Freeze melting curves

Two other types of equilibrium curves are occasionally encountered with the system of two components forming a continuous series of solid solutions. These are shown in Figs. 1,16, 3 and 1,16, 4. In the former the freezing or melting curve passes through a minimum (examples p-chloroiodobenzene, m.p. 57° - p-dichlorobenzene, m.p. 53° naphtha-... 

J. C. Randall, Phillips Petroleum, Oklahoma I was interested in your linewidth curves vs temperature in which you essentially had the melting point curves. Did you do any freezing point curves ... 

The normal freezing point of the liquid under pressure is given by Tp, and OS is the melting curve of the substance, i.e. the locus of the points defining the co-existence of solid and liquid. If we measure the freezing point of a liquid in a closed system, the Phase Rule tells us that since at that temperature all three phases will be in equilibrium, F=0, and we obtain the... 

Cadmium Arsenides.—The freezing point, density and atomic volume curves indicate the existence of two arsenides, Cd3As2and CdAs2.n The freezing point curve was obtained by cooling mixtures of the elements melted under fused alkali chloride no mixed crystals were observed. Two other arsenides have been described Cd6As, said to... 

Cryoscopic and ebullioscopic measurements indicate that the halides of phosphorus, arsenic, antimony, titanium and tin readily undergo reciprocal interaction with interchange of halogen atoms and that mixed halides can be formed11 (see p. 103). Melting and freezing point curves are, however, generally of the eutectic or mixed crystal types, without... 

A study of the freezing-point curve of solutions of hydrogen peroxide in water indicates the existence of a definite hydrate H202.2H20, melting at —51° C.1... 

With lead the freezing-point curve exhibits two maxima, namely, at 454° C. and 1219° C., corresponding to the compositions PdPb2 and Pd3Pb, respectively. Three breaks occur at 495°, 596°, and 830° C. respectively. The first and last, namely, at 495° and at 830° C., indicate the existence of the compounds PdPb and Pd2Pb, and which decompose below their melting-points. It is not yet certain what the composition of the alloy represented by the break at 596° C. may be.4... 

Copper.—With copper, platinum yields a series of very tenacious alloys. Those containing over 40 per cent, of platinum are white. The freezing-point curve of the alloys, containing from 80 to 100 per cent, of copper, falls continuously to the melting-point of copper. The metals yield a continuous series of mixed crystals.6... 

Cu3P is a crystalline steel-grey or silvery-white substance which is harder than wrought iron. The melting-point is about 1018° C. and is lowered by additions of copper, as that of pure copper is by small additions of phosphorus the Cu-Cu3P freezing-point curves meet at a eutectic which corresponds to 8-2 per cent, of phosphorus with a freezing-point of 707° C.1... 

Iron-chromium alloys, free from carbon, may be prepared from chromite by the alumino-thermic method. From a study of the cooling-and freezing-point curves it has been suggested that a compound, Cr Fe, exists, but this is questioned by Janecke, who studied the iron-chromium system by means of fusion curves and by the microscopic study of polished sections of various alloys between the limits 10 Fe 90 Cr and 90 Fe 10 Cr, and came to the conclusion that the system consists of a single eutectic which can form mixed crystals with either component. The eutectic contains 75 per cent, of chromium and melts at 1320° C. The addition of chromium to iron increases the readiness of attack by hydrochloric and sulphuric acids, but towards concentrated nitric acid the alloys are rendered passive. They remain bright in air and in water. The presence of carbon increases the resistance to acids and renders them very hard if carbon-free, they are softer than cast iron. All the alloys up to 80 per cent, chromium are magnetic. Molybdenum, titanium, vanadium, and tungsten improve the mechanical properties and increase the resistance to acids. 

Fig. 23.8 gives the freezing point curve of the system cZ-+ dimethyl tartrate, which has a maximum at the melting point of the racemic compound. To test equation (23.20), log o 2(1 -X2) is plotted against 1/T in fig. 23.9. A straight line is obtained, whose slope gives for the latent heat a value of about 10500 cal./mole. 

This discussion of addition compounds covers only those compounds which are completely dissociated on melting, and the change in shape of the freezing point curve near a maximum is attributed to deviations of the liquid phase from ideality ( 5). In many instances there is good evidence that addition compounds exist also in the hquid phase when this occurs the curvature of the freezing point curve near the maximum is related to the equilibrium constant for the dissociation of the addition compound in the hquid. One example of this behaviour which has... 

FIGURE 8.11 State diagram for food materials, showing the Tg curve and isoviscous states above Tg. Maximally freeze-concentrated solids with a solute concentration of C g have Tg at T g. Ice melting within maximally freeze-concentrated materials occurs at T m. The equilibrium melting curve shows the equilibrium melting point Tm as a function of concentration. (From Roos, Y.H. and Karel, M., Food Technol., 45, 66, 1991b.)... 

The line separating the solid and liquid phases is known as the melting or freezing curve. The line separating the solid and vapor phases is known as the sublimation curve. The point where the vapor pressure curve, the melting curve, and the sublimation curves meet is the triple point. At these conditions, the solid, liquid, and vapor phases can simultaneously coexist. 

Values of Water Content (wtot), Enthalpy, T nseu peak and Unfrozen Water Content (UFW) from Ice Melting Curves, After Freeze Cycle on DSC, of Dough According to Formulation... 

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