Supercooled Aqueous Solutions Research Articles

The charge transfer to solvent spectrum of iodide in supercooled water and glass-forming aqueous solutions

The charge transfer to solvent spectrum of iodide in supercooled water and glass-forming aqueous solutions

Density of supercooled aqueous solutions of alcohols

1. The specific volumes of aqueous solutions of three alcohols were determined at the temperatures 0 to −40°. 2. The dependences of the specific volumes on the concentration of solutions of isopropyl and tert-butyl alcohols at temperatures below −20° have a maximum and a minimum. 3. For most aqueous solutions at temperatures below 4°, the difference between the specific volume of pure water and its partial specific volume in solution increases with decreasing temperature. 4. For solutions of isopropyl and tert-butyl alcohols in a limited range of concentrations and temperatures, the opposite effect is observed.

Ice Nucleation in a Venus Atmosphere

Abstract The possible phase of Venus cloud particles has been experimentally studied. Carbon dioxide gas of 0.83 atm held in a uniform temperature mixing cloud chamber was used as a simulated Venus atmosphere at the condensation level. The ice nucleating behavior of some artificial and natural ice nuclei were tested. The heterogenous and homogeneous ice nucleation temperatures in the CO2 atmosphere were found to be 0.5–1.0C lower than those in air. The formed ice crystals showed no appreciable difference in comparison with those found in air. The results indicated that at temperatures < −38.5C the condensate in Venus atmosphere is likely to be ice crystals and above that temperature it can be either supercooled aqueous CO2 solution or ice crystals, depending on the availability of natural ice nuclei.

The growth of ice parallel to the basal plane in supercooled water and supercooled metal fluoride solutions

The growth rates of ice dendrites in pure water and in 10 -2 molar aqueous solutions of LiF, NaF, KF, and AlF 3 have been measured for supercoolings ranging from 0.1 °C to 2.5 °C. In this range of supercoolings the ice crystals are dendritic and grow parallel to the basal plane. The experiments in pure water show that the radius of curvature of the tip decreases with increasing supercooling and that the growth rate varies periodically about the average growth rate. The experiments indicate that the enhancement of the growth rate of ice dendrites in supercooled aqueous metal fluoride solutions is due to the preferential orientation of the water molecules by the interface freezing potential.

Synthetic polynucleotides in fluid supercooled aqueous alcohol solutions

The effects of variation of solvent parameters, such as viscosity and dielectric constant (as a function of temperature), on the absorption spectra of synthetic polynucleotides in fluid-supercooled aqueous alcohol solvents were examined. The presence of a weak acid, the dissociation of which depends on the temperature, can lead to controlled protonation of certain polymers.

The growth of ice in supercooled aqueous solutions

Growth rates parallel to and normal to the basal plane have been determined for ice growing in 10 -1 molar aqueous solutions of KF and CsF and 10 -3, 10 -2 and 10 -1 molar aqueous solutions of LiI, supercooled by up to 6°C. In all solutions, except the 10 -3 molar LiI, the growth rate normal to the basal plane is higher than that in pure water; in 10 -3 molar LiI it is unaffected. In the KF, CsF solutions the growth rate parallel to the basal plane is higher than that in pure water while in 10 -2 and 10 -3 molar LiI solutions it is unaffected and in 10 -1 molar LiI it is reduced.

On the electrical effects that accompany the spontaneous growth of ice in supercooled aqueous solutions

Measurements revealed that the spontaneous growth of ice crystals in supercooled aqueous solutions is accompanied by electrical effects. These effects were investigated at supercoolings between 2° and 11°C and in various salt solutions with salt concentrations between 10−6 and 10−1 mole liter−1. Freezing potentials up to 15 volts and freezing currents as large as 0.1 μamp were observed. The magnitude of the freezing potentials varied only slightly with the growth rate of ice but varied strongly and systematically with the concentration of salt in solution, with the type of salt dissolved, and with the time elapsed after freezing was initiated. The variation of the freezing potential with time was characterized by a sharp rise of the freezing potential in the very initial stages of ice growth and by a subsequent slower decay, which depended on the type of solution. In solutions with salt concentration larger than 10−1 mole liter−1 or smaller than 10−6 mole liter−1, the freezing potential was negligibly small. Maximum potentials developed in solutions with concentrations between 10−5 and 10−3 mole liter−1. By comparing solutions of salts with a common anion, it was found that the freezing potentials varied only slightly with the type of cation. By comparing solutions of salts with a common cation, it was found that the freezing potential varied markedly with the type of anion and was largest in fluoride solutions and smallest in iodide solutions. Ammonium solutions developed freezing potentials with a sign opposite to that developed in alkali halide solutions. It was shown that the magnitude of the freezing potentials is directly correlated to the electronegativity of the elements in solution. A comparison is drawn between the electrical effects observed during the spontaneous freezing of aqueous solutions and the electrical effects that develop when ice grows in aqueous solutions at a rate that is about 104 times smaller, as is the case in a Workman-Reynolds type experiment. Some speculations are given about the significance of the observed electrical effects to thunderstorm electricity.

Growth velocities of ice in supercooled water and aqueous sucrose solutions

Abstract Measurements have been made of the component velocities parallel to and normal to the basal plane of ice growing in supercooled water and aqueous sucrose solutions at supercoolings up to 10°C. It has been found that there are discontinuities in the velocity curves for the sucrose solutions. It is inferred that these are due to a growth mechanism change.

Über die kristallisation von eis aus salzlösungen

In a supercooled aqueous solution of sodium chloride, growing ice has the shape of needles or dendrites. It is difficult to separate the pure ice crystals from the adherent brine. If a layer of ice is deposited on cool walls, it will grow up opaque as it is filled with small inclusions of brine. Under Special conditions, however, a film of clear ice grows up which does not include any brine. It is shown that a relationship exists from which the maximum growing rate for clear ice can be derived.

Some relations between the structure of the ice-solution interface and the free growth rate of ice crystals in supercooled aqueous solutions

An experimental method was devised to determine the rate at which ice crystals grow freely in supercooled water and in dilute aqueous solutions of various salts. The solutions had concentrations between 10 −5 and 10 −1 moles liter −1 and were investigated at bath supercoolings between 0.5° and 20°C. It was found that the growth rate of ice crystals varied approximately with the square of the bath supercooling. Dissolved salts affected the growth rate of ice crystals in a systematic manner. At concentrations larger than 10 −2 moles liter −1 all salts reduced the growth rate below the one in pure water by an amount which depended on the type of salt in solution. At concentrations smaller than 10 −2 moles liter −1 some salts did not affect the growth rate whereas others increased it over and above the one in pure water. It was concluded that at low solute concentration the growth rate of ice in aqueous solutions is limited by the rate of dissipation of latent heat. As the solute concentration increases, the rate of diffusion of solute atoms away from the interface becomes increasingly important. At concentrations larger than 10 −2 moles liter −1 the growth rate reflects in a systematic manner the freezing point lowering effects associated with the poor mass transfer conditions which prevail in a stagnant system. Some of the observations are discussed in terms of the effect of the dissolved salts on the growth kinetics.

On the growth of ice crystals in supercooled water and aqueous solution drops

The results of a recent investigation on the free growth rate and the growth forms of ice in supercooled water and aqueous solutions are presented. The results are used to discuss the structure of frozen drops, the structure of hailstones, the mechanisms which are responsible for the glaciation of atmospheric clouds and the mechanisms which cause cloud electrification. It was found that the presence of dissolved salts and dust particles in cloud drops favor the formation of spongy and polycristalline ice, that it is unlikely for frozen cloud drops to develop into hexagonal shaped ice single-crystals, and that it is also unlikely that in atmospheric clouds freezing drops shatter and splinter. The latter result casts serious doubts on the splintering mechanism to contribute to thunderstorm electrification and to promote glaciation of clouds.

Growth Modes of Ice Crystals in Supercooled Water and Aqueous Solutions

The growth modes of ice crystals in supercooled water and various aqueous solutions were studied at different supercoolings by a motion-picture technique. ln pure water contained in plastic capillary tubes, ice dendrites formed which at supercoolings between 1 and 4°C. grew parallel to the tube axis. At supercoolings larger than 4°C. the direction of growth was inclined to the tube axis such that the dendrites hit the tube wall and afterwards proceeded growing in a new direction. As a result it appeared that the ice crystals grew in a zig-zag or screw fashion. This growth mode became enhanced when the supercooling was increased or salts were dissolved in the water. In large water drops, ice dendrites formed which at supercoolings smaller than 1°C. were co-planar with the seed crystal and between 1° and 5°C. split into two dendritic segments. At supercoolings larger than 5°C. multiple splitting of the seed crystal was observed and this became strongly enhanced when salts were dissolved in the water. Tentative explanations for these results are given.

Growth Modes of Ice Crystals in Supercooled Water and Aqueous Solutions

The growth modes of ice crystals in supercooled water and various aqueous solutions were studied at different supercoolings by a motion-picture technique. ln pure water contained in plastic capillary tubes, ice dendrites formed which at supercoolings between 1 and 4°C. grew parallel to the tube axis. At supercoolings larger than 4°C. the direction of growth was inclined to the tube axis such that the dendrites hit the tube wall and afterwards proceeded growing in a new direction. As a result it appeared that the ice crystals grew in a zig-zag or screw fashion. This growth mode became enhanced when the supercooling was increased or salts were dissolved in the water. In large water drops, ice dendrites formed which at supercoolings smaller than 1°C. were co-planar with the seed crystal and between 1° and 5°C. split into two dendritic segments. At supercoolings larger than 5°C. multiple splitting of the seed crystal was observed and this became strongly enhanced when salts were dissolved in the water. Tentative explanations for these results are given.

Morphology of Ice Dendrites

The morphology of ice crystals produced in supercooled aqueous solutions is described. A freely growing ice dendrite in distilled water propagates in the 〈112̄0〉 direction and has the shape of a very thin flat sheet. The first examples of dendrites which grow in an irrational crystallographic direction, best described as 〈112̄Z〉, have been produced in aqueous solutions. The value of Z has been found to vary between 0 and 0.35, depending upon amount of supercooling, the solute, and solute concentration. Growth of ice upon a substrate is of a very complex nature with numerous grain boundaries and a varying orientation relative to the substrate.

Habits of ice grown in supercooled water and aqueous solutions

Abstract At small supercoolings the direction of growth of ice in pure water and aqueous solutions is parallel to the basal plane. As the supercooling is increased the growth direction of the dendrites become inclined at an angle to the basal plane, the angle increasing with supercooling. The most general habit of growth now has the form of two symmetrically situated hollow hexagonal pyramids joined at their apices. At still larger supercoolings further growth ensues from the initial dendrites comprising the pyramidal segments and complex three-dimensional structures are produced which are nevertheless single crystals. It is noted that the pyramidal growth habit occurs also in ice crystals formed from the vapour phase at high supersaturations and in Tyndall figures produced in the melting of ice. The non-rational growth of the dendrites is explained in terms of deposition predominantly on basal surfaces on one side of the dendrite tip and on prism faces on the other, the direction of growth being determin...