Specific electrical resistivity water, concentration

The salinity may be determined directly as a total content of water-soluble salts, or as a sum of contents of particular ions. The measurement of the specific electric resistance of the soil is a very rough, but simple and rapid method. It is used for soil surveys on a wide scale. For achieving more precise results, it is possible to use a method standardized by measuring the resistance in saturated soil paste (the soil paste is prepared by mixing a soil sample with distilled water to obtain a moderately liquefied paste) and the results are corrected with respect to a temperature of 16°C. Tables are used to convert the measured electrical resistance values to the soil concentration. For more precise data, it is possible to separate the solution from the saturated soil paste and to measure the specific electric conductivity. The solution separated from the soil paste is called the saturated soil extract. 

Let us consider a particular example of the effect of RS substances on the water resistance of adhesive-bonded joints. Adhesives based on imsaturated polyester resins, such as PN-1, are distinguished by low water resistance. The influence of water on a steel joint cemented by such an adhesive actually results in some initial increase of the specific electrical resistance along the adhesive-steel interface and then in an abrupt drop (Fig. 5.5). The increase is explained by more complete consumption of the monomer in the system. When ATG is added to the adhesive (which decreases the interphase tension) the specific electrical resistance stabilizes after a drop. The decrease seems to be related to the processes of relaxation of the internal stresses in the adhesive interlayer. The stresses facilitate the diffusion of liquids in polymeric materials, in particular the stress concentration at the polymer-metal interface. 

Grayish-white cubic crystals lustrous and brittle density 5.323 g/cm hardness 6.0 Mohs melts at 938.2°C vaporizes at 2,833°C a poor conductor of electricity electrical resistivity 47 microhm-cm dielectric constant 15.7 specific magnetic susceptibility (at 20°C) 0.122x10 insoluble in water, dilute acids and dilute alkalies attacked by concentrated nitric and sulfuric acids, aqua regia and fused alkalies. 

The effective solute (ts) transport number, ranged from 93% to 98%, even if reduced to 88% for sodium lactate. The water transport number (tw) increased from 9.3 to 15.6 and correspondently the maximum salt weight concentration in the concentrated stream (CBc,max) ranged from 286 to 350 kg/m3. Finally, while the surface resistance (rc) of the cation-exchange membranes was found to be about constant (5 2fl cm2), ra tended to increase with A/b. However, the specific electric energy consumption (e) slightly increased from 0.19 to 0.22 kWh/kg of salt recovered. 

Effect of the salt molecular mass (MB) on the cation transport number (C) in the corresponding solution effective solute (tB) and water (%) transport numbers surface resistances (rc, ra) of, and counterion transport numbers (tc+, ta ) in cation- and anion-exchange membranes specific electric energy consumption (e) in the case of 90% salt recovery at 1 A, and maximum solute concentration theoretically achievable in the concentrating stream (CBCmax). Note NaCl, sodium chloride Na-A, acetate Na-P, propionate Na-L, lactate. 

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