Isotonic coefficient

A theory close to modem concepts was developed by a Swede, Svante Arrhenins. The hrst version of the theory was outlined in his doctoral dissertation of 1883, the hnal version in a classical paper published at the end of 1887. This theory took up van t Hoff s suggeshons, published some years earlier, that ideal gas laws could be used for the osmotic pressure in soluhons. It had been fonnd that anomalously high values of osmotic pressure which cannot be ascribed to nonideality sometimes occur even in highly dilute solutions. To explain the anomaly, van t Hoff had introduced an empirical correchon factor i larger than nnity, called the isotonic coefficient or van t Hoff factor,... 

Because of dissociation and the resulting increase in the total number of particles in solution, the parameters of the colUgative properties assume higher values. These values are proportional to the total concentration, c, of particles (ions and undissociated molecules) in the solution, which for a binary electrolyte is given by [1 + a(X(, - l)]q. The isotonic coefficient i is the ratio of and the concentration c, that would be observed in the absence of dissociation ... 

ISOTONIC BUFFERS OSTWALD RIPENING OSTWALD SOLUBILITY COEFFICIENT... 

The coefficient of hydraulic permeability (Lp) of ozone-treated bean leaf tissue tends to decrease when measured by water loss or uptake (Fig. 6). Here, ozone-treated tissue was equilibrated with 0.2 M mannitol (approximately isotonic) immediately after exposure. The tissue was then either allowed to take up tritiated water or, after a period of tritiated water uptake, allowed to lose tritiated water into a mannitol solution. In both the influx and efflux experiments, ozone-treated tissue transported tritiated water at a lower rate than control tissue. 

Fig. 1 Those parts of the level schemes of the Y isotones at N 60, which are observed in the decay of isomers (the hatched levels in are populated in the B decay). The theoretical conversion coefficients are taken from [R0E78]. h = log(H)/n, where H is the hindrance of the transitions and n = K-j - Kf - A the degree of K forbiddenness [MEY85].

Standard curve A series of dilutions of bovine serum albumin in isotonic 5 mM phosphate buffer, pH 7.4, are prepared containing between 0 and 100 pg protein in 0.1 ml volume and the assay is performed as described above on each dilution. The exact concentration of the bovine serum albumin stock solution is determined using the molar absorption coefficient of 45000 for bovine serum albumin at 279 nm after diluting to approximately 0.2 g/1. 

In the foregoing method the mean ionic activity coefficient of the solute has been calculated from actual vapor pressure data. If the osmotic coefficients for a reference substance are known over a range of concentrations, the activity coefficients of another electrolyte can be derived from isopiestic measurements, without actually determining the vapor pressures. If w, and p refer to an experimental electrolyte and wr, 0r and vr apply to a reference electrolyte which is isopiestic (isotonic) with the former, then by equation (39.46)... 

In red cells, this coefficient is usually measured by the zero time method [18] in which a suspension of cells in isotonic buffer is mixed rapidly with various test solutions of the probing molecule under study. The initial cell volume change (limdK/dr) is plotted against the various concentrations of the probing molecule. 

It is worth emphasis that the verification of isotonic transport for a particular model necessitates the solution of Eqns. 5 and 6. In general, the simple calculation of (Cr)o, the reabsorbate concentration with exactly equal bathing media, is not sufficient. Nevertheless, (Cr)q is an important theoretical aspect of a model and has been used to define the coupling coefficient of osmotic transport [ 15] by... 

Thus, the osmotic coupling coefficient is the ratio of the actual volume flow observed with equal bathing media relative to the virtual volume flow that would be necessary for reabsorption to be isotonic. In the models we shall consider, 0 < y < 1. For tight couphng, Y 1 in an uncoupled system y = 0. y has also been termed the efficiency of osmotic transport [16]. 

In his early analysis of isotonic transport. Diamond [13] tried to use measured values of the whole epithelial water permeability, Lp, in place of the quantity Llb-The unacceptably large osmotic deviations from isotonicity that he computed caused him to reject the elementary compartment model of the lateral intercellular space. We should reconsider, therefore, the requirements imposed upon the elementary compartment model by the experimental data on rabbit gallbladder (Table 1). For N/Cq = 1.47-10 cm/s and C/Q = 0.27, Eqn. 84 requires = 5.5-10 cm/s. Eqn. 86 may be used to give a lower bound on the coupling coefficient. If mucosal equilibrium is within 2% of exact isotonicity then — C /Cq = 0.02 so that y = 0.95. Thus, if Lp = 1.7- lO"" cm/s.osm, Eqn. 85 implies L b is at least 34-10" cm/s.osm. It remains to consider these model predictions for and Llb i relation to the pertinent experimental data. 

On the other hand, the coefficient was estimated from the isotonic method... 

Table 3.5 Rate constants (s ) and tunneling coefficients for CIONO2 + rrn j-rToD with isotonic snhstitiition."...

Cuprophan membranes made from regenerated cellulose are frequently used in hemodialysis. Model this membrane as one consisting of cylindrical capillaries of radius 18 A. Determine the separation factors of the dialysis membrane for two solutes, urea and vitamin B12. The characteristic radii of urea and vitamin B12 are 2.8 A and 8.5 A, respectively. The diffusion coefficients of urea and vitamin B12 at infinite dilution in isotonic saline at 37 °C are 1.81 x 10 and 0.38 x 10" cm /s, respectively. Compare the result for the given pore size estimate with that obtained from the data of Colton et al (1971), namely 16 (based on effective diffusion coefficients without any consideration of equilibrium partition coefficients in their Figure 6). (Ans. 23.5.)... 

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