Osmotic-pressure sentence examples

osmotic-pressure
  • Van Hoff pointed out that measurements of osmotic pressure confirmed this value in the case of dilute solutions of cane sugar.

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  • Thermodynamic theory also indicates a connexion between the osmotic pressure of a solution and the depression of its freezing point and its vapour pressure compared with those of the pure solvent.

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  • It' would be possible for a body in solution to be dissociated into non-electrical parts, which would give osmotic pressure effects twice or three times the normal value, but, being uncharged, would not act as ions and impart electrical conductivity to the solution.

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  • The dissociation theory was originally suggested by the osmotic pressure relations.

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  • The result of the investigation shows that the electrical work Ee is given by the_equation Ee =1 where v is the volume of the solution used and p its osmotic pressure.

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  • When the dissolved molecules are uniformly distributed, the osmotic pressure will be the same everywhere throughout the solution, but, if the concentration vary from point to point, the pressure will vary also.

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  • There must, then, be a relation between the rate of change of the concentration and the osmotic pressure gradient, and thus we may consider the osmotic pressure gradient as a force driving the solute through a viscous medium.

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  • On the analogy between this case and that of the interface between two solutions, Nernst has arrived at similar logarithmic expressions for the difference of potential, which becomes proportional to log (P 1 /P 2) where P2 is taken to mean the osmotic pressure of the cations in the solution, and P i the osmotic pressure of the cations in the substance of the metal itself.

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  • Much more important is the effect of the alteration in the amount of crystalloids in the tissues and blood and therefore of the alteration in the osmotic pressure between these.

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  • Thus differences in osmotic pressure may be much more powerful in producing oedema than mere differences in blood pressure.

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  • Now differences in the amount of crystalloids cause alteration in osmotic pressure while the proteid content affects it but little; and of the crystalloids the chlorides appear to be those most liable to variation.

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  • Some other observers, however, have not got such good results with a chloride-free diet, and Marishler, Scheel, Limbecx, Dreser and others, dispute Widal's hypothesis of a retention of chlorides as being the cause of oedema, in the case of renal dropsy at all events; they assert that the chlorides are held back in order to keep the osmotic pressure of the fluid, which they assume to have been effused, equal to that of the blood and tissues.

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  • Thus, while increased pressure in the blood or lymph vessels may be one factor, and increased permeability of the capillary endothelium another, increased osmotic pressure in the tissues and lymph is probably the most important in the production of dropsy.

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  • According to the investigations of Svante Arrhenius the osmotic pressure in atmospheres may be obtained by simply multiplying the temp rature of freezing (r) by the factor -12.08, and it varies with temperature (t) according to the law which holds good for gaseous pressure.

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  • Pt = Po(' +0 00367t) and can thus be reduced to its value at o° C. Sigurd Stenius has calculated tables of osmotic pressure for sea-water of different degrees of concentration.

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  • The relation of the elevation of the boiling-point (t°) to the osmotic pressure (P) is very simply derived from the formula t=o 02407P 0, while the reduction of vapour pressure proportional to the concentration can be very easily obtained from the elevation of the boiling-point, or it may be obtained directly from tables of vapour tension.

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  • The importance of the osmotic pressure of sea-water in biology will be easily understood from the fact that a frog placed in sea-water loses water by exosmosis and soon becomes 20% lighter than its original weight, while a true salt-water fish suddenly transferred to fresh water gains water by endosmosis, swells up and quickly succumbs.

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  • Pfeffer, made known the phenomena of the osmotic pressure which is set up by the passage of solvent through a membrane impermeable to the dissolved substance or solute.

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  • van't Hoff in 1885, who showed that Pfeffer's results indicated that osmotic pressure of a dilute solution conformed to the well-known laws of gas pressure, and had the same absolute value as the same number of molecules would exert as a gas filling a space equal to the value of the solvent.

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  • But such a pressure represents the equilibrium osmotic pressure discussed above.

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  • Therefore the equilibrium osmotic pressure of a solution is connected with the vapour pressure, arid, in a very dilute solution, is expressed by the simple relation just given.

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  • In any solution, then, the osmotic pressure represents the excess of hydrostatic pressure which it is necessary to apply to the solution in order to increase its vapour pressure to an equality with that of the solvent in the given conditions.

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  • By imagining that a dilute solution is put through a thermodynamic cycle we may deduce directly relations between its osmotic pressure and its freezing point.

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  • Now the work done by allowing a small quantity of solvent to enter reversibly into an osmotic cylinder is measured by the product of the osmotic pressure into the change in volume.

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  • Hence the osmotic pressure is measured by the work done per unit change of volume of the solution.

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  • The result of our consideration, therefore, is that the osmotic pressure of a dilute solution of a volatile solute must have the same value as the gaseous pressure the same number of solute particles would exert if they occupied as gas a volume equal to that of the solution.

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  • The reasoning given above is independent of the temperature, so that the variation with temperature of the osmotic pressure of a dilute solution must be the same as that of a gas, while Boyle's law must equally apply to both systems. Experimental evidence confirms these results, and extends them to the cases of non-volatile solutes - as is, indeed, to be expected, since volatility is merely a matter of degree.

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  • In the limit then, when the concentration of the solution becomes vanishingly small, theory shows that the osmotic pressure is equal to the pressure of a gas filling the same space.

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  • A quantity of gas measured by its molecular weight in grammes when confined in a volume of one litre exerts a pressure of 22.2 atmospheres, and thus the osmotic pressure of a dilute solution divided by its concentration in gramme-molecules per litre has a corresponding value.

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  • Putting the absolute temperature of the freezing point of water as 273°, the osmotic pressure P as 22.2 atmospheres or 22.4X106, C.G.S.

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  • Since, in dilute solutions, the osmotic pressure has the gas value, we may apply the gas equation PV=nRT =npvi to osmotic relations.

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  • The experiments of Raoult on solutions of organic bodies in water and on solutions of many substances in some dozen organic solvents have confirmed this result, and therefore the theoretical value of the osmotic pressure from which it was deduced.

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  • They merely show that, in the conditions of the particular experiments, the thermodynamic equilibrium value of the osmotic pressure cannot be reached - the thermodynamic or theoretical osmotic pressure (which must be independent of the nature of the membrane provided it is truly semi-permeable) is a different thing from the equilibrium pressure actually reached in a given experiment, which measures the balance of ingress and egress of solvent through an imperfect semi-permeable membrane.

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  • 13 required for osmotic equilibrium through a semi-permeable wall below is now very great, since the osmotic pressure of strong solutions may reach many hundred atmospheres.

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  • The osmotic pressure (defined as the difference in the hydrostatic pressures of the solution and solvent when their vapour pressures are equal and they are consequently in equilibrium through a perfect semi-permeable membrane) may also depend on the absolute values of the hydrostatic pressures, as may the vapour pressure of the liquids.

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  • To investigate the osmotic pressure of a' strong solution we may consider the hydrostatic pressure required to increase its vapour pressure to an equality with that of the solvent.

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  • The osmotic pressure Po is the difference of the hydrostatic pressures P' and P of the solution and the solvent when their vapour pressures are equal.

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  • If V =V' there is no change in osmotic pressure with hydrostatic pressure, and osmotic pressure depends on concentration and temperature only.

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  • If we measure the osmotic pressure Po when the solvent is under its own vapour pressure only, that is, when P = p = Po, the term involving V vanishes, and the limit of integration P' becomes Pod-p. If we assume that V', the volume change on dilution, varies regularly or not appreciably with pressure, we may write the first integral as V' (P o -{- p - p') where V' now denotes its mean value between the limits.

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  • From this equation the osmotic pressure Po required to keep a solution in equilibrium as regards its vapour and through a semi-permeable membrane with its solvent, when that solvent is under its own vapour pressure, may be calculated from the results of observations on vapour pressure of solvent and solution at ordinary low hydrostatic pressures.

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  • Approximately one degree lowering of freezing point corresponds with a change of 12 atmospheres in the osmotic pressure.

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  • Putting in these values and integrating we have, neglecting terms involving 0', P=12.06 0-0.021 O s where P is the osmotic pressure in atmospheres.

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  • Frazer, who have made direct measurements of osmotic pressure of solution of cane-sugar, have also measured the freezing points of corresponding solutions.

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  • Thus the theory of the connexion of osmotic pressure with freezing point (like that with vapour pressure) seems to give results which accord with experiments.

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  • At the limit of dilution, when the concentration of a solution approaches zero, we have seen that thermodynamical theory, verified by experiment, shows that the osmotic pressure has the same value as the gas pressure of the same number of molecules in the same space.

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  • The conceptions of osmotic pressure and ideal semi-permeable membranes enable us to deduce other thermodynamic relations between the different properties of solutions.

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  • If it be filled with a solution and the bottom immersed in the pure solvent, pressure equal to the osmotic pressure must be exerted on the piston to maintain equilibrium.

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  • the osmotic pressure is proportional to the absolute temperature.

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  • This result must hold good for any solution, but if the solution be dilute when saturated, that is, if the solubility be small, the equation shows that if there be no heat effect when solid dissolves to form a saturated solution, the solubility is independent of temperature, for, in accordance with the gas laws, the osmotic pressure of a dilute solution of constant concentration is proportional to the absolute temperature.

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  • os The result is to change the relation between temperature and the osmotic pressure of a solution of constant concentration, a relation which, in very dilute solutions, is a direct proportionality.

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  • Whether osmotic pressure be due to physical impact or to chemical affinity it must necessarily have the gas value in a dilute solution, and be related to vapour pressure and freezing point in the way we have traced.

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  • Boltzmann offered a demonstration of the law of osmotic pressure in dilute solutions, based on the idea that the mean energy of translation of a molecule should be the same in the liquid as in the gaseous state.

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  • The osmotic pressure of a solution depends on the concentration, and, if we regard the difference in that pressure as the effective force driving the dissolved substance through the solution, we are able to obtain the equation of diffusion in another form.

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  • When the solution is dilute enough for the osmotic pressure to possess.

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  • Since some ions are more mobile than others, a separation will ensue when water is placed in contact with a solution, the faster moving ion penetrating quicker into the water under the driving force of the osmotic pressure gradient.

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  • The osmotic pressure of an electrolyte consisting of two ions is double that of a non-electrolyte.

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  • This removal of graphite doubtless further stimulates the formation of graphite, by relieving the mechanical and perhaps the osmotic pressure.

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  • Vapour-Pressure and Osmotic Pressure.

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  • His observations showed that the osmotic pressure was nearly proportional to the concentration and to the absolute temperature over a limited range.

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  • Van't Hoff showed that the osmotic pressure P due to a number of dissolved molecules n in a volume V was the same as would be exerted by the same number of gas-molecules at the same temperature in the same volume, or that PV = ROn.

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  • Arrhenius, by reasoning similar to that of section 5, applied to an osmotic cell supporting a column of solution by osmotic pressure, deduced the relation between the osmotic pressure P at the bottom of the column and the vapour-pressure p" of the solution at the top, viz.

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  • 1896, 42, p. 298) has accordingly defined the osmotic pressure of a solution as being the hydrostatic pressure required to make its vapourpressure equal to that of the pure solvent at the same temperature, and has shown that this definition agrees approximately with Raoult's law and van't Hoff's gas-pressure theory.

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  • It is probable that osmotic pressure is not really of the same nature as gas-pressure, but depends on equilibrium of vapour-pressure.

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  • colloid osmotic pressure of the plasma.

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  • This increases osmotic pressure in astrocytes, resulting in cerebral edema.

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  • Nerve impulses from the hypothalamus stimulate the posterior pituitary to produce ADH when the osmotic pressure of the blood rises.

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  • K +) created local osmotic pressure gradients which could only be abolished by conversion of LDW to high density water (HDW ).

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  • All dissolved substances will contribute to the osmotic pressure of a fluid.

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  • Marchal points out the analogy of this phenomenon to the artificial polyembryony that has been induced in Echinoderm and other eggs by separating the blastomeres, and suggests that the abundant food-supply afforded by the host-larva is favourable for this multiplication of embryos, which may be, in the first instance, incited by the abnormal osmotic pressure on the egg.

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  • The evidence which led Arrhenius to this conclusion was based on van 't Hoff's work on the osmotic pressure of solutions (see Solution).

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  • This equilibrium pressure is called the osmotic pressure of the solution, and thermodynamic theory shows that, in an ideal case of perfect separation between solvent and solute, it should have the same value as the pressure which a number of molecules equal to the number of solute molecules in the solution would exert if they could exist as a gas in a space equal to the volume of the solution, provided that the space was large enough (i.e.

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  • This increased osmotic pressure is again due to accumulation of crystalloids in the tissues, either products of metabolism due to deficient oxidation from alteration in the blood or other cause, or, it may be, as in some cases of nephritis, owing to a.

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  • Pt = Po(' +0 00367t) and can thus be reduced to its value at o° C. Sigurd Stenius has calculated tables of osmotic pressure for sea-water of different degrees of concentration.

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  • The relation of the elevation of the boiling-point (t°) to the osmotic pressure (P) is very simply derived from the formula t=o 02407P 0, while the reduction of vapour pressure proportional to the concentration can be very easily obtained from the elevation of the boiling-point, or it may be obtained directly from tables of vapour tension.

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  • Another application of the theory of energy enables us to coordinate the osmotic pressure of a dilute solution with the pressure of a gas occupying the same space.

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  • Putting the absolute temperature of the freezing point of water as 273°, the osmotic pressure P as 22.2 atmospheres or 22.4X106, C.G.S.

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