Metastable ice

Balagurov, A.M., Barkalov, O.I., Kolesnikov, A.I., Mironova, G.M., Ponytovsky, E.G., Sinitsyn, V.V., et al. (1991) Neutron-diffraction study of phase transitions of high-pressure metastable ice VIII, JETP Lett. 53(1), 30-34. 

Figure 1 The phase diagram of ice, including liquidus lines of metastable ices IV and...

If, however, the behaviour of metastable Ice III is studied to very much lower temperatures, using low-frequency dielectric measurements which are a sensitive indicator of proton disorder, a transition to an ordered state of low dielectric constant is found at about -100 °C (Whalley et al. 1968), the ordered phase having been named Ice IX. The oxygen positions in Ice IX are apparently the same as those in Ice III and there is very little volume change in the III IX transition, as indicated by its horizontal equilibrium line. The static dielectric constant of Ice III falls steadily as the transition temperature is approached, which suggests that the proton ordering is antiferroelectric in nature. 

Professor Martin Chaplin of London South Beach University maintains a website on the properties of water, incuding metastable ice IV. Since the web address of the site can change, the site is best accessed by searching for Professor Chaplin s name. 

Figure 14.9 Partial phase diagram for ice (metastable equilibrium shown by broken lines).

Ice I is one of at least nine polymorphic forms of ice. Ices II to VII are crystalline modifications of various types, formed at high pressures ice VIII is a low-temperature modification of ice VII. Many of these polymorphs exist metastably at liquid nitrogen temperature and atmospheric pressure, and hence it has been possible to study their structures without undue difficulty. In addition to these crystalline polymorphs, so-called vitreous ice has been found within the low-temperature field of ice I. It is not a polymorph, however, since it is a glass, i.e. a highly supercooled liquid. It is formed when water vapour condenses on surfaces cooled to below — 160°C. 

Careful cooling of pure water at atmospheric pressure can result in water that is able to remain liquid to at least 38 °C below its normal freezing point (0 °C) without crystallizing. This supercooled water is metastable and will crystallize rapidly upon being disturbed. The lower the temperature of the supercooled water, the more likely that ice will nucleate. Bulk water can be supercooled to about — 38 °C (Ball, 2001 Chaplin, 2004). By increasing the pressure to about 210 MPa, liquid water may be supercooled to — 92 °C (Chaplin, 2004). A second critical point (C ) has been hypothesized (Tc = 220 K and Pc = 100 MPa), below which the supercooled liquid phase separates into two distinct liquid phases a low-density liquid (LDL) phase and a high-density liquid (HDL) phase (Mishima and Stanley, 1998 Poole et al., 1992 Stanley et al., 2000). Water near the hypothesized second critical point is a fluctuating mixture of LDL and HDL phases. 

The precise determination of the composition of individual fluid inclusions in the H20-NaCI-(Ca,Mg)Cl2 system from low temperature microthermometry is often limited by the difficulties in observing the melting of salt hydrates and by their common metastable behaviour. To add, the liquid phase can fail to nucleate any ice or hydrate during cooling down to -190°C. 

Schluter, 0.,Urrutia-Benet, G. U., Heinz, V., Knorr,D. (2004). Metastable states of water and ice during pressure-supported freezing of potato tissue. Biotechnol. Progress, 20, 799-810. 

If ice-cream is warmed or the temperature fluctuates, some ice will melt, and an infinite variety of lactose concentrations will emerge, some of which will be in the labile zone where spontaneous crystallization occurs while others will be in the metastable zone where crystallization can occur if suitable nuclei, e.g. lactose crystals, are present. At the low temperature, crystallization pressure is low and extensive crystallization usually does not occur. However, the nuclei formed act as seed for further crystallization... 

Vapour pressures for a number of atmospherically relevant condensed systems have been measured with mass spectrometry. These systems include hydrates of HC1, HjS04 and HNO, supercooled liquids and pure water-ice, as well as the interactions of HC1 vapour with die solids, ice and NAT [23,47,50-55]. Vapour pressure measurements over HNOj/HjO hydrates have also been made using infrared optical absorption with light originating from a tunable diode laser [29]. This technique allowed the identification of the metastable NAD in presence of the more stable NAT under temperature and vapour pressure conditions near to those found in the polar stratosphere. Vapour pressures of Up, HN03, HC1, HBr over supercooled aqueous mixtures with sulfuric acid have been calculated using an activity model [56]. It provides a parameterized model for vapour pressures over the stratospheric relevant temperatures (185-235 K). 

The ice generator consists of two vertically assembled 5-foot sections of 6-inch borosilicate glass pipe. The refrigerant and brine mixture jets toward the wall near the top of the column. The refrigerant flashes off immediately, leaving the ice slurry to slide down the walls. A large wall area is provided to allow time for the small amount of methylene chloride hydrate which forms to decompose. Although metastable at the column pressure, the hydrate which does form decomposes slowly. At the bottom of... 

Metastability with respect to ice crystal formation was not apparent in this freezer, probably because particulate matter in the salt solution induced nucleation. Nevertheless, more ice may be produced for a given pressure difference and surface when the slurry is recycled. The ice in the flowing slurry presents more surface and precludes the necessity of high driving forces to induce nucleation. Also, the size of the ice crystals is increased by recycle of slurry. 

Forms of ice designated as IV, IX, X, and XI have also been reported in the literature. See P. W. Hobbs, Ice Physics, Clarendon Press, Oxford, 1974, pp. 60-67 and C. Lobban, J. L. Finney, and W. F. Kuhs, The Structure of a New Phase of Ice , Nature, 391, 268-270 (1998). These phases are not shown in Figure 13.7, since they are metastable, not yet well-defined, or occur at pressure and temperature extremes beyond those given in the figure. 

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