Osmotic pressure of solutions

The osmotic pressure of solutions of polystyrene in cyclohexane was measuredf at several different temperatures, and the following results were obtained ... 

Numerous measurements of the conductivity of aqueous solutions performed by the school of Friedrich Kohhansch (1840-1910) and the investigations of Jacobns van t Hoff (1852-1911 Nobel prize, 1901) on the osmotic pressure of solutions led the young Swedish physicist Svante August Arrhenius (1859-1927 Nobel prize, 1903) to establish in 1884 in his thesis the main ideas of his famous theory of electrolytic dissociation of acids, alkalis, and salts in solutions. Despite the sceptitism of some chemists, this theory was generally accepted toward the end of the centnry. 

Understand the clinical significance of the osmotic pressures of solutions... 

In case of solutions of high Molecular weight compounds, the selection of semi-permeable membrane is easier, because the solvent and the solute molecules are quite different in their size. The relationship between the Osmotic pressure of solution of a macromolecular compound and the Molecular weight is widely used for determination of Molecular weights and in the study of the interaction between the solvent and the solute molecules in the solution. 

The osmotic pressure of solutions of a fractionated, atactic poly(isopropylacrylate) solution was measured at 25°C with the following results ... 

When the feed concentration is as small as those considered in this study, the osmotic pressure of solutions is negligible. Therefore, PR/PWP may be expected to be nearly equal to unity. However, for cases V and VI, in which strong attractive forces work between membrane and solute, PR/PWP... 

Data collected with membranes of this type played an important part in the formulation of present-day solution theory—so much so that the authors have used this theory without hesitation to compute osmotic pressures of solutions whose osmotic pressures have never been precisely measured. Such a solution is sea water. The copper ferrocyanide membrane is leaky to solutions of strong electrolytes. Some data have been obtained on weak solutions of strong electrolytes by the Townend method (16), but no one has made precise measurements on the osmotic pressure of sea water. 

Example The following data were obtained on the osmotic pressure of solutions of y-globulin in 0.15 M NaCl at 37 C ... 

The osmotic pressures of solutions of calcium ferrocyanide in water have been determined for various concentrations,5 and the results indicate that the negative radicles are associated, yielding the double ion [Fe(CN)6]2"""". 

The osmotic pressure of solutions are discussed here as an introduction to the concept of osmotic pressme in suspension [21]. The phenomena of osmotic pressure is illustrated by a semipermeable membrane filled with a sugar solution immersed in water. The pressure inside the membrane, p + it, is large than that in the water, p, according to the formula... 

Determination of the osmotic pressure of solutions in the presence of other solutes and biologic-binding processes can indicate clearly changes in the amount of water bound or, more exactly, the amount of water that can no longer interact freely with the solutes. Such methods have been useful particularly to determine the DNA-protein interactions (29). 

By definition, UF membranes are freely permeable to inorganic salts and other molecules with MW less than about 1000. Because it is these species that generally create most of the osmotic pressure of solutions, the net osmotic pressure difference across UF membranes is generally quite small and therefore small applied pressures can be used. Because these membranes are more open than RO membranes, there is less necessity to produce very thin membranes in order to achieve high water fluxes. 

Vapour Pressure and Osmotic Pressure of Solutions of Calcium Ferbocyanide at 0°C. 

This simple law was first deduced in 1886 by van t Hoff from the analogy between the dissolved and the gaseous states, and was confirmed by the experiments of Pfeffer on the osmotic pressures of solutions of cane sugar, and of de Vries on the plas-molysis of plant cells in various solutions. Subsequent experiments, based for the most part on van t Hoff s thermodynamical deductions, have completely established this simple theory (for dilute solutions at least). 

The thermoelectrical behaviour of many alloys is typical. Their thermoelectric potential is often much higher than that of the pure metals of which they are composed. These facts cannot be deduced from thermodynamics, which in general can tell us nothing new about constants which are characteristic of the chemical nature of substances. We must have recourse here to special theories, just as in the calculation of the osmotic pressure of solutions. We may mention that the electronic and molecular theories of R. Schenck I and A. Bernoulli J have done valuable service in this direction. 

Staudinger and Husemann determined the osmotic pressure of solutions of a potato starch acetate which had been fractionated into four parts by precipitation of its chloroform solution with ether. The molecular weights of the fractions ranged from 45,000 to 275,000. All of the fractions were soluble in chloroform, but fractions of low molecular weight were also soluble in acetone. For various concentrations of solute in either chloroform or acetone, the osmotic pressure did not increase in direct proportion to the solute concentration, but the deviation from van t Hoff s law was the smallest in the case of the acetone solutions. Osmotic pressure measurements on amylose and amylopectin tri-acetates dissolved in tetrachloroethane have been made by Meyer and co-workers, who have deduced molecular weights for these substances of approximately 78,000 and 300,000, respectively (see above discussion of the purity of these fractions). 

The osmotic pressure of solutions is of particular importance with parenteral administration. (In the case of the human blood serum it is about 7.5 bar at 37 °C.) It is not very affected by the molecular weight and the concentration of povidone. The simplest method for determining the osmotic pressure uses the Van t Hoff equation. 

Many molecular parameters, such as ionization, molecular and electronic structure, size, and stereochemistry, will influence the basic interaction between a solute and a solvent. The addition of any substance to water results in altered properties for this substance and for water itself. Solutes cause a change in water properties because the hydrate envelopes that are formed around dissolved molecules are more organized and therefore more stable than the flickering clusters of free water. The properties of solutions that depend on solute and its concentration are different from those of pure water. The differences can be seen in such phenomena as the freezing point depression, boiling point elevation, and increased osmotic pressure of solutions. 

Comparison of Osmotic Pressures of Solutions of different Substances in the same Solvent... 

The second virial coefficient can be obtained from the slope of the straight line portion of the (II/c) versus c plot by removing the terms in Eqs. (4.41)-(4.43). When plotted according to Eq. (4.41), the osmotic pressures of solutions of the same polymer in different solvents should yield plots with the same intercept (at c = 0) but with different slopes (see Fig. 4.5), since the second virial coefficient,... 

The solution to the problem was discovered in 1874 by Jacobus Henricus van t Hoff, 22 years old, and Joseph Achille Le Bel, age 27. Although they both worked in the laboratory of Adolph Wurtz in Paris in 1874, their discoveries were completely independent. Van t Hoff would continue to make major contributions to physical chemistry and won its first Nobel Prize (1901) for his discovery of laws of osmotic pressure of solutions. 

FIGURE 300. Figures from the first English edition of J.H. van t Hoff s Chemistry in Space (Oxford, 1891). His discovery simultaneously with (independently of) LeBel may have played some role in his receipt of the first Nohel Prize in Chemistry (1901). However, the prize was awarded specifically for his discovery of laws of osmotic pressure of solutions. 

Pfeffer s research had been on osmotic pressure. It had been well established from early in the eighteenth century that when a solution is separated from pure water by a semipermeable membrane such as a bladder, the water permeates the membrane and dilutes the solution, setting up a pressure if the volume of the latter is prevented from increasing. This pressure was termed osmotic pressure. Pfeffer in 1877 was able, by depositing copper ferrocyanide on the walls of a porous pot, to prepare semipermeable membranes that were permeable to water, but were not permeable to dissolved sugar. Using these semipermeable membranes, he was able to measure the osmotic pressures of solutions. ... 

To estimate molecular weights of several samples of poljretjrene from measurements of osmotic pressure of solutions in toluene. 

The osmotic pressure of solutions and especially the osmotic pressure in the boundary layer reduces the effective transmembrane pressure. To estimate the possible effect, ionic strength and osmotic pressure values for various salt solution compositions are summarised in Table 7.22. 

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