Density water, supercooled

Liquid Water— Density—Compressibility — Viscosity — Vapour Pressure — Capillary Water—Supercooled Water—Thermal Conductivity—Specific Heat—Surface Tcnsmu—Electrical Conductivity—Spectrum— Colour. 

D.E. Hare and C.M. Sorensen, The density of supercooled water. II. Bulk samples cooled to the homogeneous nucleation limit, J. Chem. Phys., 87 (1987) 4840-4845. 

FIG. 5 The density of liquid and supercooled water as a function of temperature, illustrating the anomalous liquid phase density maximum of water (data from Lide, 2002-2003). 

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. 

Ludwig s (2001) review discusses water clusters and water cluster models. One of the water clusters discussed by Ludwig is the icosahedral cluster developed by Chaplin (1999). A fluctuating network of water molecules, with local icosahedral symmetry, was proposed by Chaplin (1999) it contains, when complete, 280 fully hydrogen-bonded water molecules. This structure allows explanation of a number of the anomalous properties of water, including its temperature-density and pressure-viscosity behaviors, the radial distribution pattern, the change in water properties on supercooling, and the solvation properties of ions, hydrophobic molecules, carbohydrates, and macromolecules (Chaplin, 1999, 2001, 2004). 

H20(as) can be decomposed into Gaussian subbands, it is found that the subband frequencies and intensites fall on the extrapolations of the respective temperature dependences of the Gaussian subbands fitted to the liquid Raman spectral contour (see Fig. B). This sample of H20(as) is almost certainly of the low density form, so the results are consistent with the assertion that low density H20(as) is closely related to supercooled water, a suggestion which is discussed in Sections VI and VII. 

Colorless gas mold-hke pungent odor melting point 6.45°C sublimes at 4.77°C supercools to a colorless liquid that boils at 4.5°C liquid density 2.8g/mL at 6°C soluble in water. 

Black crystaUine solid exists in two modifications stable black needles known as alpha form that produces ruby-red color in transmitted light, and a labile, metastable beta modification consisting of black platelets which appear brownish-red in transmitted light density of alpha form 3.86 g/cm at 0°C density of beta form 3.66 g/cm at 0°C alpha form melts at 27.3°C, vapor pressure being 28 torr at 25°C beta form melts at 13.9°C hquid iodine monochloride has bromine-hke reddish-brown color hquid density 3.10 g/mL at 29°C viscosity 1.21 centipoise at 35°C decomposes around 100°C supercools below its melting point polar solvent as a hquid it dissolves iodine, ammonium chloride and alkali metal chlorides hquid ICl also miscible with carbon tetrachloride, acetic acid and bromine the solid crystals dissolve in ethanol, ether, acetic acid and carbon disulfide solid ICl also dissolves in cone. HCl but decomposes in water or dilute HCl. 

White orthorhombic crystals in pure and anhydrous state or a clear, syrupy liquid melts at 42.35°C hygroscopic can be supercooled into a glass-like solid crystallizes to hemihydrate, H3PO4 I/2H2O on prolonged cooling of 88% solution hemihydrate melts at 29.32°C and loses water at 150°C density 1.834 g/cm3 at 18°C density of commercial H3PO4 (85%) 1.685 g/mL at 25°C pH of 0. IN aqueous solution 1.5 extremely soluble in water, 548 g/lOOmL at room temperature soluble in alcohol. 

The first way has been followed in what has become known as Car-Parrinello molecular dynamics (CPMD) (9). A solute and 60-90 solvent molecules are considered to represent the system, and the QM calculations are performed with density functionals, usually of generalised gradient approximation type (GGA), such as the Becke-Lee-Young-Parr (BLYP) (10) or the Perdew-Burke-Enzerhofer (PBE) (11,12) functionals. It is clear that the semiempirical character of concurrent density functional theory (DFT) methods and the use of these simple functionals imply a number of error sources and do not really provide a method-inherent control procedure to test the reliability of results. Recently it has been shown that these functionals even do not enable a correct description of the solvent water itself, as at ambient temperature they will describe water not as liquid but as supercooled system... 

In conclusion we have presented a model for an electronic complex system with coexistence of different electronic phases at critical densities and coexistence of different liquids described by the modified van der Waals model as proposed for supercooled water. We discuss the critical values of the anisotropic interactions for the spinodal lines. We find that this model is able to describe the evolution of the pseudo-gap temperature versus doping in different cuprate families. 

A. Khan. A liquid water model density variation from supercooled to superheated states, prediction of H-bonds and temperature limits. /. Phys. Chem., 104, 11268-11274, 2000. 

Physical Properties.— The crystalline acid was found to melt at 70-1° C.,5 74° C.6 The density of the liquid supercooled at 21° C. was 1-651.5 The latent heat of fusion of the acid was found to be 7-07 Cals.5 The heat of solution of the acid per mol dissolved in 400 mols or more of water was +233 Cals.5 The heat of formation of the crystallised acid has been given as +227-7 Cals.5... 

The aluminum derivative of ethyl acetoacetate is a white crystalHne material, reported to melt at 76°, or 78 to 79°. It supercools readily from the melt to a straw-colored, very viscous liquid. Molecular weight determinations in carbon disulfide indicate that the compound is not associated in that solvent. The aluminmn derivative of ethyl acetoacetate is very soluble in benzene, ether, and carbon disulfide. It is less soluble in petroleum ether or cyclohexane and is insoluble in water. The compound boils at 190 to 200° at 11 mm. The reported dipole moment, in benzene, is 3.96 Debye. Surface tension and density values for the liquid above the melting point have been reported by Robinson and Peak. ... 

Xie Y, Ludwig KF, Morales LG, Hare DE, Sorensen CM. Noncrit-ical behavior of density fluctuations in supercooled water. Phys. 

Some indirect experimental evidence exists for the liquid-liquid critical point hypothesis from the changing slope of the melting curves, which was observed for different ice polymorphs (30, 31). A more direct route to the deeply supercooled region, by confining water in nanopores to avoid crystallization, has been used more recently by experimentalists. These researchers applied neutron-scattering, dielectric, and NMR-relaxation measurements (32-35). These studies focus on the dynamic properties and will be discussed later. They indicate a continuous transition from the high to the low-density liquid at ambient pressure. The absence of a discontinuity in this case could be explained by a shift of the second critical point to positive pressures in the confinement. This finding correlated with simulations, which yield such a shift when water is confined in a hydrophilic nanopore (36). 

Although the presented scenarios are still under discussion, the existence of a first-order like transition between metastable high- and low-density supercooled water with a second critical point at negative pressures in bulk water and positive pressures in confinement is strongly suggested (29). Alternatively, singularity-free scenarios are discussed to explain the properties of supercooled water (24, 29). 

McLeroy. J. Chem. Phys. 21, 819-21 (1953). Ultrasonic velocity, density, and compressibility of supercooled water and D2O. 

Results relative to a 25% hydrated Vycor sample indicates that at room temperature interfacial water has a structure similar to that of bulk supercooled water at a temperature of about 0°C, which corresponds to a shift of about 25 K [40]. The structure of interfacial water is characterized by an increase of the long-range correlations, which corresponds to the building of the H-bond network as it appears in low-density amorphous ice [41 ]. There is no evidence of ice formation when the sample is cooled from room temperature down to -196°C (liquid nitrogen temperature). 

Moreover, in the case of the low level of hydration h = 0.25 the evolution of the density of states as a function of the temperature is less pronounced than in the case of h = 0.5. This is in agreement with the structural study [43] at the lower hydration (h = 0A 75), which only detected small changes when the temperature is lowered from room temperature to 77 K, and with further structural studies of low-hydrated Vycor samples. Low temperatures do not significantly affect the overall structure of the protein and the bound water molecule, and no crystallization of water has been observed. This could reflect the fact that at room temperature the interfacial water behaves like a dense supercooled liquid. 

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