Osmotic value calculation

Validation of the Osmotic Coefficient Calculation. The results for the osmotic coefficients calculated for a series of brines representing an evaporative concentration sequence of sea water brines are given in Figure 1 and Table I. In Figure 1, the agreement between the measured (10) and calculated osmotic coefficients are compared. Table I also includes the coefficient of variation between the calculated and measured values. The maximum coefficient of variation encountered was 0.90 percent and... 

Calculate the osmotic pressure at 25°C of a 0.50 M solution of Ca(N03)2 in water. (Assume that i = 3.0.) Would you expect the measured osmotic pressure of 0.50 M Ca(N03)2 to be higher or lower than the value calculated Explain. 

The osmotic pressure values given in Table 23 were obtained for 10% solutions of low-molecular povidones in water, using the equation given in Table 22. These values apply to pure povidone. As povidone contains only traces of impurities, e.g. 1 ppm vinylpyrrolidone, the osmotic pressure is hardly affected. This is confirmed by comparing the values measured for povidone K 17 with those calculated, in Table 23. The osmotic pressure calculated for a solution containing 1 ppm vinylpyrrolidone is given for reference. 

Fig. 8.4. Osmotic pressure in the semi-dilute regime a comparison between the values calculated by Flory and Huggins...

A U. luO-L solution is made by dissolving u.44i gof CaCl2(s) in water, (a) Calculate the osmotic pressure of this solution at 27 "C, assuming that it is completely dissociated into its component ions, (b) The measured osmotic pressure of this solution is 2.56 atm at 27 C. Explain why it is less than the value calculated in (a), and calculate the van t Hoff factor, i, for the solute in this solution. (See the A Closer Look box on Colligative Properties of Electrolyte Solutions in Section 13.5.) (c) The enthalpy of solution for CaCl2 is AH = —81.3 kj/mol. If the final temperature of the solution is 27 °C, what was its initial temperature (Assume that the density of the solution is 1.00 g/mL, that its specific heat is 4.18 J/g-K, and that the solution loses no heat to its surroundings.)... 

As a measure of the tonicity of blood one can calculate with the osmotic value because active substances and additives cannot pass the membrane of the erythrocyte (see Sect. 18.5.2). The osmotic value of blood is around 290 mOsm/kg. Some parenteral fluids however contain substances that can pass the membrane fast ethanol, glycerol, urea. Hyperosmotic solutions of these substances may cause haemolysis so they are hypotonic. The iso-osmotic concentration of ethanol is for example 1.39 % m/m. Ethanol 5 % v/v infusion fluid is therefore hyperosmotic but appears to be practically isotonic. 

If an active substance or excipient substantially contributes to the osmotic value, it may be necessary to calculate this contribution. This can be done in practice by three different calculation methods. The choice of the method depends on which physical characteristics of the substances are available. 

Method 1 If the molecular weight and the dissociation type (f-value. Table 18.21) are known, the osmotic value can be calculated using apart of equation 18.16, namely ... 

Method 1 is exemplified by the calculation of the osmotic value of betaxolol 1 % eye drops ... 

Method 2 If the iso-osmotic concentration of a substance is known, the osmotic value can be easily calculated. In Martindale, these values are often specified in the description of substances [11]. In the Merck Index and in the Handbook of injectable drugs, the iso-osmotic concentrations for a large number of substances are listed in a table [6, 37]. 

A 4.1 % w/v solution of pilocarpine hydrochloride is iso-osmotic (293 mosmol as determined by measuring its freezing point depression). A 2 % wA pilocarpine hydrochloride thus contributes to about 50 % of the iso-osmotic value (the osmolarity as determined at pH 6 is 147 mosmol). The other 50 % should be provided by the excipients. Iso-osmotic stock solutions (see also Sect. 10.7.1) for the preparation of eye drops could be very useful for the purpose of easy calculation. The stock solution Boric acid-benzalkonium solution FNA (see Table 10.10) is nearly iso-osmotic (boric acid is iso-osmotic at a concentration of 19 mg/mL). The contribution to the osmotic value of the benzalkonium chloride 100 mg/L is too small and can be neglected in the calculations. Without adjusting the pH, 50 % v/v of Boric acid-benzaUconium solution would be needed. But because the stability of pilocarpine is optimal at pH 6.5, the pH is adjusted with 3.75 mg/mL borax to 6.5. As 3.75 mg/mL borax contributes 15 % to the osmotic value, 35 % is left for the Boric acid-benzalkonium solution. 

A polyisobutylene sample has M = 400,000. The second virial coef cient of the polymer in chlorobenzene solution at 25°C is F2 = 94.5 cm /g. Calculate the osmotic pressure in g/cm of 0.30 g/dL solution of this polymer in chlorobenzene at 25°C. Compare this with the value calculated for an ideal solution. [Chlorobenzene density at25°C is 1.11 g/cm. ]... 

Stability of W/OAV multiple emulsion containing Span 80 and Tween 80 was evaluated with respect to sodium chloride and sodium salicylate concentrations in the inner water phase (Jiao and Burgess, 2002). In this study we observed that the multiple emulsion droplets deformed and there was coalescence of the inner aqueous droplets as we applied an external force (i.e., a microscopic covershp) to multiple emulsion samples on a microscope slide. Under certain conditions (e.g., lipophihc surfactant concentration and internal phase osmotic pressure) the destabilized multiple emulsions formed unique metastable structures that had a dimpled appearance. The formation of these metastable structures correlated with the real time instability of the W/O/W multiple emulsions investigated. Our study revealed that emulsions with a salt concentrations closer to the optimal value calculated by using (1.7) had maximum stability. 

Fig. 4. Osmotic coefficient calculated for the following values of the parameter A (1) 2.76, (2) 3.40, (3) 3.80, (4) 4.00. The circles represent the experimental values for solutions of HPSS. (Reference [15], Figure 2.)...

For the chain (homogenous) consisting of one con-former, osmotic forces are similar to the ones stretching the molecule by the ends. Then, labor of the distance being estimated at constant temperature T , one can estimate 5ch value from the condition = F AR = T ASch)- If a more accurate estimation of the distance change valRe between the ends is required, one may calculate the R value, taking into account the distribution function of the distances between the ends R. The value of the mean-square distances between the ends of the chain, being stretched by forces, applied to the ends equals [14] ... 

This is a large value for a molar mass, but it is reasonable because biological molecules often are quite large. As in any calculation, be careful to express all data in appropriate units. The osmotic pressure was measured to two significant figures, so the result has two significant figures. 

Figure 15.1 Calculated and experimental osmotic coefficients for Na SiO The line represents the calculated values.

Osmolality is a measure of the number of osmotically active particles per unit of solution, independent of the weight or nature of the particle. Equimolar concentrations of all substances in the undissociated state exert the same osmotic pressure. Although the normal serum osmolality is 280 to 300 mOsm/kg (280 to 300 mmol/kg), multiple scenarios exist where this value becomes markedly abnormal. The calculated serum osmolality helps determine deviations in TBW content. As such, it is often useful to calculate the serum osmolality as follows ... 

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