Potassium chloride solution

We will focus on one experimental study here. Monovoukas and Cast studied polystyrene particles witli a = 61 nm in potassium chloride solutions [86]. They obtained a very good agreement between tlieir observations and tire predicted Yukawa phase diagram (see figure C2.6.9). In order to make tire comparison tliey rescaled the particle charges according to Alexander et al [43] (see also [82]). At high electrolyte concentrations, tire particle interactions tend to hard-sphere behaviour (see section C2.6.4) and tire phase transition shifts to volume fractions around 0.5 [88]. 

Reference Electrodes and Liquid Junctions. The electrical cincuit of the pH ceU is completed through a salt bridge that usually consists of a concentrated solution of potassium chloride [7447-40-7]. The solution makes contact at one end with the test solution and at the other with a reference electrode of constant potential. The Hquid junction is formed at the area of contact between the salt bridge and the test solution. The mercury—mercurous chloride electrode, the calomel electrode, provides a highly reproducible potential in the potassium chloride bridge solution and is the most widely used reference electrode. However, mercurous chloride is converted readily into mercuric ion and mercury when in contact with concentrated potassium chloride solutions above 80°C. This disproportionation reaction causes an unstable potential with calomel electrodes. Therefore, the silver—silver chloride electrode and the thallium amalgam—thallous chloride electrode often are preferred for measurements above 80°C. However, because silver chloride is relatively soluble in concentrated solutions of potassium chloride, the solution in the electrode chamber must be saturated with silver chloride. 

Anthraquinone-l,5-disulfonic acid [117-14-6] (44), and anthraquinone-1, 8-disulfonic acid [82-48-4] (45) are produced from anthraquinone by disulfonation in oleum a higher concentration of SO than that used for 1-sulfonic acid is employed in the presence of mercury catalyst (64,65). After completion of sulfonation, 1,5-disulfonic acid is precipitated by addition of dilute sulfuric acid and separated. After clarification with charcoal, 1,5-disulfonic acid is precipitated as the sodium salt by addition of sodium chloride. The 1,8-disulfonic acid is isolated as the potassium salt from the sulfuric acid mother hquor by addition of potassium chloride solution. 

Prepared saltwater completion fluids are made of fresh surface water, with sufficient salts added to produce the proper salt concentration. Usually, the addition of 5 to 10% NaCl, 2% CaClj, or 2% KCl is considered satisfactory for clay inhibition in most formations. Sodium chloride solutions have been extensively used for many years as completion fluids these brines have densities up to 10 Ib/gal. Calcium chloride solutions may have densities up to 11.7 lb/ gal. The limitations of CaClj solutions are (1) flocculation of certain clays, causing permeability reduction, and (2) high pH (10 to 10.5) that may accelerate formation clays dispersion. In such cases, CaC12-based completion fluids should be replaced with potassium chloride solutions. Other clear brines can be formulated using various salts over wide range of densities, as shown in Figure 4-123 [28]. 

It has been shown that the charge influences the distribution of the primary corrosion products, and recent work has indicated that the existence of carboxyl groups in the polymer film has an important influence on its behaviour when immersed in potassium chloride solutions. 

The films were then soaked in water and removed from the plates. Portions were mounted in glass cells which were filled with potassium chloride solution two Ag/AgCl electrodes were inserted into the limbs of the cells and the unit was placed in a thermostat. The resistance of the films was determined, from time to time, by connecting the cells in series with a known resistance and applying a potential of 1 V to the combination the potential drop across the standard resistance was measured by means of a valve potentiometer. 

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... 

Fig. 14.2 Relationship between the logarithm of the resistance of D and / Aims of a penta-erythritol alkyd paint, containing 6-1% iron oxide by volume, and the concentration of the potassium chloride solutions in which they were immersed (courtesy Bril. Polym. J., 3, 41...

The discussion so far has been limited to the behaviour of polymer films after immersion in potassium chloride solutions for only a short time. When varnish films were immersed in potassium chloride solutions for a month or more a steady fall in resistance took place. Further experiments indicated that the effect was reversible and dependent on both the pH of the solution and the concentration of potassium chloride. It was concluded that an ion exchange process was operative . 

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. 

In order to examine the effect of solvents, films of a solvent-free epoxypolyamine were cast, mounted in cells and their resistances measured in dilute and concentrated potassium chloride solution . All the films had / properties with resistances in the range 10 -I0 flcm. ... 

An important use of a mercury cathode is in the purification of electrolyte solutions, for example the removal of traces of heavy metals from potassium chloride solutions.-All such impurities have much more positive deposition... 

The most widely used reference electrode, due to its ease of preparation and constancy of potential, is the calomel electrode. A calomel half-cell is one in which mercury and calomel [mercury(I) chloride] are covered with potassium chloride solution of definite concentration this may be 0.1 M, 1M, or saturated. These electrodes are referred to as the decimolar, the molar and the saturated calomel electrode (S.C.E.) and have the potentials, relative to the standard hydrogen electrode at 25 °C, of 0.3358,0.2824 and 0.2444 volt. Of these electrodes the S.C.E. is most commonly used, largely because of the suppressive effect of saturated potassium chloride solution on liquid junction potentials. However, this electrode suffers from the drawback that its potential varies rapidly with alteration in temperature owing to changes in the solubility of potassium chloride, and restoration of a stable potential may be slow owing to the disturbance of the calomel-potassium chloride equilibrium. The potentials of the decimolar and molar electrodes are less affected by change in temperature and are to be preferred in cases where accurate values of electrode potentials are required. The electrode reaction is... 

Some commercial electrodes are supplied with a double junction. In such arrangements, the electrode depicted in Fig. 15.1(h) is mounted in a wider vessel of similar shape which also carries a porous disc at the lower end. This outer vessel may be filled with the same solution (e.g. saturated potassium chloride solution) as is contained in the electrode vessel in this case the main function of the double junction is to prevent the ingress of ions from the test solution which may interfere with the electrode. Alternatively, the outer vessel may contain a different solution from that involved in the electrode (e.g. 3M potassium nitrate or 3M ammonium nitrate solution), thus preventing chloride ions from the electrode entering the test solution. This last arrangement has the disadvantage that a second liquid junction potential is introduced into the system, and on the whole it is preferable wherever possible to choose a reference electrode which will not introduce interferences. 

This electrode is perhaps next in importance to the calomel electrode as a reference electrode. It consists of a silver wire or a silver-plated platinum wire, coated electrolytically with a thin layer of silver chloride, dipping into a potassium chloride solution of known concentration which is saturated with silver chloride this is achieved by the addition of two or three drops of 0.1M silver nitrate solution. Saturated potassium chloride solution is most commonly employed in the electrode, but 1M or 0.1 M solutions can equally well be used as explained in Section 15.1, the potential of the electrode is governed by the activity of the chloride ions in the potassium chloride solution. 

Glass electrodes are now available as combination electrodes which contain the indicator electrode (a thin glass bulb) and a reference electrode (silver-silver chloride) combined in a single unit as depicted in Fig. 15.2(h). The thin glass bulb A and the narrow tube B to which it is attached are filled with hydrochloric acid and carry a silver-silver chloride electrode C. The wide tube D is fused to the lower end of tube B and contains saturated potassium chloride solution which is also saturated with silver chloride it carries a silver-silver chloride electrode E. The assembly is sealed with an insulating cap. 

In an alternative procedure designed to deal with minute volumes of liquid, Walter38 set up a layer cell based upon the technique employed in instant colour photographic films, Such a cell designed to determine potassium ions made use of two layer assemblies terminating in valinomycin electrodes, so that with a standard potassium chloride solution added to one assembly, and the... 

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. 

DETERMINATION OF THE HALF-WAVE POTENTIAL OF THE CADMIUM ION IN 1 (If POTASSIUM CHLORIDE SOLUTION... 

Pipette lOmL of a cadmium sulphate solution (1.0gCd2+ L-1) into a 100 mL graduated flask, add 2,5 mL of 0.2 per cent gelatin solution, 50 mL of 2 M potassium chloride solution and dilute to the mark. The resulting solution (A) will contain 0.100gCd2+ L-1 in a base solution (supporting electrolyte) of 1 M potassium chloride with 0.005 per cent gelatin solution as suppressor. 

Combine 50 g of the air-dried soil with 100 mL of acetone and shake the mixture with a mechanical shaker for 15 min. Filter the mixture through a fluted filter paper into a 500-mL flask. Wash the residue on the filter with 50 mL of acetone. Combine the filtrates and remove acetone by rotary evaporation. Transfer the residue with 150 mL of a potassium chloride solution into a separatory funnel, extract the solution with two portions of 50 mL of dichloromethane and collect the organic extracts in a flask. Filter the combined solvent extracts, together with the washings of the collecting flask, through anhydrous sodium sulfate into a 300-mL flask. Remove dichloromethane by rotary evaporation. Dissolve the residue in 10 mL of carbon tetrachloride. 

The two equations show that the nearer the cationic transport is to 0.5, the smaller is the liquid junction potential (other factors being unchanged). Among common electrolytes one of the highest numerical values of the factor (2 t+ - I) is given by hydrochloric acid, at 0.65. Hence a potential difference of about 39 mV develops at 25 °C across the junction between 0.001 N and 0.01 N hydrochloric acid. In the case of potassium chloride solution,... 

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