Fusion curve

Likewise, the liquid-solid equilibria along the fusion curve is ... 

Fig. 2. PT diagram for a pure substance that expands on melting (not to scale). For a substance that contracts on melting, eg, water, the fusion curve. A, has a negative slope point / is a triple state point c is the gas—Hquid critical state (—) are phase boundaries representing states of two-phase equiUbrium ...

With liquids, the refractive index at a specified temperature and wavelength is a sensitive test of purity. Note however that this is sensitive to dissolved gases such as O2, N2 or CO2. Under favourable conditions, freezing curve studies are sensitive to impurity levels of as little as 0.(X)1 moles per cent. Analogous fusion curves or heat capacity measurements can be up to ten times as sensitive as this. With these exceptions, most of the above methods are rather insensitive, especially if the impurities and the substances in which they occur are chemically similar. In some cases, even an impurity comprising many parts per million of a sample may escape detection. 

Poynting (1881), from considerations based on equation (1) of 100, surmised that ice would melt, if the pressure on it is raised in such a way that any water produced flows away, under a pressure which is for a given temperature, only that on the fusion curve (i.e., when the water remains in contact with the... 

From the knowledge of the quantities (known by independent measurements) in Clausius-Clapeyron equation, the slope of the fusion curve can be evaluated and integrated to get pf(T). For example, in the 5-20 mK range, the Clausius-Clapeyron equation gave temperature values with an 1% accuracy [52,53] ... 

A Moving from point R to P we begin with H20(g) at high temperature (>100°C). When the temperature reaches the point on the vaporization curve, OC, water condenses at constant temperature (100°C). Once all of the water is in the liquid state, the temperature drops. When the temperature reaches the point on the fusion curve, OD, ice begins to form at constant temperature (0°C). Once all of the water has been converted to H20(s), the temperature of the sample decreases slightly until point P is reached. 

Since solids are not very compressible, very little change occurs until the pressure reaches the point on the fusion curve OD. Here, melting begins. A significant decrease in the volume occurs ( 10%) as ice is converted to liquid water. After melting, additional pressure produces very little change in volume because liquids are not very compressible. 

Walker, D., Agee, C. B. Zhang, Y. (1988). Fusion curve slope and crystal/liquid buoyancy. J. Geophys. Res., 93, 313-23. 

Temperature and pressure are the two variables that affect phase equilibria in a one-component system. The phase diagram in Figure 15.1 shows the equilibria between the solid, liquid, and vapour states of water where all three phases are in equilibrium at the triple point, 0.06 N/m2 and 273.3 K. The sublimation curve indicates the vapour pressure of ice, the vaporisation curve the vapour pressure of liquid water, and the fusion curve the effect of pressure on the melting point of ice. The fusion curve for ice is unusual in that, in most one component systems, increased pressure increases the melting point, whilst the opposite occurs here. 

A sublimation process is controlled primarily by the conditions under which phase equilibria occur in a single-component system, and the phase diagram of a simple one-component system is shown in Figure 15.30 where the sublimation curve is dependent on the vapour pressure of the solid, the vaporisation curve on the vapour pressure of the liquid, and the fusion curve on the effect of pressure on the melting point. The slopes of these three curves can be expressed quantitatively by the Clapeyron equation ... 

Fig. 28.—Fusion Curve of Mixtures of Perchloric Acid, HC104, and Water.

B. Karandeeff found that the fusion curves of the system KF—K2S04 gave eutectics at 883° (41 mols. per cent, of potassium fluoride), and 788° (83 mols. per... 

According to F. A. Fliickiger, lithium forms a basic carbonate lithium oxycar-bonate is a crystalline compound of lithium oxide and carbonate whose composition and limits of existence have not been explored. According to H. Ie Chatelier, the fusion curve of mixtures of potassium and lithium carbonates shows two eutectics, one at 5C0° and the other at 492°, corresponding respectively with 26 and 46 6 per cent, of lithium carbonate. The intermediate maximum at 515° corresponds with the formation of the double salt, lithium potassium carbonate, LiKC03. 

E. Groschuff studied the binary system NB4NO3—HNO3 over a range of temp. —10° to 70° and he prepared the solubility or fusion curves shown in Fig. 87. The solubility of ammonium nitrate in nitric acid is expressed in mols. of the salt in 100 mols. of nitric acid ... 

Flo. 87.—Fusion Curves of the Binary System, NH4NOa —HNOa. 

At very low temperatures carbon disulphide solidifies to a crystalline mass which melts at —112-97° C.7 The crystallisation may be accompanied by the emission of small sparks.8 At —185° C. the crystals are tetragonal.9 The heat of fusion, deduced from determinations of the freezing-points of dilute solutions in certain organic solvents,10 is 660 calories. The fusion curve showing the connection between pressure and melting-point has been determined.11... 

Figure 2.9 Phase diagram for C02, showing solid-gas (S + G, sublimation ), solid-liquid (S + L, fusion ), and liquid-gas (L + G, vaporization ) coexistence lines as PT boundaries of stable solid, liquid, or gaseous phases. The triple point (triangle), critical point (x), and selected 280K isotherm of Fig. 2.8 (circle) are marked for identification. Note that the fusion curve tilts slightly forward (with slope 75 atm K-1) and that the sublimation and vaporization curves meet with slightly discontinuous slopes (angle < 180°) at the triple point. The dotted and dashed half-circle shows two possible paths between a liquid (cross-hair square) and a gas (cross-hair circle) state, one discontinuous (dashed) crossing the coexistence line, the other continuous (dotted) encircling the critical point (see text).

The fusion curve of mixtures of arsenic and iodine shows no evidence of the formation of a pentiodide, but there is a eutectic, of freezing point 71-5° C., which has the approximate composition of this substance.5 The absorption spectrum of the solution in carbon disulphide is similar to that of a mixture of the triiodide and iodine.3... 

Fia. 71. —Fusion Curve of Mixtures of Nitrogen Peroxide and Nitric Oxide. 

E. Peligot said that after being melted, the peroxide requires a much lower temp, for its solidification, for at —16° the compound remains liquid, and J. Fritzsche said that it can be re-solidified only at —30° because a little nitric acid has been formed, and this also accounts for the turbidity of the cooling liquid. For the fusion curve with nitric oxide, vide supra, nitrogen trioxide. P. Pascal studied the f.p. of binary systems of nitrogen peroxide with bromoform, chloroform, carbon tetrachloride, bromobenzene, methyl iodide, chloropicrin, and camphor. 

Hernandez and Rutledge (1994) investigated, by low resolution pulse NMR, the evolution of solid fat content (SFC) at 27.5 °C of cocoa masses of various geographical origin. The ANOVA analysis of a few quantitative parameters correlated with solid content and the speed of its transition from decomposition of fusion curves which indicated that the... 

The curve O-B represents die conditions under which a solid and a liquid can coexist and called the fusion curve. ... 

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