Eutectic curve

Figure 12.2 Eutectic curves, (a) Sodium chloride in water, (b) Calcium chloride in water...

Figure 12.4 Propylene glycol in water, (a) Eutectic curve, (b) Density and specific heat capacity...

Eliminating first 8 2 and then ST from equations (22.24) we obtain, along the eutectic curve... 

This curve will, of course, lie in the plane formed by one face of the prism. In a similar manner we obtain the freezing-point curves Ak C and B gC. These curves give the composition of the binary liquid phases in equilibrium with one of the pure components, or, at the eutectic points, with a mixture of two solid components. If to the system represented say by the point ki, a small quantity of the third component, C, is added, the temperature at which the two solid phases A and B can exist in equilibrium with the liquid phase is lowered and this depression of the eutectic point is all the greater the larger the addition of C. In this way we obtain the curve which slopes inwards and downwards, and indicates the varying composition of the ternary liquid phase with which a mixture of solid A and B are in equilibrium. Similarly, the curves fegK and k K are the corresponding eutectic curves for A and C, and B and C in equilibrkim with ternary solutions. At the point K, the three solid components... 

It will be clear from the above discussion that if the ternary eutectic curves are projected on a plane parallel with the face BC of the prism, that is, if we express the composition of the solutions in accordance with the formula xA, yB, (100 ) C, then it will be possible to state, from the form of the curve obtained, whether or not the two components present in varying amount crystallise out pure or combine with each other to form a compound. It will be apparent that the projections of the ternary eutectic curves in the manner indicated, will yield a series of curves similar to the binary curves given in Figs. 33, 37, and 43, pp, 103, 109 and 119. 

The narrow triangular area lying between the areas for CaO and CagSiO (Fig. m) refers to the binary compound, CagSiO, which makes its appearance at 1900° on the eutectic curve for CaO and Ca2Si04. 

Compiler s comment It is not possible to construct a legitimate phase diagram on the basis of the data that are given. The cone, of component added has the meaning given to it only if the added component is a salt. When water is the added component, the relation Wjj = 100 - cone, of added component is valid. With this assumption the followiiig 2 compositions of points lying on the eutectic curve were calculated. 

A somewhat different method of plotting the results will help the reader to appreciate the significance of the eutectic temperature. In Fig. 1,11, 2 melting points are plotted against composition. The curve AC portrays the decreasing melting point of a-naphthol as naphthalene is added up to a mol fraction of 0 605. The curve BG represents the... 

Quantitative studies of solid-state organic reactions were performed by Glazman (267. 268). Equal amounts of acetic anhydride and 2-aminothiazole (grain diameter 0.15 mm) were mixed for 20 rain, and the mixture was heated in a glycerol bath at 0.5°C per minute. Heating curves showed that the reaction starts in the solid phase the use of an eutectic composition of organic reactants increases the yields. 

Salt Brines The typical curve of freezing point is shown in Fig. II-IIO. Brine of concentration x (water concentration is I-x) will not solidify at 0°C (freezing temperature for water, point A). When the temperature drops to B, the first ciystal of ice is formed. As the temperature decreases to C, ice ciystals continue to form and their mixture with the brine solution forms the slush. At the point C there will be part ice in the mixture /(/i+L), and liquid (brine) /i/(/i-t-L). At point D there is mixture of mi parts eutectic brine solution Di [concentration mi/(mi-t-mg)], and mo parts of ice [concentration mol m -t- mo)]. Coohng the mixture below D solidifies the entire solution at the eutectic temperature. Eutectic temperature is the lowest temperature that can be reached with no solidification. 

These relays also possess characteristics similar to those of a bimetallic relay and closely match the motor heating and cooling curves. They are basically made of a low-melting eutectic alloy which has defined melting properties. The alloy, with specific proportions of constituent metals such as tin, nickel and silver, can be made for different but specific melting temperatures. This property of the alloy is used in detecting the motor s operating conditions. 

Eutectic arrest In a cooling (or heating) curve an approximately exothermal segment corresponding to the time interval during which the heat of transformation from the liquid phase of two or more conjugate solid phases is being evolved (or conversely). 

Eutectic composition It has a minimum melting temperature when two or more liquid solubility curves interact. 

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