KC1 solution

Fe electrodes with electrochemically polished (cathodically pretreated for 1 hr) and renewed surfaces have been investigated in H20 + KF and H20 + Na2S04 by Rybalka et al.721,m by impedance. A diffuse-layer minimum was observed at E = -0.94 V (SCE) in a dilute solution of Na2S04 (Table 19). In dilute KC1 solutions E,njn was shifted 40 to 60 mV toward more negative potentials. The adsorbability of organic compounds (1-pentanol, 1-hexanol, cyclohexanol, diphenylamine) at the Fe electrode was very small, which has been explained in terms of the higher hydro-philicity of Fe compared with Hg and Hg-like metals. 

A diffuse-layer minimum in C,E curves has not been found with electrodes kept 3 min at E = -0.74 V, i.e., at a potential close to the rest potential of Fe.728 Complete cathodic reduction at <<-0.74 V (SCE) is not achieved since a diffuse-layer minimum is not found for cathodically reduced electrodes. This effect has been explained by the oxidation of Fe. According to impedance data, strong specific adsorption of Cl anions at renewed Fe electrodes occurs since a very large shift of Eosq takes place going from KF to KC1 solutions. 

Pour 1.00 mL of the KC1 solution into a clean, dry test tube. 

Making Predictions Assume you did not know the concentration of the silver nitrate solution. How would this unknown concentration compare with the concentration of the KC1 solution if half as much AgN03 solution as KC1 solution was used ... 

Thiessen and Wilson (1987) presented a modified isopiestic apparatus and obtained osmotic coefficient data for KC1 solutions using NaCl as reference solution. The data are given in Table 15.4. Subsequently, they employed Pitzer s method to correlate the data. They obtained the following values for three Pitzer s... 

Figure 1 The solubility of the principal atmospheric gases in seawater, as a function of temperature. Units are millilitres of gas contained in a litre of seawater of salinity 35 psu, assuming an overlying atmosphere purely of each gas. Note that salinity is defined in terms of a conductivity ratio of seawater to a standard KC1 solution and so is dimensionless. The term practical salinity unit , or psu, is often used to define salinity values, however. It is numerically practically identical to the old style unit of parts per thousand by weight...

Another method for obtaining these values is to determine the mobilities of ions, from which the ratio A+ /A" can be calculated. This is based on the measurement of the absolute velocities of the cations and anions under the influence of a potential gradient, as originally suggested by Lodge (1886) and applied later by Masson and many others. For instance, Masson (1899)1 carried out experiments with 10% KC1 solution in gelatine gel, the principle of which is illustrated in Fig. 2.2. 

Although not essential, one often uses a previously coated AgCl-Ag electrode or a silver-plated Pt wire coated electrolytically in KC1 solution with a thin deposit of AgCl. Such dry AgCl-Ag electrodes are much in favour as reference electrodes (although in the absence of oxidants), in addition to calomel electrodes (Pt wire in contact with Hg, covered with calomel paste in contact with KC1 solution), which also belong to the second kind, viz.,... 

Their potentials in 0.1 N, lmolal, IN and saturated KC1 solutions are 0.3337, 0.2800, 0.2897 and 0.2415 V, respectively. The dilute types reach their equilibrium potentials more quickly and these potentials are less dependent on temperature the SCE has the advantage of being less sensitive to current flow (electrolysis). The AgCl-Ag electrodes are more compact, do not need a liquid function, which makes them exceedingly attractive for analysis in non-aqueous media, and support high temperatures. 

As in normal potentiometry one uses and indicator electrode versus a reference electrode, the electrodes should, especially in pH measurements, be those recommended by the supplier of the pH meter in order to obtain a direct reading of the pH value displayed. In redox or other potential measurements any suitable reference electrode of known potential can be applied. However, a reference electrode is only suitable if a junction potential is excluded, e.g., an Ag-AgCl electrode in a solution of fixed Ag+ concentration or a calomel electrode in a saturated KC1 solution as a junction in many instances a direct contact of Cl" with the solution under test (possibly causing precipitation therein) is not allowed, so that an extra or so-called double junction with KN03 solution is required. Sometimes micro-electrodes or other adaptations of the surface are required. 

As a new rule of thumb [473], in 0.15 M NaCl (or KC1) solutions titrated with NaOH (or KOH), acids start to precipitate as salts above log (S/So) 4 and bases above log (S/.S o) 3. It is exactly analogous to the cliff 3-4 rule let us call the solubility equivalent the sdijf3-4 rule [473], Consider the case of the monopro-tic acid HA, which forms the sodium salt (in saline solutions) when the solubility product Ksp is exceeded. In additions to Eqs. (3.1) and (6.1), one needs to add the following reaction/equation to treat the case ... 

Figure 6.7 Dissolution template titration (DTT) curve of propoxyphene 0.51 mg of the hydrochloride salt was dissolved in 5.1 mL of 0.15 M KC1 solution, with 0.0084 mL of 0.5 M KOH used to raise the pH to 10.5.

The dependence of ion-pairing on the dielectric constant is illustrated in the following example. The formation of K+C1" ion pairs in aqueous KC1 solutions has not been demonstrated. In methanol (D = 32.6), for KC1,... 

Burgmayer and Murray [40] reported electrically controlled resistance to the transport of ions across polypyrrole membrane. The membrane was formed around a folded minigrid sheet by the anodic polymerization of pyrrole. The ionic resistance, measured by impedance, in 1.0 M aqueous KC1 solution was much higher under the neutral (reduced) state of the polymers than under the positively charged (oxidized) state. The redox state of polypyrrole was electrochemically controlled this phenomenon was termed an ion gate, since the resistance was varied from low to high and vice versa by stepwise voltage application. 

Even very small amounts of calcium provide a desirable decrease in the Na/Ca ratio. Prior studies indicating potassium chloride totally negates permeability reduction may have utilized water that contained some small amount of calcium ion to measure KC1 solution permeability. A second factor, which might explain the lack of KC1 damage reported in prior studies is a low ionic concentration, especially calcium, in the water used to equilibrate the cores prior to the KC1 tests. 

Fig. 13.15 Frequency dependence of broad band SL spectra from argon-saturated KC1 solutions. The ultrasonic frequencies used are 28, 48, 115 kHz and 1.0 MHz (from bottom to top) [42] (Reprinted from the Institute of Electronics, Information and Communication Engineers. With permission)...

Figure 4. Cyclic voltammograms at Pt-treated Ti02 (a) and Ti02 (b) electrodes in a C02-saturated 0.5 M KC1 solution at 40°C.87 Scan rate 0.05 V/s.

Bang s reagent (for glucose estimation) dissolve 100 g of K2C03, 66 g of KC1, and 160 of KHCOj in the order given in about 700 mL of water at 30°C. Add 4.4 g of copper sulfate and dilute to 1 liter after the C02 is evolved. This solution should be shaken only in such a manner as not to allow the entry of air. After 24 hours 300 mL diluted to a liter with saturated KC1 solution, shaken gently and used after 24 hours 50 mL = 10 mg glucose. 

We assume a 0.1 molal KC1 solution containing hypothetical amounts of silica, aluminum, and carbonate. We set temperature to 200 °C and run the calculation... 

A basic electrochemical cell is depicted in Figure 9.3 and is made of a copper wire in one container with a solution of copper sulfate and a zinc rod in a different container with a zinc sulfate solution. There is a salt bridge containing a stationary saturated KC1 solution between the two containers. Electrons flow freely in the salt bridge in order to maintain electrical neutrality. A wire is connected to each rod and then to a measuring device such as a voltmeter to complete the cell. 

Most common reference electrodes are silver-silver chloride (SSC), and saturated calomel electrode (SSC, which contains mercury). The reference electrode should be placed near the working electrode so that the W-potential is accurately referred to the reference electrode. These reference electrodes contain concentrated NaCl or KC1 solution as the inner electrolyte to maintain a constant composition. Errors in electrode potentials are due to the loss of electrolytes or the plugging of the porous junction at the tip of the reference electrode. Most problems in practical voltammetry arise from poor reference electrodes. To work with non-aqueous solvents such as acetonitrile, dimethylsulfoxide, propylene carbonate, etc., the half-cell, Ag (s)/AgC104 (0.1M) in solvent//, is used. There are situations where a conventional reference electrode is not usable, then a silver wire can be used as a pseudo-reference electrode. 

The electrodes described in this section are commercially available. The body of these electrodes may be either glass or epoxy plastic, as we have discussed. Epoxy plastic electrodes are unbreakable. Some electrodes are gel-filled electrodes and are sealed. This means that the KC1 solution has a gelatin mixed with it. There is no vent hole, they cannot be refilled with saturated KC1, and solid KC1 cannot be added. 

Spectra of KC1 solutions (reference) were subtracted from spectra of aqueous organic solutions (sample), both at the same pH value and both previously ratioed against the empty cell spectrum, to yield aqueous solution spectra of the organic compounds. 

Sb carrier ions. The Sb-119 ions were adsorbed on 30 mg of hematite from 10 cm3 of a 0.25 mol/dm3 KC1 solution containing about 1 mg of pentavalent Sb ions. About 0.3 mg of Sb was adsorbed at pH 2.5 and 4.0. The amounts of Sb adsorbed are less than that required to cover all the hematite surfaces as a monolayer. The emission Mossbauer spectra obtained are shown in Figure 7. It is seen from Figure 7 that the width of the emission Mossbauer spectrum at pH 2.5 is much smaller than that of the carrier-free one, while essentially no effect of carrier Sb ions is observed at pH 4.0. 

Effects of Pentavalent Sb Ions on the Adsorption of Divalent Co-57 on Hematite. Benjamin and Bloom reported that arsenate ions enhance the adsorption of cobaltous ions on amorphous iron oxyhydroxide (J 6). Similarly, when divalent Co-57 ions were adsorbed on hematite together with pentavalent Sb ions, an increase of adsorption in the weakly acidic region was observed. For example, when 30 mg of hematite was shaken with 10 cm3 of 0.1 mol/dm3 KC1 solution at pH 5.5 containing carrier-free Co-57 and about 1 mg of pentavalent Sb ions, 95 % of Co-57 and about 30 % of Sb ions were adsorbed. The emission spectra of the divalent Co-57.ions adsorbed under these conditions are shown in Figure 8 together with the results obtained under different conditions. As seen in Figure 8, the spectra of divalent Co-57 co-adsorbed with pentavalent Sb ions are much different from those of Co-57 adsorbed alone (Figure 3). These observations show a marked effect of the.co-adsorbed pentavalent Sb ions on the chemical structure of adsorbed Co-57. 

Figure 7. In situ emission Mossbauer spectra of pentavalent Sb-119 adsorbed on hematite with Sb carrier from 0.25 mol/dm3 KC1 solution (A) pH 4.0 and (B) 2.5.

In this study we have examined recrystallization in the KCl-KBr-H20 system at 25°C (8). The solubilities of the end-members KC1 and KBr were determined from both oversaturation and undersaturation. In studying the solubility of this solid solution system, solubility experiments were carried out in pairs (8). For each pair of experiments (A and B), the total amounts of KC1 and KBr in the system were identical. In the A-type runs (Table I), solid KC1 was added to an initial KBr aqueous solution, and in the B-type runs, solid KBr was added to an initial aqueous KC1 solution. For each pair of runs the total number of moles of KC1 and KBr were identical. The final composition of the solid and aqueous solution was, therefore, approached from two different compositional reaction paths. 

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