Potassium chloride solutions, conductance

When samples of about 1 cm were taken from a single cast film of 100 X 200 mm of a number of paint and varnish films, their resistances varied with the concentration of potassium chloride solution in one of two ways (Fig. 14.2). Either the resistance increased with increasing concentration of the electrolyte (inverse or / conduction) or the resistance of the film followed that of the solution in which it was immersed (direct or D conduction). The percentage of / and D samples taken from different castings varied, but average values for a number of castings were 50% D for the pentaerythritol alkyd and the tung oil phenol formaldehyde varnishes, 57% for urethane alkyd, 76% for epoxypolyamide and 78% for polyurethane varnishes... 

The phenomenon of ion exchange has been confirmed by chemical analysis Films were exposed to potassium chloride solutions of increasing pH, ashed and their potassium content determined by flame photometry. It was found that the potassium content of the films increased as the pH of the solutions rose until saturation was reached at a value which corresponded to that of the change-over in the mechanism of conduction. It was concluded that the change-over in the mechanism of conduction corresponded to the point at which the exchange capacity of the film had reached its limit. 

Reference electrodes are usually a calomel or a silver-silver chloride electrode. It is advisable that these be of the double-junction pattern so that potassium chloride solution from the electrode does not contaminate the test solution. Thus, for example, in titrations involving glacial acetic acid as solvent, the outer vessel of the double junction calomel electrode may be filled with glacial acetic acid containing a little lithium perchlorate to improve the conductance. 

TABLE 6.6 Specific Conductivity of Standard Potassium Chloride Solution, in ft-1 cm-1, for Cell Constant Determination... 

A conductance cell having a constant k of 2.485 cm is filled with 0.01 N potassium chloride solution at 25°C the value of A for this solution is 141.2 S... 

The potassium chloride solutions employed in the most recent work contain 1.0, 0.1 or 0.01 mole in a cubic decimeter of solution at 0 , i.e., 0.999973 liter these solutions, designated as 1.0 d, 0.1 d and 0.01 d, where d stands for demal, contain 76.627, 7.4789 and 0.74625 grams of potassium chloride to 1000 grams of water, respectively. The specific conductances of these solutions at 0 , 18 and 25 are quoted in Table VII 2 the particular solution chosen for calibrating a given cell depends... 

As a general rule increase of temperature increases the equivalent conductance both at infinite dilution and at a definite concentration the conductance ratio, however, usually decreases with increasing temperature, the effect being greater the higher the concentration. These conclusions are supported by the results for potassium chloride solutions in Table XI taken from the extensive measurements of Noyes and his... 

TABLE XI. VARIATION OF CONDUCTANCE RATIO OP POTASSIUM CHLORIDE SOLUTIONS... 

Culkin F. and Smith N. D. (1980) Determination of the concentration of potassium chloride solution having the same electrical conductivity at 15 °C and infinite frequency as standard seawater of salinity 35.000% (Chlorinity 19.37394). lEEEJ. Ocean. Eng. OE-5, 22-23. 

Under the prerequisite that the cell constant and the equivalent ionic conductances of eluent anions and eluent cations are known, Eq. (181) makes it possible to calculate the conductivity of typical eluents for this kind of detection method. To determine the cell constant, the conductance of a potassium chloride solution with defined concentration is usually measured, as the equivalent ionic conductances of potassium and chloride ions are known with 74 S cm2 vaf1 and 76 S cm2 val-1, respectively (see Table 6-1). 

Values of/x = Ac/A may be calculated from Kohlrausch s measurements of electrical conductivity of hydrochloric acid solutions. /h and fci can be evaluated from the potentiometric measurements on hydrochloric acid solutions performed by Scatchaed. These data are very reliable since the concentration chain was so arranged as to eliminate diffusion potentials. In this way, ScATCHARD determined the mean activity coefficient V/h/ci instead of the individual ion activities. If we assume that in a potassium chloride solution/ = /ci— which is plausible when we recall that both ions have the same structure—and that fci is the same in hydrochloric acid solutions and potassium chloride solutions of the same concentration, then we can calculate/h and fci in hydrochloric acid solutions. Naturally these values are not strictly correct since the effect of the potassium ions on the activity of the chloride ions probably is different from that of the hydrogen ions at the same ionic strength. In the succeeding table are given values of /x, /h, and fci calculated by the above method. 

Since, however, previous determinations of the specific conductances of the potassium chloride solutions used in calibrating cells were not in complete agreement, Jones and Bradshaw10 have redetermined the values of those constants for some of the more important solutions, using a different method from the one just described. Instead of using... 

Table I. Specific Conductances of Standard Potassium Chloride Solutions...

Consider a cell composed of two ideal nonpolarizable electrodes, for example, two SCEs immersed in a potassium chloride solution SCE/KCl/SCE. The i-E characteristic of this cell would look like that of a pure resistance (Figure 1.3.8), because the only limitation on current flow is imposed by the resistance of the solution. In fact, these conditions (i.e., paired, nonpolarizable electrodes) are exactly those sought in measurements of solution conductivity. For any real electrodes (e.g., actual SCEs), mass-transfer and charge-transfer overpotentials would also become important at high enough current densities. 

This table presents recommended electrolytic conductivity (i<) values for aqueous potassium chloride solutions with molalities of 0.01 mol/kg, 0.1 mol/kg and 1.0 mol/kg at temperatures from 0°C to 50°C. The values, which are based on measurements at the National Institute of Standards and Technology, provide primary standards for the calibration of conductivity cells. The measurements at 0.01 and 0.1 molal are described in Reference 1, while those at 1.0 molal are in Reference 2. Temperatures are given on the lTS-90 scale. The uncertainty in the conductivity is about... 

Other properties of algin reported include conductivity (252 253), contact angles of various solvents on different metal alginate films 175), depolymerization rates for alginic acid in various acids (251, 25U, 255), a pK of 2.95 for the dissociation constant of alginic acid in normal potassium chloride solution (208), absorption spectra of algin (202), and properties determined in connection with molecular weight studies, such as sedimentation and diffusion velocity and partial specific volumes (209),... 

Table 5.2. Specific Conductances of Potassium Chloride Solutions for the Determination of Cell Constants... 

The saturated calomel electrode (SCE) is composed of metalhc mercury in contact with a saturated solution of mercurous chloride, or calomel (Hg2Cl2). A Pt wire in contact with the metallic Hg conducts electrons to the external circuit. The mercurous ion concentration of the solution is controlled through the solubility product by placing the calomel in contact with a saturated potassium chloride solution. It is the saturated KCl solution that gives this electrode the saturated name there are other calomel reference electrodes used that differ in the concentration of KCl solution, but all contain saturated mercurous chloride solution. A typical calomel electrode is shown in Fig. 15.5. The half-cell... 

This table presents recommended electrolytic conductivity (K) values for aqueous potassium chloride solutions with molalities of 0.01 mol/kg,... 

Two stable states in frog node of Ranvier in 20 0 in 0.5 M potassium chloride solutions are observed by Stampfli [46]. Similar phenomena are also observed in the case of squid action membrane [46, 47]. It should be noted that the biological phenomena could be correlated with the generation of action potential. The value of conductance of membrane when filled with the solutions in the two steady states is given in Table 8.3. 

Weast et al. (1961), who reviewed the corrosion of zinc in dilute aqueous solutions and zinc potentials, obtained linear relationships between corrosion weight loss and time of immersion at various temperatures in the 50-80°C range in water containing 1(X) mg/L of potassium chloride and under pressure. The zinc corrosion products formed at SS C are about 1000 times more electrically conductive than those produced at 25 C. Grubitsch (1969) has also looked at potential in sodium sulfate. They did not observe the maximum at 60°C found in distilled water (see later). It was proposed that the maximum is a characteristic of corrosion in dilute aqueous solutions at atmospheric pressure, where air or oxygen can escape from the solution. The direct dependence of corrosion rate on the oxygen concentration above the dilute potassium chloride solutions at 51°C was shown a half-century ago by Kenworthy and Smith (Fig. 3.3). 

To illustrate the relation between transference numbers and conductivity, the transport number of potassium in dilute potassium chloride solution is used to find the limiting ionic conductivity. On extrapolation to infinite dilution, the molar conductivity of aqueous potassium chloride solution is found to be 149.85 S cm moE (11). From equation (20.1.2-14) and the value for found in Section 20.2.3 ... 

The remaining molar conductivity of the potassium chloride solution can be attributed to the chloride anion if one neglects the contribution arising from the auto-ionisation of water. Hence, the limiting ionic conductivity of the chloride anion is 76.42 S cm moE. ... 

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