Conductance ratio

Figure 2-5. Thermal conductivity ratio for gases. (From Gas Processors Suppliers Association, Engineering Data Book, 10th Edition.)...

Figure 1 The solubility of the principal atmospheric gases in seawater, as a function of temperature. Units are millilitres of gas contained in a litre of seawater of salinity 35 psu, assuming an overlying atmosphere purely of each gas. Note that salinity is defined in terms of a conductivity ratio of seawater to a standard KC1 solution and so is dimensionless. The term practical salinity unit , or psu, is often used to define salinity values, however. It is numerically practically identical to the old style unit of parts per thousand by weight...

Fig. 4.4 (a) Comparison on a logarithmic scale of the conductivity ratio and the thermodynamic activity ratio of alkali oxide in several silica based glasses. Activity ratios are deduced from potentiometric measurements, (b) On the same scale, conductivity vs activity of AgX (X = Cl, Br, I) in phosphate glasses. Activity values are deduced from calorimetric measurements. 

Table 3.3 Equation Relating the Conductivity Ratio Measured by an Inductive Salinity to Practical Salinity, PSS 1978.

The PSS-78 is based on the measurement of a conductivity ratio and, hence, is technically unitless. Nevertheless, some oceanographers use a psu designation to represent a practical salinity unit and others report salinity in units of parts per thousand (%o). The latter convention has been adopted in this text. In any event, it is important to appreciate that the practical salinity is no longer directly traceable to the theoretical definition given in Eq. 3.1. 

Conductance measurements of biguanide and its nitrate at various concentrations 672) have given values for their conductance ratio of the... 

A closer agreement is scarcely to be expected since no correction has been made for the concentration potential h and the conductivity ratio of the two solutions is only an approximate measure of the chlorine ion concentrations, which in turn are not identical with their activities. 

The effect of flow depends solely on a Peclet number formed using the conductance in a stagnant medium, k A/Q), as the characteristic length. Equation (4-60) has wider generality it is valid for a fluid or solid particle of any shape at any Re so long as Pe 0 and the stream far from the particle is uniform. This expression gives a good prediction of the conductance ratio for k/k < 1.2. Equation (3-45) is the special case of Eq. (4-60) for spheres. The next term in the series expansion depends explicitly upon the shape and the orientation of the particle. 

Fig. 1.2. Plots of the potential drop across the packed and the open segment of a CEC column against the dimensionless packed length, X, with conductivity ratio, aoperXvpacked, as the parameter. The respective currents with columns having packed segments of 0, 10 and 20 cm were reported as 6.6, 3.9 and 2.6 p.A, respectively. The conditions were fused silica capillary, 50 pm x 30 cm applied voltage, 18 kV column packing, 3.5 mm Zorbax ODS, 80 A mobile phase, 50 % (v/v) ACN in 10 mM sodium borate, pH 8.0.

Fig. 1.3. Plots of the ratio of the equivalent and the actual lengths of the packed segment, Le/Lpacked, against X with conductivity ratio as the parameter. Conditions same as in Figure 1.2.

Fig. 1.9. Plot of the pressure difference, Pj-Po, across the packed segment against X with the conductivity ratio as the parameter. At the top is a schematic illustration of the pressure gradients across the open and the packed segments of the column when ffopen/crpacked = 3.1. Conditions used are Apacked/Aopen = 0.4 ep = 0.4 r = 10"3 N m"2 s 1, peo,packed = peo.open =3.33 x 10 m2V" s. Rest of the conditions same as in Figure 1.2.

The pressure difference, Pi - Po, as calculated from Eq. 1.43 is plotted as a function of the dimensionless packed length, X, with the conductivity ratio as the parameter in Figure 1.9. The pressure drop across any of the segments, Pi - Po, is maximum at small X values and becomes zero at the extremity X = 1. In the present... 

In 1978, the Joint Panel for Oceanographic Tables and Standards (JPOTS) decided that a new definition was needed for salinity that was based more on a salinity/conductivity ratio. 

This new relationship was termed the practical salinity scale and is based on a background paper by Lewis (1978). The practical salinity of a water sample is defined in terms of the conductivity ratio, F15, which is defined as follows ... 

Therefore, a standard seawater sample with a salinity (5) of 35 (with no %o units needed) has a conductivity ratio of 1 at 15°C and 1 atmosphere, using a standard KC1 solution of 32.4356 g in a 1 kg mass of solution. Finally, recent applications of microwave remote sensing have been used to determine surface water of gradients of salinity in coastal regions, particularly in river plume regions (Goodberlet et al., 1997). 

Salinity was first rigorously defined by Knudsen (1902, p. 28) as the weight in grams of the dissolved inorganic matter in one kilogram of seawater after all bromide and iodide have been replaced by the equivalent amount of chloride and all carbonate converted to oxide. In 1978, the JPOTS decided that a new definition was needed for salinity that was based more on a salinity/conductivity ratio and was termed the practical salinity scale. 

For gas or ions, FET sensors response speed is not the main prerequisite because of the relatively long time constants associated with chemical measurements. However, the ON-OFF conductance ratio, as well as the transconductance IJ Vg should be maximized. As far as noise is concerned, attention shold be paid to reducing both the noise-equivalent input current zn and voltage vn generators of the sensor. In fact, the total rms input noise for unity bandwidth of such a device can be expressed in a first approximation as (Motchenbacher and Fitchen, 1973)... 

Electrical conductivity measurements in porous media have long been used for evaluation of porosity and permeability of various geological samples [33-36]. In CEC, it is important to characterize the column permeability in the appropriate manner. One way to characterize the permeability in CEC of the column packing is by the conductivity ratio, < >, which is defined as [36,37]... 

For the estimation of ( ), empirical relationships can be used. These include the Tobias equation [38], in which the conductivity ratio is related to the porosity by the relationship... 

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