Ethyl osmotic pressure

The osmotic pressure of polystyrene fractions in toluene and methyl ethyl ketone was measuredt at 25°C and the following results were obtained ... 

An HFRO module with a membrane area of 300 m is used to teraove methyl ethyl ketone (MEK) from wastewater. The feed to the module has a flowrate of 9 x 10 m /s, an MEK composition of 9500 ppm, and an osmotic pressure of 5.2 atm. The average pressure difference across the membrane is 50 atm. The permeate is collected at atmos eric pressure. The water recovery for the module is 86%, and the solute rejection is 98%. Evaluate the transport parameters Ay and (p ujKS). 

TABLE 15.1. Osmotic Pressure Data for Polyvinyl Acetate in Methyl Ethyl Ketone at 10°C... 

Table 15.1 contains osmotic pressure data calculated from the work of Browning and Ferry [3] for solutions of polyvinyl acetate in methyl ethyl ketone at 10°C. Plot H/vv against w, fit the data to a quadratic polynomial, and calculate the number-average molar mass from the intercept with the n/w axis. 

The results obtained for the osmotic pressures and electric conductivities of aqueous solutions of calcium and strontium ferroeyanides (see pp. 208 and 220) indicate that these molecules possess the double formula, M4[Fe(CN)6]2. On the other hand, tetra-ethyl ferrocyanide is known to have the single formula, (C2H5)4Fe(CN)6.s... 

Suppose 0.125 g of a protein is dissolved in 10.0 cm of ethyl alcohol (C2H5OH), whose density at 20°C is 0.789 g cm . The solution rises to a height of 26.3 cm in an osmometer (an apparatus for measuring osmotic pressure). What is the approximate molar mass of the protein ... 

Estimate the osmotic pressure associated with 24.5 g of an enzyme of molecular weight 4.21 X 10 dissolved in 1740. mL of ethyl acetate solution at 38.0°C. 

As discussed in Chapter 2 of this Handbook, the osmotic pressure can provide one of the most direct methods of determination of interaction parameter. The estimation of these interaction parameters is applied to PS/PVME blends in toluene and ethyl benzene respectively [Shiomi et al., 1985]. It is observed that in toluene varied with composition from -0.044 to h-0.0093, while in ethyl benzene it increased with PVME content from -0.06 to 0.027. 

Table 16.5). In this instance, however, the particles were dispersed in cyclohexane rather than ethyl benzene. Moreover, the dispersions were said to undergo phase separation rather than particle flocculation. The data reported by de Hek and Vrij for two particle sizes suggest that V2 is inversely related to the particle radius, rather than the square root of the particle radius. The radius dependence observed for this system is that which would be predicted if the ideal van t Hoff term was predominantly responsible for the osmotic pressure of the polymer solution, since AG would then be proportional to V2 a, i.e. V2 oc 1/a. This result is scarcely surprising since cyclohexane is a poor solvent for polystyrene (0=34°C). In those circumstances, only the ideal contribution to the osmotic pressure need be considered. The different radius dependences observed in such experiments is accordingly explained.

Example 12.3 The data on the osmotic pressure of a sample of poly(vinyl acetate) in methyl ethyl ketone at 25°C are shown below ... 

Sheetz [10c] developed a model which tried to rationalize the observation that most latex dispersions diy from the peripheiy inward. He construded experiments using dispersion-saturated blotting paper whidi avoided die problem. In this system, he noted that latex dispersions containing vinylidene chloride as a comonomer dried more slowly, at later stages, than poly[(ethyl aciylate)-co-(methyl methacrlyate) (P(EA-co-MMA)) latex dispersions, and noted that the latter formed films more permeable to water vapour. He therefore proposed that protrusion of the meniscus below the tops of the latex at close packing was accompanied by skin formation that closed the pores to further evaporation of water. Water vapour then had to diffuse through the continuous polymer film, and the resulting (osmotic) pressure led to particle deformation and film densification. 

Fig. 7. Influence of solvents of different polarity on the osmotic pressure of ethyl cellulose.

FIG. 16 Alcohol and ethyl esters content before (BF) and after (AF) freezing of melon spheres cv. Rony not pretreated (RAW) or air dried at 80 °C up to 50% weight reduction without (AD) or following 60-min osmotic dehydration (OAD) in 60% (w/w) sucrose solution at 25 °C at atmospheric pressure (Lo Scalzo et al., 2001). 

The pressure required to drive water out of mixtures of various concentrations of ethyl alcohol against pure water at 30°C is calculated from the osmotic equation... 

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