Solubility naphthalene

Dickhut, R. M., A. W. Andren, and D. E. Armstrong, Naphthalene solubility in selected organic solvent/water mixture , J. Chem. Eng. Data, 34,438-443 (1989). 

Lamb, D. M., Barbara, T. M. Jonas, J. NMR Study of Solid Naphthalene Solubilities in Supercritical Carbon Dioxide Near the Upper Critical End Point. J. Phys. Chem. 1986, 90, 4210M215. 

Figure lQis a graph of naphthalene solubility in carbon dioxide at 45 C (15 C above the critical temperature of carbon dioxide) taken from Reference 17. As is obvious from an examination of the data, the solubility of naphthalene increases dramatically when the pressure is increased beyond the critical pressure of 73 atm. The solubility (given in units of grams/liter in the reference) approaches about 10% (w/w) at a pressure level of 200 atm. 

Mole fraction of ethanol in the solute-free mixed solvent Mole fraction of naphthalene solubility Reference D... 

This large increase in the solvent power of ethylene on compression to 100 bar cannot be attributed to a hydrostatic pressure effect on the vapor pressure of naphthalene, since the pressure effect is explicitly accounted for in the exponential term in equation 1.1. Instead, the large difference in experimental and calculated naphthalene solubility at high pressures is associated with the nonideal behavior of ethylene as it is compressed to liquid-like densities in its critical region. It is the strength of the interactions between solvent and solute molecules that fixes the solubility depending of course on whether the solvent molecules are in close enough proximity to interact. Chapters 3 and 5 delve more deeply into intermolecular interactions and solubility behavior. 

When the third bst ce dissnlms m only one of the two liquids the mutual solubility of the latter is diminished, and the temperature at which the system becomes homogeneous is raised, in the case of liquids having an upper critical solution temperature, and lowered in the case of liquids having a lower critical solution temperature. The elevation (or the lowering) of temperature depends not only on the nature and amount of the added substance, but also on the composition of the liquid mixture. When the two liquids are present in the proportions of the critical composition, it is found that, for concentrations of the addendum (non-electrolyte) less than about 0 i molar, the elevation (or depression) of the critical solution temperature is nearly proportional to the amount added. The elevation (or depression) of the critical solution temperature for small equi-molecular quantities of different substances is, however, not constant, but depends on the nature of the substance added. In the following tables are given the values for the elevation of the critical solution temperature of phenol and water by naphthalene (soluble only in phenol) and by potassium chloride (soluble only in water). E represents the molecular elevation of the critical solution temperature —... 

Figure 12.1-1 The solubility of naphthalene in supercritical carbon dioxide as a function of pressure. The points and are the experimental data of McHugh and Paulaitis [7. Chem. Eng. Data, 25, 326 (1980)] at 7 = 35.0 and 60.4°C, respectively. The lines are the correlations of the data using the Peng-Rpbinsoti equation of state with kcoz-u = 0.103. Note the sharp increase in naphthalene solubility with pressure near the CO2 critic pressure of 73.76 bar.

The simplest type of phase behavior to understand is the solubility of a solid solute, such as naphthalene, in a supercritical fluid. When the solute is a crystalline solid, the solid phase may be assumed to be pure and only the supercritical phase is a mixture. Imagine solid naphthalene in a closed vessel under one atmosphere of carbon dioxide at 40°C. The reduced temperature and reduced density of CO2 are 1.03 and 3.7x10 respectively. At this pressure, the gas phase is ideal and the naphthalene solubility is determined by its vapor pressure. As the container volume is decreased isothermally, the solubility initially decreases when the gas phase is still nearly ideal. As the pressure is increased further, however, the gas phase density becomes increasingly nonideal and approaches the mixture critical density (near the critical density of CO2 because the gas phase is still mostly CO2). The reduced density of CO2 increases rapidly near the critical region as shown in Figure 2. The solvent power of CO2 is related to the density which leads to a rapid solubility increase. A brief description of intermolecular interactions is helpful in understanding this behavior. 

Figure 3. Naphthalene solubility in CO2 vs. temperature. (Reproduced with permission from Reference 11. Copyright 1986 Butterworth.)...

Eq. [5.5.53] is therefore conceptually sounder and physically more detailed than is eq. [5.5.23]. Eq. [5.5.53] shows, however, that in the absence of independent additional information (that is, information beyond that available from the solubility study alone) it is not possible to dissect the quantity (g2Y2A2 - giYiAj) into its separate terms. In some cases such additional information may be available, and here we discuss the example of naphthalene solubility in mixed aqueous-organic binary mixtures. Table 5.5.8 lists the values of gA(Y2-Yi) obtained by applying eq. [5.5.23] to solubility data in numerous mixed solvent systems. In an independent calculation, the solubility of naphthalene in water was written as eq. [5.5.55],... 

Table 5.5.8. Parameter estimates and derived quantities for naphthalene solubility in water-cosolvent mixtures at 25°C°...

Tjf = (T/Tc). The 12 "C (T = 1.01) isotherm of p vs. shows a rapid rise in p by more than an order of magnitude around Pr = 1.0. The shape of this curve is quite similar to that of the naphthalene solubility curve, suggesting that the solvent power of ethylene for naphthalene is directly related to the SCF solvent density near T Pc. 

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