Specific conductivity ionic

Specific conductance Ionic strength Surface tension (20°C)... 

Specific Conductance. The specific conductance depends on the total concentration of the dissolved ioni2ed substances, ie, the ionic strength of a water sample. It is an expression of the abiUty of the water to conduct an electric current. Freshly distilled water has a conductance of 0.5—2 ]lS/cm, whereas that of potable water generally is 50—1500 ]lS/cm. The conductivity of a water sample is measured by means of an a-c Wheatstone-bridge circuit with a null indicator and a conductance cell. Each cell has an associated constant which, when multiphed by the conductance, yields the specific conductance. 

The concentration of dissolved ionic substances can be roughly estimated by multiplying the specific conductance by an empirical factor of 0.55—0.9, depending on temperature and soluble components. Since specific conductance is temperature dependent, all samples should be measured at the same temperature. Alternatively, an appropriate temperature-correction factor obtained by comparisons with known concentrations of potassium chloride may be used. Instmments are available that automatically correct conductance measurements for different temperatures. 

NOTE The specific conductance factor varies considerably, depending on several factors, including the concentration of ionic species present in the water. In general, the factor decreases with increase in the concentration of ionic species. Thus, for city water a factor of 0.65 is a good approximation for BW in higher pressure WT boilers, a factor of0.575 is preferred by the author, and for BW in lower pressure FT boilers, a factor of 0.5 is preferred by the author. 

The room temperature specific conductivity of a number of ionic liquids is reported in Table 2, together with their viscosity. It can be seen from the table, that the conductivity varies in the range of 0.1-13 mS/cm. The most conductive IL in the series shown in the table is EMImBF4. 

A plot of the spectroscopically computed maximum ionic concentrations [SD ions]m (sum of free ions and ion-pairs) at the end of the reactions (m denotes maximum values throughout this paper, the subscript 0 denotes initial values) against the final values of the specific conductivity Km. for the equivalent runs (Tables 1 and 2) gave a straight line through the origin, showing that virtually only free ions were present in our systems if there had been important quantities of ion-pairs, this plot would have been markedly curved. 

These observations do not, however, mean that TBT carboxylates and TBTCl are ionic in nature. After detailed analysis of the physical evidence such as the low specific conductance and dipole moment of trialkyltin halides, Neumann has concluded that they have no "salt-like constitution" (6). Bonding in the trialkyltin carboxylates also is essentially similar to that in covalent alkyl esters, as evidenced by the low dipole moment of 2.2D for tributyltin acetate in benzene, as compared to 1.9D for alkyl acetates (7). 

The ionic conductivity of a solution depends on the viscosity, diffusivity, and dielectric constant of the solvent, and the dissociation constant of the molecule. EFL mixtures can carry charge. The conductivity of perfluoroacetate salts in EFL mixtures of carbon dioxide and methanol is large (10 to 10 " S/cm for salt concentrations of 0.05-5 mM) and increases with salt concentration. The ionic conductivity of tetra-methylammonium bicarbonate (TMAHCO3) in methanol/C02 mixtures has specific conductivities in the range of 9-14 mS/cm for pure methanol at pressures varying from 5.8 to 14.1 MPa, which decreases with added CO2 to a value of 1-2 mS/cm for 0.50 mole fraction CO2 for all pressures studied. When as much as 0.70 mole fraction... 

Ionic Transport, a. Conductivity The specific conductance of the SPS (Na+ form) membranes is shown in Fig. 8, whose data are summarized in Table II, including values of an apparent energy of activation. An exponential increase in ionic conductance together with a decrease in an apparent energy of activation may be related to a decrease in a "jump" distance between ion-exchange sites as a function of lEC. 

TR - transition region nearly pure (97-100%) ionic conductor mixed with second compound K - specific conductivity ohm cm D.C. - dielectric constant r - viscosity, centipoises ... 

In 1C, the election-detection mode is the one based on conductivity measurements of solutions in which the ionic load of the eluent is low, either due to the use of eluents of low specific conductivity, or due to the chemical suppression of the eluent conductivity achieved by proper devices (see further). Nevertheless, there are applications in which this kind of detection is not applicable, e.g., for species with low specific conductivity or for species (metals) that can precipitate during the classical detection with suppression. Among the techniques that can be used as an alternative to conductometric detection, spectrophotometry, amperometry, and spectroscopy (atomic absorption, AA, atomic emission, AE) or spectrometry (inductively coupled plasma-mass spectrometry, ICP-MS, and MS) are those most widely used. Hence, the wide number of techniques available, together with the improvement of stationary phase technology, makes it possible to widen the spectrum of substances analyzable by 1C and to achieve extremely low detection limits. 

Table 3.2-1 Specific conductivity data for non-haloaluminate alkylimidazolium-based ionic... 

Specific conductivity data for binary haloaluminate ionic liquids. 

Table 3.2-3 Specific conductivity data for other room-temperature ionic liquids... 

A large number of oxides which are commonly solid insulators at room temperature (e.g., A1203) yield highly conducting (specific conductance > 10 ohm-1 cm-1) melts on fusion. Some of these melts are undoubtedly ionic conductors whereas others are electronic conductors. It is, however, not always possible to differentiate between these two general types since both mechanisms may be operative to comparable extents at a particular temperature. Relatively few experiments have been reported in which reliable estimates of the transport numbers of either ions or electrons could be made. The subdivision in this section into the two general types of conductors is thus not to be interpreted as rigid. 

Fig. 1. Specific conductivity of V206 (semiconductor) and PbO (ionic conductor) (16).

Besides PbO which shows a large change in conductivity in the vicinity of the melting point (Fig. 1), liquid Li20 is probably an ionic melt. The specific conductivity of the solid near the melting temperature of 1570°C is about 105 ohm-1 cm-1 but that of the melt is 7 ohm-1 cm-1 (57). The latter value is comparable to that of molten LiCl, but the increase on fusion is even greater than the halides. By analogy, other molten alkali oxides are probably also ionic conductors. 

Na and K azides were detd in solns of varying concns by Petrikalns Ogrins (Ref 12).They also detd the density and refractive index for crystn Na and K azides. The ionic conductance of solid Li azide, as detd by Jacobs Tomkins (Ref 18), obeyed the general equation log k = log A - (E/2.303RT) where k is the specific conductivity in ohm-1 cm"1 A is a constant and E is activation energy in kcal/ mol. For Li azide log A 0.840, E is 19.1 and T, the temp range 300 370°K. The Raman Effect of crystn Li azide was detd by Kahovec Kohlrausch (Ref 14/, the observed frequency, 1368.7 cm-1, corresponded to the oscillation in a linear triatomic molecule. 

The Fuoss-Onsager-Skinner equation satisfactorily describes the electrolytic conductance of lithium bromide in acetone. Values of 198.1 0.9 Q l cm2 eq l and (3.3 0.1) X I03 are established for A0 and KA, respectively, at 25°C furthermore, a value of 2.53 A is obtained for the sum of the ionic radii ( ). When bromosuccinic acid is added to 10 5 N lithium bromide in acetone, there is a decrease in the specific conductance of lithium bromide rather than the increase that is observed at higher concentrations. As the concentration of bromosuccinic acid is increased, the values obtained for A0 and KA decrease, while those for a increase when the bromosuccinic acid and acetone are considered to constitute a mixed solvent. These results do not permit any simple explanation. When bromosuccinic acid and acetone are considered a mixed solvent, the Fuoss-Onsager-Skinner theory does not describe the system. 

Some remarks are necessary on the purity of chemicals. Ionic impurity causes a flow of electric current through polymerizing solution. This is certainly undesirable because it may give rise to a temperature rise and because it may trigger electrolytic reactions on the electrodes, which would screen the effect looked for. Thus, the solvents and monomers were most carefully purified. The impurity level was checked by the electric conductivity determined from the current and field intensities before polymerization. For example, 1,2-dichloroethane, the solvent most frequently used in our investigations, was purified until its specific conductivity was lowered below 1010 mho/cm. It should be mentioned... 

The specific conductivity of the solution, K (Q-cm)1, can be found in reference handbooks or estimated from limiting ionic conductances. 

Several electrolytic-conductivity detectors are produced (Table 3.5). The Laboratory Data Control Model 701 Conducto Monitor (Fig.3.59) may be operated in either a differential mode or an absolute mode. It provides direct readout in units of specific conductance and differences as small as 0.01% in the differential mode between the carrier and the carrier plus solute can be measured. The dynamic range of linearity is 0.01-100,000 pSl 1 /cm. The detector can function in solvents ranging from distilled water to concentrated salt solutions without the necessity of changing the cell. The volume of the cell is 2.5 pi, and the nominal cell constant is 20 cm-1. This type of detector is of use mainly in high-speed ion-exchange chromatography for the detection of ionic species. 

Specific conductance, or the conductivity of a solution, is attributed to the ionic species (cations and anions) present in the solution. The conductivity to IDS ratio should be between 1.4 and 1.8, i.e.,... 

Gallium(III) bromide is a hygroscopic, white solid which sublimes readily and melts at 122.5° to a covalent, dimeric liquid. The solid is ionic and its electrical conductivity at the melting point is twenty-three times that of the liquid.5 The vapor pressure of the liquid at T°K is given by the equation log p(mm.) = 8.554 — 3129/T and the heat of dissociation of the dimer in the gas phase is 18.5 kcal./mol.3 At 125° the liquid has the following properties 5,6 density, 3.1076 dynamic viscosity, 2.780 c.p. surface tension, 34.8 dynes/cm. and specific conductivity, 7.2 X 10-7 ohm-1 cm.-1 Gallium(III) bromide readily hydrolyzes in water and forms addition compounds with ligands such as ammonia, pyridine, and phosphorus oxychloride. 

Ionic liquid Density/gcm 3 Dynamic viscosity/mPa s Specific conductivity/mS cm-1 A Red-Ox/V... 

---