Concentration units, table

As the main aim of trace analysis is usually determination of the mass (expressed as the number of moles) of a given component in a studied sample, molar concentration is generally not used. Some exceptions are electrochemical methods, where the analytical signal (e.g., current intensity) is a direct function of molar concentration [9]. Therefore, in voltamperometric techniques the detection limits are usually given in molar concentration units (Table 1.2). Thus, for nickel (molar mass M = 58.7 g/mol) the detection limit in inverse voltammetry is approximately 6 X 10 mol/L, and is expressed as a mass fraction, 3.5 x 10 g/dm, or as a percentage, 0.35 x 10 %. In spectrophotometry, when concentrations are given in molar units then molar absorptivities are also used. For example, molar absorptivity e = 5xl0 " L/mol cm corresponds (for molar mass M = 58.7 g/mol) to molar absorptivity a = 5 x 10 /(58.7 x 10 )mL/g cm (i.e., 0.85 mL/g cm). 

In the polymer literature each of the five quantities listed above is encountered frequently. Complicating things still further is the fact that a variety of concentration units are used in actual practice. In addition, lUPAC terminology is different from the common names listed above. By way of summary, Table 9.1 lists the common and lUPAC names for these quantities and their definitions. Note that when

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Concentration units were given in microgram/liter of water and in microgram/ kilogram of SE/soil. The sampling network for SW and SE coincided geographically, and the same for GW and soil (see Fig. 6 for sample location and Table 2 for sample identification). 

The value of Kw is 1.04 x 10-14 at 298 K when expressed in concentration units of mol dm-3. Like all equilibrium constants, its value depends on the temperature. Table 6.2 lists a few values of Kw as a function of temperature. Note how Kw increases slightly as the temperature increases. 

There is tolerable agreement between the values in Tables XVI and XVH, in such cases as direct or almost direct comparison is possible. Thus, for example, the Russian value of 48.52% by weight for the solubility of neodymium chloride at 30°C may be compared with 49.7% by Hinchey and Cobble, at 25°C. Indeed, if one follows the solubilities reported for neodymium chloride back to Matignon, the values at or near 25°C are all reasonably close together (178, 201, 205, 207, 258, 259). On the question of comparability, it may be remarked here that solubility comparisons are from time to time precluded by the preference of some authors for weight units, and of others for volume concentration units. When densities are also given, then of course interconversion is straightforward, but densities are by no means always available when needed. 

Assumed source concentrations C0 for four arbitrary elements (column 2), mineral 1-liquid and mineral 2-liquid partition coefficients (columns 3 and 4), residual solid-liquid bulk partition coefficients calculated from mineral abundances listed in Table 9.2. Concentration units are arbitrary. 

The values for stability (formation) constants given in the Tables should be approached with some degree of caution, especially as they have been obtained at a variety of ionic strengths. Where two or more values have been reported we have sometimes quoted a mean value, sometimes the most recent, depending on circumstances. All data refer to aqueous solution, at 298.2 K, unless stated otherwise all are based on concentration units of mol dm all log K or log P values are logio. 

Table 5.1 Common Aqueous Concentration Units (where SW = seawater).

Solubility concentratiorrs can be expressed many ways, including molarity (mol/L), molality (mol/kg), mole fraction, weight percent, mass per unit volume (e g., g/L), etc. The conversion formttlas for solutiotts having different concentration units are presented in Table 1. 

Table 1. Conversion Formulas for Various Concentration Units... 

Concentrations of solutions can be expressed in units other than mol 1. For example, the concentration of medicines is often given in mg/ml. The table below gives information about some other common concentration units. 

When the units are mgl mL" (i.e. in clinically-relevant conditions), it appears that all BPA tested do not interfere with the complement system in the tested concentration range (Table 6). As regards the effects of NS-CA on this model, data from the literature are rather conflicting [5,32]. 

There are some abbreviations for concentration units that are often seen in the literature and will be used periodically in this text. These are listed in Table 1.3. Also listed is a common conversion to water or to air. 

Of the many alternative methods of handling such data the most satisfactory systematic procedure seems to be that developed by Kreuzer [ 1 i]. Assuming only that the Law of Mass Action applies in terms of concentration units to the individual steps of the association process, Kreuzer deduced practically valuable relations between the monomer concentrations and the mean degree of association. When the experimental precision justifies it, it is advisable to use the mole traction as concentration unit throughout such studies. Mecke has systematized the thermodynamic relations for association processes in solution [12] Some of Davies and Thomas s results obtained by the Kreuzer analysis of thermistor data are given in Table 3. AH12,... 

LAS. The toxicity of C12LAS to aquatic organisms has been widely studied and is reported to span a wide concentration range (Table II see ref. 65 for a more extensive review the references we report in this chapter were selected for applicability to the United States and Europe and for data quality). The toxicity mechanism of LAS and other surfactants (AS and AES) is unknown but is suspected to be polar narcosis. Acute toxicity to invertebrate species (48-h hC ) range from 1.7 mg/L for the oligochaete, Dero,... 

Various concentration units are used in chemistry, depending on the application (Table G.2). The most common is molarity. The molar concentration (molarity) of a solute in a solution is the number of moles of solute molecules or formula units divided by the volume of the solution (in liters). 

Table G2 Concentration Units Measure Units Note...

The data obtained in these equilibrium studies have been treated quantitatively by Carmichael and Heffel (53) and by Brown and Slusarczuk (33), who evaluated the equilibrium data in terms of cyclization constants. The latter are identical with ring-chain constants of the type of Eq. (29) where the concentrations are expressed in mole fractions of building units. Table XI... 

Table II. Composition of Reference and Model Ground Waters (All Concentration Units in ppm)...

Even though in many analytical applications presented in this table, the correlation coefficient r has acceptable values (above 0.995) for the quadratic and cubic calibration curves, a spectrometric instrument, which is calibrated in concentration units, usually uses a linear curve which is established using several spectrometric RMs which are effectively introduced into the calibration process. 

The following table provides guidance in the use of base 10 concentration units (presented in three preceding tables), since there are differences in colloquial usage worldwide. 

Table III. Accumulation of Pesticide Residue in Soil for Annual Addition Rate of One Concentration Unit and a Loss of One Half in the First Year...

In Table IV, equilibrium accumulated residues are presented for a larger range of constants and are compared with values obtained for comparable first-order kinetics. For these cases, the slow approach to limiting values can tax even the computer, and the values were therefore calculated by numerical approximation to that value of C for which the decrease in 1 year was just 1 concentration unit—i.e., the addition rate. 

Table IV. Limiting Maximum Accumulated Residues in Soil as Calculated for Michaelis-Menton Kinetics and a Single Annual Addition of One Concentration Unit...

The solvent term [H20] varies by a negligible amount in such reactions and is incorporated in the constants Kt and Kh. If the concentrations are expressed in mol dm Kt and Kh have the same units. Table 3.3 lists pKt values for some typical compounds. The behaviour of the conjugate base may be represented in line with equation(3.15). 

Note This table is based on the adoption of moles/liter for concentration units. More explicitly, the units should include the species involved. Thus for the reaction H2 -f- I2 —> 2III, which is experimentally first-order with respect to H2 and first-order with respect to I2, the proper units of A m are... 

The valne of R depends upon the unit used for the other variables. Table 11.1 gives its various values and units, along with the units used for AH and T. By convention, the concentration units used in the calculation of K are in gmmols/L. 

Equation [6.3] can be used for SI units (molm ), molarity (molL ) or molality (molkg ). In all cases, y is a dimensionless term, since a and [C] are expressed in the same units. The activity coefficient of a solute is effectively unity in dilute solution, decreasing as the solute concentration increases (Table 6.1). At high concentrations of certain ionic solutes, y may increase to become greater than unity. 

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