Surface tension molal

The surface tension of an aqueous solution containing an organic solvent (or salt) is a function of the molal solvent (or salt) concentration, m, and can be given by... 

The surface tension of the aqueous solution of dode-cylaitunonium chloride (DAC) — decylairanonium chloride (DeAC) mixture was measured as a function of the total molality m of surfactants and the mole fraction X of DeAC in the total surfactant in the neighborhood of the critical micelle concentration (CMC). By use of the thermodynamic equations derived previously, the mole fraction in the mixed adsorbed film was evaluated from the y vs. X and m vs. X curves. Further, the mole fraction in the mixed micelle was evaluated from the CMC vs. X curve. By comparing these values at the CMC, it was concluded that the behavior of DAC and DeAC molecules in the mixed micelle is fairly similar to that in the mixed adsorbed film. 

Figure 2. Surface tension vs. composition curves at constant total molality 1, m = 6 mmol kg l 2, 8 mmol kg 3, 10 mmol kg 4, 12 mmol kg 5, 14 mmol kg" 6, 20 mmol kg 7, 30 mmol kg ...

Table I. Relative Effectiveness of Various Ions in Stabiliiinq the Native" Form of Collaqen and Ribonuclease <61 and the Predicted Relative Order Using the Molal Surface Tension Increment (7)...

The combination of the hydrophobic salting out and the electrostatic salting in terms explains very nicely the Class I type behavior. The data for carboxyhemoglobin and fibrinogen are well fitted by the theory (Figure 10). Also the order of decreasing molal surface tension increment generally follows the lyotropic order (7). 

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

TABLE 6 Characteristic Molal Surface Tension Increments of Different Salts Used in HP-HIC... 

Salt Molal surface tension increment a X IO]dyne g cm" 1 mole - 1... 

Figure 3.73. Surface tension change caused by potassium salts (a) and the corresponding acids (b) m is the molality and the osmotic coefficient. (Redrawn from J.E.B. Randles. Phys. Chem. Uq. 7 (1977) 107.)...

Van Hook and Phillips (34) and Van Hook (37) have discussed the application of Equation 1 to gas-liquid and gas-solid chromatography respectively. First consider the corrective terms. The third term in Equation 1 corrects for the isotope effect on the partial molal volumes of the condensed phase. In the case of the two dimensional adsorbed film the term should be rewritten in terms of the surface tension and the molar coverage. In either event the correction is expected to be of the same order of magnitude as that for the pure liquids (where it reduces simply to the isotope effect on molar volumes). These corrections are negligibly small. They amount to only about 0.1% of the total isotope effect per D atom for representative hydrocarbons (35). Similarly, the fourth term which corrects for the isotope effect on the nonideality of the gas phase is readily shown to be negligibly small (31, 35) under normal chromatographic conditions. 

Figure 6.5 Surface tension, y, as a function of log molal concentration at 30°C showing the increase of hydrophobicily associated with a Br substituent on the phenyl ring of an antihistamine.

It is shown 30) that the analysis of a relationship between the salting-out constants of a given protein and the molal surface tension increments makes it possible to estimate the relative surface hydrophobicity which is calculated as the ratio of the nonpolar surface area to the molecular weight of the protein. According to the concept developed by Melander et al 30), the hydrophobic character of a protein is believed to be constant at both high and physiological concentrations of different inorganic salts, which seems to be untrue in most cases (see below). 

Plot y versus In m and determine the surface excess of acetic acid using the Gibbs adsorption isotherm. (Note We can use the molality, m, in the isotherm instead of C2, the molarity.) b) At 25 °C, the surface tensions of propionic acid solutions in water are... 

The increase in retention at a given concentration depends on both the anion and the cation of the salt. Speciflcally, the retention increment depends on the molal surface tension increment of the salt. Table 13.1 contains this value for various salts. The higher the value, the greater is the retention at a pven concentration. It should be noted that the order in the table parallels the Hofmeister salting-out series (12). 

Theoretical discussions of the surface tension increments try to explain the trends noted for the various ions. Aveyard and Saleem (1976) related the 577 of an electrolyte solution to the product of its molality and its osmotic coefficient (p ... 

PHYSICAL-CHEMICAL PROPERTIES OF FUSED ORGANIC SALTS. II. CONDUCTANCE, MOLAL VOLUME, AND SURFACE TENSION OF FUSED ALKYLAMMONIUM CHLORIDES. 

---