Determination by electrical conductivity

The solubility of the former (determined by electrical conductivity measurements) was i8-2 millimoles per litre for particles of a radius a = 00003 cm., and 15 33 millimoles for particles of a radius a = 0002 cm., so that the smaller particles show a considerably larger solubility. Since the osmotic pressures are proportional to the amounts dissolved, we can write... 

The value for KeQ, determined by electrical-conductivity measurements of pure water, is 1.8 X 10-16 m at 25 °C. Substituting this value for Ke[Pg.61]

Electrolytes, depending upon their strength, dissociate to a greater or less extenl in polar solvents. The extent to which a weak electrolyte dissociates may be determined by electrical conductance, electromotive force, and freezing point depression methods. The electrical conductance method is the most used because of its accuracy and simplicity. Arrhenius proposed that the degree of dissociation, a. of a weak electrolyte at any concentration in solution could be found from the rutio of the equivalent conductance. A. of the electrolyte at the concentration in question to (he equivalent conductance at infinite dilution A0 of the electrolyte. Thus... 

Potassium chlor-ruthenite rapidly hydrolyses in aqueous solution, the liquid, originally red. gradually becoming black. The velocity of the hydrolysis admits of determination by electric conductivity measurements in consequence of the hydrochloric acid set free.2... 

Bader et al. (1988) used common salt as a solid tracer, which was injected into a flowing catalyst bed. Solids samples, withdrawn downstream of tracer injection, were leached with water and the salt concentration determined by electrical conductivity of the solution. Their results indicated substantial solids backmixing. Li et al. (1991) observed solids mixing in a fast fluidized bed combustor by using raw coal as a tracer, which was injected into the ash bed. Their results also showed that near-perfect mixing prevailed. Similar experiments was also conducted by Chesonis et al. (1991) in a cold model. 

Materials. Dodecylpyridinium bromide was synthesized by treating fractionally distilled 1-dodecane bromide in dry pyridine for 12 hr. The crude surfactant was recrystallized twice from acetone followed by decolorization with active charcoal in methanol solution. The resulting white crystal is a monohydrate of DoPBr. The critical micelle concentration (CMC) in aqueous solution as determined by electric conductivity method is 17.4 mM at 30°C in agreement with literature. Calf thymus DNA (sodium salt, SIGMA) was used as received. Residual (nucleotide) concentration was determined by a colloid titration using poly(potassium vinyl sulfate) as a titrant and Toluidine Blue as an indicator. 4 Propionyl- a-cyclodextrin (prop- a-CD) used as a neutral carrier was prepared by esterification of a-cyclodextrin (Tokyo Kasei Co.) with propionic anhydride in dry pyridine at room temperature for 12 hr. The reaction mixture was poured onto ice to obtain a gummy product which was then dissolved in acetone and precipitated in cold water. The dissolution-precipitation was repeated three times. The hydrophobicized oc-CD is a white powder. 

Near the critical point, where the association constant Ka (determined by electrical conductivity) is large, the correction for ion-pairing is very important and the extrapolation to infinite dilution is quite sensitive to the magnitude of the association. Thus, for NaCl solutions at 670 K and 28 MPa (Ka 7000), the extrapolated value of (j)v is -16300 cm moT , while the value without ion-pairing is -8065 cm moT . 

T. Akashi, T. Maruyama, T. Goto, Transport of lanthanum ion and hole in LaCrOs determined by electrical conductivity measurements. Solid State Ionics 164,177-183 (2003)... 

Neves CMSS, Rodriguez AR, Kurina KA, Esperan9a JMSS, Freire MG, Coutinho JAP (2013) Solubility of non-aromatic hexafluorophosphate-based salts and ionic liquids in water determined by electrical conductivity. Fluid Phase Equilib 358 50-55... 

The interaction of cationic fluorocarbon and hydrocarbon surfactants was studied by Tamori et al. [145]. The mixed cmc of diethanolheptadecafluoro-2-2-undecanolammonium chloride and dodecyltrimethylammonium chloride was determined by electric conductivity measurements. Partition coefficients of alcohols (methanol and C4F7H2OH) and a fluorescent probe (pyrene-3-carboxaldehyde) between micelles and the bulk aqueous phase were determined. The data interpreted by a regular solution theory fitted an interaction parameter /3 = 1, indicating a much smaller repulsive interaction between the two cationic surfactants than that between an anionic fiuorinated surfactant and an anionic hydrocarbon-type surfactant. The weak repulsion between the two cationic surfactants was explained by a large difference in their cmc values. 

Total acidity and total chlorides can be deterrnined by conventional techniques after hydrolysing a sample. Satisfactory procedures for determining hydrogen chloride and free-sulfiir trioxide are described in the Hterature (18,41). Small amounts of both hydrogen chloride and sulfur trioxide can be found in the same sample because of the equiUbrium nature of the Hquid. Procedures for the direct deterrnination of pyrosulfuryl chloride have also been described (42,43), but are not generally required for routine analysis. Small concentrations of sulfuric acid can be deterrnined by electrical conductivity. 

Exhaustion The state in which the adsorbent is no longer capable of useful ion exchange the depletion of the exchanger s supply of available ions. The exhaustion point is determined arbitrarily in terms of (1) a value in parts per million of ions in the effluent solution and (2) the reduction in quality of the effluent water determined by a conductivity bridge which measures the resistance of the water to the flow of an electric current. 

The effect of water salinity on crop growth is largely of osmotic nature. Osmotic pressure is related to the total salt concentration rather than the concentration of individual ionic elements. Salinity is commonly expressed as the electric conductivity of the irrigation water. Salt concentration can be determined by Total Dissolved Solids (TDS) or by Electrical Conductivity (EC). Under a water scarcity condition, salt tolerance of agricultural crops will be the primordial parameter when the quality of irrigation water is implicated for the integrated water resources management [10]. 

It is not as easy as it appears to know whieh are the eleetrieally conducting species in molten salts. It seems to be nearly impossible to determine the electrically conducting species by experiment alone. ... 

Diffusion-Controlled Reactions. The specific rates of many of the reactions of elq exceed 10 Af-1 sec.-1, and it has been shown that many of these rates are diffusion controlled (92, 113). The parameters used in these calculations, which were carried out according to Debye s theory (41), were a diffusion coefficient of 10-4 sec.-1 (78, 113) and an effective radius of 2.5-3.0 A. (77). The energies of activation observed in e aq reactions are also of the order encountered in diffusion-controlled processes (121). A very recent experimental determination of the diffusion coefficient of e aq by electrical conductivity yielded the value 4.7 0.7 X 10 -5 cm.2 sec.-1 (65). This new value would imply a larger effective cross-section for e aq and would increase the number of diffusion-controlled reactions. A quantitative examination of the rate data for diffusion-controlled processes (47) compared with that of eaq reactions reveals however that most of the latter reactions with specific rates of < 1010 Af-1 sec.-1 are not diffusion controlled. 

Stainton [31] has described an automated method for the determination of sulphate and chloride in non saline waters. An ion exchange resin is used to convert the sulphates and chlorides to their free acids. Detection is achieved by electrical conductance. The use of silver-saturated cation exchange resin to precipitate chloride permits distinction between chloride and sulphate. High levels of nitrate, orthophosphate and fluoride give positive interference for sulphate bromide and iodide similarly interfere with chloride estimates. 

By the salinity of sea water is understood the number of grams of total salts in 1000 grams of the water. This may be determined gravimetrically or volumetrieally, the latter method being the most usual, the chlorine being determined, and from it the total salts calculated. This method of course implies suitable laboratory facilities, and if these arc not available the water must be stored until such time as it can be tested. To obviate this difficulty attempts have been made to determine salinity by electric conductivity measurements. By employing a standard sea water and comparing its conductivity with that of the unknown samples, it is claimed that very accurate results are easily obtained at sea or under conditions entire unsuitable for ordinary laboratory work.1... 

Corrosion and Ionisation.—Iron will remain untarnished for indefinite periods in the presence of concentrated solutions of the carbonates of the alkali metals, even in the presence of small quantities of other salts. If, however, the alkali carbonate is very dilute, it cannot entirely inhibit corrosion. Now, the minimum quantities of alkali carbonate required to inhibit the corrosive actions of a given concentration of various other salts of the same alkali metal have been determined.1 The results show that, if the added salts are arranged in order according to the amount of alkali carbonate required to inhibit corrosion, they are also not merely in the order of the relative strengths of their acid radicles, but the relative quantities of carbonate bear a general relationship to the numerical values found for the strengths of the acids by electrical conductivity methods. This is well illustrated in the following table —... 

The activity of a species is a measure of its effective concentration as determined by colligative properties (such as increasing the boiling point or decreasing the freezing point of water), by electrical conductivity, and by the mass action effect. 

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