers, with a width of tens of nanometers and length of several micrometers [14]. 

The determination is made in the same manner as in the case of the benzene solutions (p. 133). It may, however, be found that crystallization commences with greater difficulty than in the case of benzene, so that, in order to prevent too great supercooling, it may be necessary to add a small crystal of ice to the supercooled solution. 

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