Quintuple-point

As a result the situation at the quintuple point must approximately be that shown in Fig. 8. In the four-phase line HnL Lfi there... 

CH4-C3H8-H20 does not end in a quintuple point but proceeds to high pressures until two phases (Lx and G) become critically identical. This arises from the fact that the critical temperature of methane is below room temperature (cf. Section III.C.(l)). 

Two quintuple points (Qi and Q2) fix the positions of the lines in Figure 4.4. Each point (Qi and Q2) is the origin of five four-phase lines. However, only the two lines of central importance (discussed below) have been measured from each quintuple point. 

The lower quintuple point (Qi) is the location of five coexisting phases—namely, I-Lw-sH-V-Lhc- The position of Qi is determined by the intersection of the I-sH-V-Lhc fine and the Lw-sH-V-Lhc line, close to the ice point temperature (273.15 K). However, the pressure of Qi is a function of the hydrate guests. 

The upper quintuple point (Q2) has a common line with Qi (Lw-sH-V-Lhc)> but it also is the origin of a new line (Lw-sI-V-Lhc) At temperatures higher than Q2 the hydrate phase is si rather than sH. 

Three quintuple points in this system have been determined by Bassett 4 as follows —5... 

For the ternary water-phenol-carbon dioxide system, several interesting phenomena were observed. As shown in Figure 2, the four-phase, water-rich liquid-phenol-rich liquid-phenol clathrate-vapor (Lw-Lp-C-V), dissociation pressures were measured at several temperatures near 293.0 K. Like above the phenol-carbon dioxide clathrate equilibrium results, the dramatic increase of the four-phase dissociation pressures was observed in a vicinity of 293.0 K. One of the most interesting results observed in this work is that a quintuple point at which the five phases of water-rich liquid, phenol-rich liquid, carbon dioxide-rich liquid, phenol clathrate, and vapor coexist in equilibrium was carefully measured and found to be 293.7 K and 57.2 bar. 

Quintuple points.—We may go farther in a system formed of three independent components, susceptible of having five phases, a quintuple point will be met, where the five curves of transformation will cut which correspond to the five monovariant S3rstems obtained by excluding successively one of the five phases this quintuple point is a transition point. 

Here are two examples of quintuple points analyzed by Bakhuis Roozboom ... 

The temperature, 0 22P, is that of the quintuple point 3 in tlie neighborhood of this point the five curves of transformation are arranged as is shown in Fig. 61. 

Ciystals Cj of hydrated cupric acetate Cu(CjH30j) Hj0 4 . Crystals C3 of hydrated calcic acetate Ca(C2H303) H30 6 . Crystals D of cupri-calcic acetate CuCa(CJ3,02)3 6H30. The temperature 76 is the temperature of a quintuple point 3 in the neighborhood of this point the five curves of transformation tensions are arranged as shown in Fig. 52. 

QuaDRIVARIANT ST8TBBIS, 130 Quadruple point, 192 Quintivariant system, 140 Quintuple point, 193... 

The triple point considered as transition point, 189.—xOo. Generalizations of the preceding ideas. Quadruple points, 192.—x6x. Quadruple points in the study of hydrates from a gas, 198.—x6a. Quintuple points, 193. 

Vapour Pressure. Quintuple Point.—In the case of Glauber s salt, we saw that at a certain temperature the vapour pressure curve of the hydrated salt cuts that of the saturated solution of anhydrous sodium sulphate. That point, it will be remembered, is a quadruple point at which the four phases sodium sulphate decahydrate, anhydrous sodium sulphate, solution, and vapour, can coexist and is also the point of intersection of the curves for four univariant systems. In the case of the formation of double salts, similar relationships are met with and also certain differences, due to the fact that we are now dealing with systems of three components. Two cases will be chosen here for brief description, one in which formation, the other in which decomposition of the double salt occurs with rise of temperature. 

This constitutes, therefore, a quintuple point and since there are three components present in five phases, the system is invariant. This point, also, will be the point of intersection of curves for five univariant systems, which, in this case, must each be composed of four phases. These systems are —... 

Transition Point.—In the case of the formation of double salts from two single salts, we saw that there was a point—the quintuple point—at which five phases could coexist. This point we also saw to be a transition point, on one side of which the double salt, on the other side the two single salts in contact with solution, were found to be the stable system. A similar behaviour is found in the case of reciprocal sal -pairs. The four-component system, two reciprocal salt-pairs and water, can give rise to an invariant system in which the six phases, four salts, solution, vapour, can coexist the temperature at which this is possible constitutes a sextuple point. This sextuple point is also a transition point, on the one side of which the one salt-pair, on the other side the reciprocal salt-pair, is stable in contact with solution. 

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