Isothermal diagram

These isothermal diagrams can be used to consider the phase stability areas for more than one metal in contact with a common atmosphere and thus to assess the condensed phases which can be stable under the prevailing conditions. Figure 7.75 shows a stability diagram having phase areas for Co-S-O solid lines) and for Cu-S-O system broken lines). From this diagram it can be seen clearly that at 950 K at certain gas mixtures, pure metals Co and... 

There are fundamentally two types of gas adsorption processes, which can be differentiated by the way in which adsorbed species are desorbed. In one type the adsorbed species are removed by raising the temperature of the adsorbent, thereby decreasing its capacity. In the second type the partial pressures of the adsorbed species are reduced to effect desorption. Of course a combination of the two desorption techniques can be and is sometimes used. In Figure 1 an isotherm diagram is shown which depicts these desorption techniques. 

The effect of this extrapolation can be seen in isothermal diagrams. Figure 7.8 is the isothermal transformation diagram for a 1050 steel. Note that proeutectoid ferrite must form before cementite for transformation temperatures above about 600 °C in accordance with Figure 7.8. The agreement is not perfect because in addition to 0.50% C, the 1050 steel contains 0.91 % Mn, which lowers the eutectoid temperature and composition. 

Two dimensional isothermal diagrams which represent isothermal plane intersections with various surfaces (liquidus, solidus, etc). 

In order to solve this problem, the polythermal projection method was discussed in the previous section (Section 4.3.2). In this section, the other method, namely, two dimensional isothermal diagrams are discussed. 

Figure 7.1 Isotherm diagram illustrating pressure-swing (PSA) and temperatureswing (TS A) processes [5]. Reproduced with permission of the American Institute of Chemical Engineers. Copyright 1988, AIChE. All rights reserved.

The Isothermal Diagram.—For the representation of the isothermal relations in a ternary system, various methods can be employed. One may, in the first place, employ the triangular diagram, the use of which has already been explained (p. 204). Where we are dealing with the equilibria between aqueous solutions and two salts with the same ion, a simple two-branched curve, ach (Fig. 116), will be obtained if the two salts do not form any double salt. In this diagram, a represents the solubility of the salt A, h the solubility of the salt B, while the curves ac and he represent ternary solutions in equilibrium with solid salt A and solid salt B respectively. At c we have an invariant system in which the solution is in equilibrium with both salts as solid phases. 

When the two components, A and B, can form a compound, the isothermal diagram will exhibit three curves, such as ac, cc c b (Fig. 117), c and representing solutions which are in equilibrium with pure A and double salt, and pure B and double salt respectively. The composition of the anhydrous double salt is represented by the point D on the side of the triangle AB. 

From the information yielded by the isothermal diagrams based on the solubility data, it is possible to decide the conditions under which potassium nitrate can best be prepared by double decomposition between potassium chloride and sodium nitrate. Thus Reinders has... 

Under the conditions of experiment (temperature = 15 ) sodium chloride and ammonium bicarbonate cannot coexist in contact with solution. These determinations gave the data necessary for the construction of the complete isothermal diagram (Fig. 153). For the sake of comparison, the results are also represented in the quadrangular diagram of Janecke (Fig. 154). The most important of these data are given in the following table (temperature 15 ) —... 

Figure 7.2. Isotherm diagram for carbon dioxide. Broken lines indicate crossing of isotherms at either constant pressure or density.

Fig. 55.—Isothermal Diagram for the System PhSOj-f-KjCrOj K SOj -f-PbCrO. ...

Fig. 56.—Isothermal Diagram for the System PbCOa-f-KaCrOi KjCOj -f-PbCrOi.

Sections 2.5.3 and 3.6.4 introduce and discuss the properties of isotherm plots. Each isotherm represents all combinations of compositions that have equivalent boiling temperatures. For ideal systems these isotherms are linear, while nonideal systems are somewhat curved. An isotherm diagram for the nonideal acetone/methanol/ethanol system smdied above is shown in Figure 4.19. 

Ternary systems comprising water and two electrolytes containing a common ion often yield solid solutions. Such a system can be represented in the manner indicated in Figure 4.26 an isothermal diagram for salts A and B and solvent water W. Points a and b represent the solubilities of salts A and B at the given... 

Figure 9.2 7 A binary A H- BC system treated as ternary (hypothetical isothermal diagram). Component B is the mesomorphic component in the semirigid copolymer BC. The compositions along the axis are measured in molar fractions x. (According to [II] with permission of Elsevier Science Publ.)...

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