Transference number of potassium chloride

TABLE XXVIH. TRANSFERENCE NUMBERS OF POTASSIUM CHLORIDE SOLUTIONS AT 25 ... 

The data obtained by Machines and Dole11 in a series of measurements of the transference numbers of potassium chloride are given in Table I. The tabic is largely self-explanatory. Two figures for a... 

Table III. The Influence of the Volume Correction in the Determination of the Transference Number of Potassium Chloride...

An illustrative computation from Des Coudres results is as follows. He found 0.510 x 10 volt for the ratio E/h for 2.71 molal potassium chloride. Multiplying the product EF/h by 101 to reduce it to absolute units, and dividing by the value 980.7, also in absolute units, for g, the acceleration due to gravity, yields 5.02 grams. The values of the other terms in equation (8a) are Voi, = 18.36 cc., t aci - 31.3 cc. and p = 1.111. From these figures and the molecular weights equation (8a) gives the value 0.50 for the cation transference number of potassium chloride. If the same values of the transference number are obtained as are found by other methods it is evident that a correct analysis of the mechanism of the process has been made. Such a comparison is made in Table I. The values of the... 

A short review of the assumptions made in obtaining equation (23) is sufficient to indicate the uncertainty involved in this type of computation. It has been assumed (a) that the boundary is of a mixture type, (b) that the mobilities are constant throughout the concentration range to 4.2 normal and (c) that the ions are normal solutes. All these assumptions, as has been shown in preceding pages, are contrary to fact. Furthermore the difference between the mobilities of potassium and chloride ions is not as small as it was thought to be until recently. This is indicated by the fact that the transference number of potassium chloride,... 

The solid solution KCl-RbCl differs basically from the solid solution NiO-MgO in two ways. Firstly, the system KCl-RbCl exhibits purely ionic conduction. The transport numbers of electronic charge carriers are negligibly small. Secondly, a finite transport of anions occurs. Because of these facts, the atomic mechanism of the solid state reaction between KCl and RbCl is essentially of a different sort than that between NiO and MgO. Once again, the diffusion profile exhibits an asymmetry (see Fig. 6-1). However, in this case the asymmetry arises not so much because of the variation of the defect concentration with composition, but rather because of the different mobilities of the ions at given concentration. Were the transport number of the chloride ions negligible, then the diffusion potential (which would be set up because of the different diffusion velocities of potassium and rubidium) would ensure that the motion of the two cations is coupled. If, on the contrary, the transference number of the chloride ions is one, then there is no diffusion potential, and the motion of the two cations is decoupled. 

To work out the formula of an ionic compound using Lewis symbols, we first represent the cation by removing the dots from the symbol for the metal atom. Then we represent the anion by transferring those dots to the Lewis symbol for the nonmetal atom to complete its valence shell. We may need to adjust the numbers of atoms of each kind so that all the dots removed from the metal atom symbols are accommodated by the nonmetal atom symbols. Finally, we write the charge of each ion as a superscript in the normal way. A simple example is the formula of potassium chloride ... 

As the transference number of the OH-ions formed by dissociation of potassium hydroxide is lower than that of sodium hydroxide ) it is obvious from equation (XI-24) that the yields obtained on electrolysis of potassium chloride... 

If it is required to determine the transference numbers of the ions constituting the electrolyte MA, e.g., potassium chloride, by the moving boundary method, it may be supposed that two other electrolytes, designated by M A and MA, e.g., lithium chloride and potassium acetate, each having an ion in common with the experimental solute MA, arc available to act as indicators.Imagine the solution of MA to be placed between the indicator solutions so as to form sharp boundaries at a and 5, as shown in Fig. 41 the anode is inserted in the. solution of M A and the cathode in that of MA. In order that the boundaries... 

It would appear, therefore, that the actual concentration of the indicator solution employed in transference measurements is immaterial experiments show, however, that automatic attainment of the Kohl-rausch regulating condition is not quite complete, for the transference numbers have been found to be dependent to some extent on the concentration of the bulk of the indicator solution. This is shown by the results in Fig. 42 for the observed transference number of the potassium ion in 0.1 n potassium chloride, with lithium chloride of various concentrations as indicator solution. The concentration of the latter required to satisfy equation (15) is 0.064 n, and hence it appears, from the constancy of the transference number over the range of 0.055 to 0.075 N lithium chloride, that automatic adjustment occurs only when the actual concentration of the indicator solution is not greatly different from the Kohl-... 

Results of Transference Number Measurements.—Provided the measurements are made with great precision, the results obtained by the Hittorf and moving boundary methods agree within the limits of experimental error this is shown by the most accurate values for various solutions of potassium chloride at 25° as recorded in Table XXVIII. 

Macinnes and Dole [/. Am, Chem, Soc, 53, 1357 (1931)] electrolyzed a 0.5 N solution of potassium chloride, containing 3.6540 g. of salt per 100 g. solution, at 25 using an anode of silver and a cathode of silver coated with silver chloride. After the passage of a current of about 0.018 amp. for approximately 26 hours, 1.9768 g. of silver were deposited in a coulometer in the circuit and on analysis the 119.48 g. of anode solution were found to contain 3.1151 g. potassium chloride per 100 g. solution, while the 122.93 g. of cathode solution contained 4.1786 g. of salt per 100 g. Calculate the values of the transference number of the potassium ion obtained from the anode and cathode solutions, respectively. 

The theoretical basis of the use of a bridge containing a concentrated salt solution to eliminate liquid junction potentials is that the ions of this salt are present in large excess at the junction, and they consequently carry almost the whole of the current across the boundary. The conditions will be somewhat similar to those existing when the electrolyte is the same on both sides of the junction. When the two ions have approximately equal conductances, i.e., when their transference numbers are both about 0.5 in the given solution, the liquid junction potential will then be small [cf. equation (36a)]. The equivalent conductances at infinite dilution of the potassium and chloride ions are 73.5 and 76.3 ohins cm. at 25, and those of the ammonium and nitrate ions are 73.4 and 71.4 ohms cm. respectively the approximate equality of the values for the cation and anion in each case accounts for the efficacy of potassium chloride and of ammonium nitrate in reducing liquid junction potentials. 

Solar evaporation, from primary and secondary ponds of 100 and 30 km in extent, the initial stage for potassium chloride recovery from the Dead Sea brines [26]. The smaller number of constituent ions present in these waters significantly simplifies salts recovery, and the fact that they contain nearly twice the relative potassium chloride concentration of seawater also improves profitability. Developed from a process, which was first operated in 1931, evaporation in the first pond reduces the volume of the brine to about one-half of the initial volume and brings down much of the sodium chloride together with a small amount of calcium sulfate (Fig. 6.5). The concentrated brines are then transferred to the secondary pond where evaporation of a further 20% of the water causes carnallite (KCl MgCli 6H2O) and some further sodium chloride to crystallize out. With care, a 95% potassium chloride product on a scale of some 910,000 tonne/year is obtained either by countercurrent extraction of the carnallite with brines, or by hot extraction of potassium chloride from the sylvinite matrix followed by fractional crystallization for its eventual recovery [16]. 

The Transference Numbers of Ion Constituents in Mixtures of Electrolytes. The moving boundary method can in certain cases be used to determine the transference numbers of the ion constituents in mixtures of electrolytes. The method used by Longsworth 32 for determining the transference numbers in mixtures of hydrochloric acid and potassium chloride is as follows. 

Table VI. Transference Numbers of Ions in Aqueous Hydrochloric Acid-Potassium Chloride Mixtures at 25°...

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 most frequently used method for the preparation of isoquinoline Reissert compounds is treatment of an isoquinoline with acyl chloride and potassium cyanide in water or in a dichloromethane-water solvent system. Though this method could be successfully applied in a great number of syntheses, it has also some disadvantages. First, the starting isoquinoline and the Reissert compound formed in the reaction are usually insoluble in water. Second, in the case of reactive acyl halides the hydrolysis of this reaction partner may became dominant. Third, the hydroxide ion present could compete with the cyanide ion as a nucleophile to produce a pseudobase instead of Reissert compound. To decrease the pseudobase formation phase-transfer catalysts have been used successfully in the case of the dichloromethane-water solvent system, resulting in considerably increased yields of the Reissert compound. To avoid the hydrolysis of reactive acid halides in some cases nonaqueous media have been applied, e.g., acetonitrile, acetone, dioxane, benzene, while utilizing hydrogen cyanide or trimethylsilyl cyanide as reactants instead of potassium cyanide. 

The major ions in different organs and body fluids of euryhaline fish have been studied by a number of authors. The concentrations of sodium, potassium, magnesium and chloride were usually more concentrated in fish taken from sea water than in those from fresh water, the effect being shown in blood, kidney, liver, various secondary muscles and urine. The trend was less clear in the case of swimming muscle, as were the values for calcium (reviewed by Love, 1970, Table 30). All the ions mentioned above were much more concentrated in the urine of the fish from the sea, urine being one channel by which these salts are excreted. A fish with remarkable ability to control its internal milieu is the tilapia, in which the total sodium in the body increases by only 30% when it is transferred from fresh water to doublestrength sea water (Potts et al., 1967). 

The accuracy of the ORP measurements depends on the temperature at which a measurement is taken. For solutions with reactions involving hydrogen and hydroxyl ions, the accuracy also depends on the pH of the water. In natural waters, many redox reactions occur simultaneously each reaction has its own temperature correction depending on the number of electrons transferred. Because of this complexity, some of the field meters are not designed to perform automatic temperature compensation. The temperature correction for such meters may be done with a so-called ZoBell s solution. It is a solution of 3 x 10 3 mole (M) potassium ferrocyanide and 2 x 10 2 M potassium ferricyanide in a 0.1 M potassium chloride solution. The Eh variations of the ZoBell s solution with temperature are tabulated for reference, and the sample Eh is corrected as follows ... 

The Moving Boundary Method for Determining Transference Humbers. A means of obtaining transference numbers which has proved, in recent years, to be of greater precision than the Hittorf procedure is the method of moving boundaries. The phenomenon which makes the measurements possible is as follows. If a potassium chloride solution is placed in a tube above a cadmium chloride solution, as is shown in Fig. 4a, and electric current is passed in the direction indi-... 

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