Silver ionic strength dependence

If, instead of thallium chloride, some other salt that does not have a common ion with AgCl (for example. NaNOs) had been introduced into the aqueous solution, the solubility of silver chloride would have increased because of the ionic-strength dependence of the ionic activity coefficient. Thus, if NaNOs were present in the same concentration as, but instead of, thallium chloride, we would have... 

Fig. 3.70 depicts the /i(pH) dependence of lyso PC films at po = 42 Pa, t = 30°C and constant ionic strength. In the pH range from 4.2. to 5.8, equilibrium silver-coloured films with mean h values of about 50 - 70 nm were formed. In some experiments, NBF of 7.6 nm thickness were formed, thus marking a fluctuation zone where both silver-coloured and NBF could be observed. Below pH = 4.1 only NBF formed. 

To establish a good in vitro/in vivo correlation, the composition and ionic strength of the receptor solution must be adjusted. For fentanyl, the best correlation was obtained with a receptor solution comprised of a 10-fold dilution of modified Dulbecco phosphate-buffered saline (without calcium or magnesium) at pH 7.4. The currents tested in vitro ranged from 0 to 400 pA and were applied to a silver anode and a silver chloride cathode using a constant current power supply. The in vitro data presented in Fig. 5 clearly demonstrate the expected linear dependence of fentanyl delivery on current and the excellent correlation to the in vivo data. 

Figure 10-7. The pH dependence of the solubility of silver acetate at 25° and 0.1 M ionic strength.

Since the electromotive force of a cell depends on the activity of the ions of the electrolyte it is possible to determine activities potentiometrically, in particular that of the hydrogen ion which is a measure of acid strength. Strictly, however, the activity of a single ionic species is not measurable, for positive ions always exist in the presence of negative ions. Nevertheless, the mean activity of HCl which is measurable in a cell does conveniently indicate the mean activity of the ions which carry the current, and —logjQ of this activity is the pH of the solution. The basic principle of potentiometric pH determination may be seen by considering a cell divided into two halves by a silver wall coated on both sides with silver chloride ... 

AI2O3 may be used to increase the hydrophilidty and mechanical strength of hydrophobic membranes such as those made of PVDF (Yan et al. 2006). Ag is a typical antifouling agent, which may be added by an ex situ synthesis method followed by addition to the casting solution, or by an in situ reduction of ionic silver by the polymer solvent (Taurozzi et al. 2008). The bactericidal effect depends on the release of ionic silver from the membrane, which is necessarily limited in time. 

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