Conductivity, electrical 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. 

The water solutions of some substances conduct electricity, while the solutions of others do not. The conductivity of a solution depends on its solute. The more ions a solution contains, the greater its conductivity. Solutions that conduct electricity are called electrolytes. Solutions which are good conductors of electricity are known as strong electrolytes. Sodium chloride, hydrochloric acid, and potassium hydroxide solutions are examples of strong electrolytes. If solutions are poor conductors of electricity, they are called weak electrolytes. Vinegar, tap water, and lemon juice are examples of weak electrolytes. Solutions of substances such as sugar and alcohol solutions which do not conduct electricity are called nonelectrolytes. 

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. 

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). 

He foimd that a mixture of diethylzinc and ethylsodium forms a solution which is not inferior to 0.1 N aqueous potassium chloride solution in electrical conductivity. In this case the existence of electrical conductivity is explained by the formation of the dissociating complex ... 

With the decrease in permittivity, however, complete dissociation becomes difficult. Some part of the dissolved electrolyte remains undissociated and forms ion-pairs. In low-permittivity solvents, most of the ionic species exist as ion-pairs. Ion-pairs contribute neither ionic strength nor electric conductivity to the solution. Thus, we can detect the formation of ion-pairs by the decrease in molar conductivity, A. In Fig. 2.12, the logarithmic values of ion-association constants (log KA) for tetrabutylammonium picrate (Bu4NPic) and potassium chloride (KC1) are plotted against (1 /er) [38]. 

Other physical phenomena that may be associated, at least partially, with complex formation are the effect of a salt on the viscosity of aqueous solutions of a sugar and the effect of carbohydrates on the electrical conductivity of aqueous solutions of electrolytes. Measurements have been made of the increase in viscosity of aqueous sucrose solutions caused by the presence of potassium acetate, potassium chloride, potassium oxalate, and the potassium and calcium salt of 5-oxo-2-pyrrolidinecarboxylic acid.81 Potassium acetate has a greater effect than potassium chloride, and calcium ion is more effective than potassium ion. Conductivities of 0.01-0.05 N aqueous solutions of potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, sodium carbonate, potassium bicarbonate, potassium hydroxide, and sodium hydroxide, ammonium hydroxide, and calcium sulfate, in both the presence and absence of sucrose, have been determined by Selix.88 At a sucrose concentration of 15° Brix (15.9 g. of sucrose/100 ml. of solution), an increase of 1° Brix in sucrose causes a 4% decrease in conductivity. Landt and Bodea88 studied dilute aqueous solutions of potassium chloride, sodium chloride, barium chloride, and tetra-... 

A solute may be present as ions or as molecules. We can identify the form of the solute by noting whether the solution conducts an electric current. Because a current is a flow of electric charge, only solutions that contain ions conduct electricity. There is such a tiny concentration of ions in pure water (about 10-7 m) that water alone does not conduct electricity. A substance that dissolves to give a solution that conducts electricity is called an electrolyte. Electrolyte solutions (solutions of electrolytes), which conduct electricity because they contain ions, include aqueous solutions of ionic compounds, such as sodium chloride and potassium nitrate. The ions are not formed when an ionic solid dissolves they exist as separate ions in the solid but become free to move apart in the presence of water (Fig. 1.1). Acids also are electrolytes. Unlike salts, they are molecular compounds in the pure state but form ions when they dissolve. One example is hydrogen chloride, which exists as gaseous HC1 molecules. In solution, however, HCl is called hydrochloric acid and is present as hydrogen ions and chloride ions. 

Potassium Nitrosochlor-ruthenate or Potassium Ruthenium Ni-trosochloride, 2KC1. RuCl3. XO or K2RuClsNO, is obtained by direct precipitation of concentrated solutions of potassium chloride and ruthenium nitrosochloride it also results on evaporation of mixed dilute solutions of the two substances.3 It yields black orthorhombic crystals which dissolve in water to a reddish violet solution. The aqueous solution is stable, its electric conductivity showing no alteration whatever after standing for two weeks. Its solution apparently contains three ions,4 namely, K , K and RuCls.XO". 

Many properties of electrolytic solutions are additive functions of the properties of the respective ions this is at once evident from the fact that the chemical properties of a salt solution are those of its constituent ions. For example, potassium chloride in solution has no chemical reactions which are characteristic of the compound itself, but only those of potassium and chloride ions. These properties are possessed equally by almost all potassium salts and all chlorides, respectively. Similarly, the characteristic chemical properties of acids and alkalis, in aqueous solution, are those of hydrogen and hydroxyl ions, respectively. Certain physical properties of electrolytes are also additive in nature the most outstanding example is the electrical conductance at infinite dilution. It will be seen in Chap. II that conductance values can be ascribed to all ions, and the appropriate conductance of any electrolyte is equal to the sum of the values for the individual ions. The densities of electrolytic solutions have also been found to be additive functions of the properties of the constituent ions. The catalytic effects of various acids and bases, and of mixtures with their salts, can be accounted for by associating a definite catalytic coefl5.cient with each type of ion since undissociated molecules often have appreciable catalytic properties due allowance must be made for their contribution. 

Problem Salts are substances, which are composed of ions - because of their charge the ions are capable of moving in an electrical field. But the ions are statically built into solid crystal and cannot move no conductivity can be ascertained at room temperature. As soon as a big crystal is strongly heated the ions become movable. This can be proven by using conductivity measurements. In melt and solutions, the ions are quite movable electric conductivity results. Because sodium chloride has the very high melting temperature of 800°C, a mixture of lithium chloride and potassium chloride are molten together and used. 

The surface area of the electrodes and their arrangement in the conductometric cell influence the electric resistance via the quotient l/A, the so-called cell constant. However, these geometric quantities are often difficult to investigate, especially in the case of platinated electrodes. Therefore, the cell constant is determined by using a calibrating solution of known a value (usually a solution of potassium chloride). These days, commercial equipment for measuring conductivity (conductometer) is... 

Next, it defines the practical salinity S in terms of the ratio Kjs of the specific electrical conductivity (hereafter termed conductivity) of seawater to that of a reference potassium chloride (KCl) solution, both at a temperature of 15 °C and under a pressure of one standard atmosphere ... 

The definitions of 1902 and 1969 give identical results at a salinity of 35 %o and do not differ significantly for most applications. The definition of salinity was reviewed again when techniques to determine salinity from measurements of conductivity, temperature, and pressure were developed. The Practical Salinity Scale defined in 1978 is a complex function related to the ratio (K) of the electrical conductivity of a seawater sample to that of a potassium chloride (KCl) solution with a mass fraction in KCl of 0.0324356, at the same temperature and pressure. 

The practical salinity, symbol S, of a sample of sea water, is defined in terms of the ratio K of the electrical conductivity of a sea water sample of 15°C and the pressure of one standard atmosphere, to that of a potassium chloride (KCl) solution, in which the mass fraction of KCl is 0.0324356, at the same temperature and pressure. The K value exactly equal to one corresponds, by definition, to a practical salinily equal to 35. 

Many aqueous solutions, especially those of organic substances (sugar, glycerol, alcohol), are also poor conductors of electricity. But many other aqueous solutions conduct an electric current very well These include solutions of most acids (hydrochloric acid, acetic acid, etc.), bases (sodium hydroxide, calcium hydroxide, etc.) and salts (sodium chloride, potassium sulfate, etc.). 

Tin trimethyl hydroxide is isolated from the iodide by action of potassium hydroxide. It crystallises in prisms and is volatile iii steam. The aqueous solution is strongly alkaline, and the solubility in alcohol is greater than in water. With tin trimethyl halides it forms complexes of the type (Me jSnOH)2.Me jSnX, the bromide melting at 113° to 115° C. with decomposition iodide 143° to 153° C. with decomposition also the type Me SnOH.MejjSnX.HgO, the chloride M.pt. 90° C. bromide, M.pt. 210° to 211° C. with decomposition iodide, M.pt. 221° C. with decomposition. The electrical conductivity of solutions of the hydroxide has been determined by Bredig.-... 

An electrochemical cell consists of two conductors called electrodes, each of which is immersed in an electrolyte solution. In most of the cells that will be of interest to us, the solutions surrounding the two electrodes are different and must be separated to avoid direct reaction between the reactants. The most common way of avoiding mixing is to insert a salt bridge, such as that shown in Figure 18-2, between tire solutions. Conduction of electricity from one electrolyte solution to the other then occurs by migration of potassium ions m the bridge in one direction and chloride ions in the other. However, direct contact between copper metal and silver ions is prevented. 

In order to minimize electricity consumption, it is important to choose an electrolyte of maximum conductivity. Usually, a concentrated aqueous solution of potassium hydroxide (30-40 wt.%) is employed. This must be prepared from very pure water, otherwise impurities will accumulate during electrolysis the chloride ion, which is usually present in water, is particularly harmful in that it causes pitting of the protective films formed on metal surfaces in alkaline solutions. 

The name given to a substance which when dissolved in water enables the resulting solution to conduct an electric current. The most common electrolytes in the human body are salts of such minerals as sodium, potassium, magnesium, calcium, phosphate, sulfate, and chloride. 

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