Equivalent concentration

Parenthetical value is an approximately equivalent concentration, not to be exceeded more than once per year. 

Analytical Methods. Most analytical methods use the oxidizing power of iodine for its deterrnination. The results are generaHy expressed as an equivalent concentration of elemental iodine. The choice of a method for the analysis of iodine depends on the concentration range to be deterrnined. 

The total concentration or amount of chlorine-based oxidants is often expressed as available chorine or less frequendy as active chlorine. Available chlorine is the equivalent concentration or amount of Cl needed to make the oxidant according to equations 1—4. Active chlorine is the equivalent concentration or amount of Cl atoms that can accept two electrons. This is a convention, not a description of the reaction mechanism of the oxidant. Because Cl only accepts two electrons as does HOCl and monochloramines, it only has one active Cl atom according to the definition. Thus the active chlorine is always one-half of the available chlorine. The available chlorine is usually measured by iodomettic titration (7,8). The weight of available chlorine can also be calculated by equation 5. 

Upon strong chelation, aU. four protons are displaced and base titration resembles that of a typical strong acid at four times the equivalent concentration. This statement is in agreement with equation 19, which shows that pM can be large (low concentration of free metal) at low pH if iC is large (strong chelation). 

Available Chlorine Test. The chlorine germicidal equivalent concentration test is a practical-type test. It is called a capacity test. Under practical conditions of use, a container of disinfectant might receive many soiled, contaminated instniments or other items to be disinfected. Eventually, the capacity of the disinfectant to serve its function would be overloaded due to reaction with the accumulated organic matter and organisms. The chlorine germicidal equivalent concentration test compares the load of a culture of bacteria that a concentration of a disinfectant will absorb and still kill bacteria, as compared to standard concentrations of sodium hypochlorite tested similarly. In the test, 10 successive additions of the test culture are added to each of 3 concentrations of the hypochlorite. One min after each addition a sample is transferred to the subculture medium and the next addition is made 1.5 min after the previous one. The disinfectant is then evaluated in a manner similar to the phenol coefficient test. For equivalence, the disinfectant must yield the same number of negative tubes as one of the chlorine standards. 

This equation has the same form of that obtained for solid diffusion control with D,j replaced by the equivalent concentration-dependent diffusivity = pDpj/[ pn]Ki l - /i,//i)) ]. Numerical results for the case of adsorption on an initially clean particle are given in Fig. 16-18 for different values of A = = 1 - R. The upt e curves become... 

It is now useful to recall the concepts of molarity and fractional saturation (Astarita etal., 1983). The molarity, mj, of areactive MSA is the total equivalent concentration of species that may react with component A. On the other hand, the fractional saturation, uj, is a variable that represents the degree of saturation of chemically combined A in the jth lean phase. Therefore, ujmj is the total concentration of chemically combined A in the yth MSA. Hence, the total concentration of A in MSA j can be expressed as... 

The decrease in rate was proportional to the concentration of dioxane in the reaction mixture. An equivalent concentration of p-xylene (whose dielectric constant is similar to that of dioxane) produced a smaller decrease, consistent with simple dilution of the reactants. It was, therefore, hypothesized that dioxane forms an H-bonded molecular complex with phenol, the complexed form of the phenol being unreactive. The data could be accounted for with a 2 1 stoichiometry (phe-nokdioxane). This argument was supported by experiments with tetrahydrofuran, which also decreased the rate, but which required a 1 1 stoichiometry to describe the rate data. 

Further support for this pathway was provided by competition feeding studies. If 104 were not a true biosynthetic intermediate and were incorporated due to some flexibility in the biosynthetic enzymes, then its incorporation would be expected to be reduced by an equivalent concentration of the true substrate 102 or 103. If it were a real intermediate, then it would be expected that incorporation of earlier intermediates would be reduced by an equivalent concentration of 104. Precursor 104, labeled with deuterium at the O-methyl group, was co-fed with an approximately equal concentration of either 102 or 103 labeled with deuterium at the C-5 methyl group, and relative incorporation levels were compared by measurement of the CD3 peak intensities in the 2H NMR spectrum of the labeled azinomycin B. In each case, there was approximately twice as much deuterium labeling at the O-methyl group as at the other methyl group, consistently with 104 being a true biosynthetic intermediate. 

The addition of the neutral salt (the second set of experiments) accelerates the reaction rate far more than does an equivalent concentration of excess amine. In the absence of the salt, a fifteen-fold increase in the initial amine concentration (from 0.1 M to 1.5 M) raises the measured rate coefficient by a factor of four, but at a salt concentration of 0.34 M the measured second-order rate coefficient is nine times larger than with the salt absent. 

Consider an experiment with equivalent concentrations, [PuVI]o = 2[UIV]o. The experimental data are given in Table 2-5. The fit according to Eq. (2-42) is shown in... 

If an inhalation study in animals, list conversion factors used in determining human equivalent concentration NA... 

Whyte, J.J., Van den Heuvel, M.R.M., and Clemons, J.H.M. et al. (1998). Mammalian and teleost cell line bioassays and chemically derived 2,3,7,8-TCDD equivalent concentrations in lake trout from Lake Superior and Lake Ontario, North America. Environmental Toxicology and Chemistry 17, 2214-2226. 

The value of k will be half that ordinarily obtained when molar rather than equivalent concentrations are used. Rate constants will be expressed universally according to the convention stated above. 

In integral analysis concentration-versus-time (or equivalently concentration-versus-distance from the inlet of the integral flow reactor) data are known. Kinetic expressions to be determined are incorporated into the differential material balance equations ... 

Salinities of inclusion fluids from epithermal vein-type deposits clearly indicate that the salinities of inclusion fluids from these types of deposits are distinctly different, that is, 20-2 NaCl equivalent wt% (base-metal vein-type deposits) and 0-3 wt% (Au-Ag vein-type deposits) (Shikazono, 1985b) (Table 1.13). Salinities of inclusion fluids from Kuroko deposits (0.5-5 wt% NaCl equivalent concentration) are between these two types of deposits. This kind of difference is observed in epithermal deposits in other countries (Hedenquist and Henley, 1985). 

Salinity (NaCl equivalent concentration) of inclusion fluids is 1-6 wt%, 1-14.5 wt% and 0-3 wt% for Kuroko deposits, base metal vein-type deposits, and Au-Ag vein-type deposits, respectively. These data clearly demonstrate that the salinity of inclusion fluids for the base metal-rich deposits (base metal vein-type deposits, Kuroko deposits) is higher than that of the Au-Ag vein-type deposits, while homogenization temperatures of fluid inclusion for these three types of ore deposits do not show a wide... 

Oxidant (Equivalent Concentrations) % Bromate After 60 Days Storage... 

Cortes et al. [634] have recently used /rSEC-GC/LC in a comparative quantitative study of dissolution and dissolution/precipitation of PC/(2,4-di-f-butylphenol, nonylphenol isomers, Tinuvin 329, Irgafos 168) and ABS/(nonylphenol isomers, Tinuvin P, BBP, Vanox 2246, Tinuvin 328/770, Topanol CA, Acrawax). For the ABS sample the dissolution approach determined a four-fold higher concentration for Vanox 2246 than by dissolution/precipitation of the sample, indicating that precipitation can yield low (incorrect) results for additives which exhibit solubility dependence. Using both sample preparations equivalent concentrations were observed for the additives of the PC sample, except for Tinuvin 329. 

Noise levels will be different for different models of the same type of detector, and for a given model will depend very much on how the detector is used. The noise equivalent concentration refers to a solute with favourable properties, and may be very much higher for other solutes. 

Fluorescence detectors can be made much more sensitive than uv absorbance detectors for favourable solutes (such as anthracene) the noise equivalent concentration can be as low as 10 12 g cm-3. Because both the excitation wavelength and the detected wavelength can be varied, the detector can be made highly selective, which can be very useful in trace analysis. The response of the detector is linear provided that no more than about 10% of the incident radiation is absorbed by the sample. This results in a linear range of 103-104. 

One type of ec detector (the coulometric detector) reacts all of the electroactive solute passing through it. This type has never become very popular (there is only one on the market at the moment). Another type (the amperometric detector) reacts a much smaller quantity of the solute, less than 1%. The currents observed with these detectors are very small (nanoamps), but such currents are not too difficult to measure and the detector has a high sensitivity, considerably higher than that of uv/visible absorbance detectors although not as good as fluorescence detectors. Noise equivalent concentrations of about 10, 0g cm-3 have been obtained in favourable cases. Another advantage of these detectors is that they can be made with a very small internal volume. 

Refractive index detectors are not as sensitive as uv absorbance detectors. The best noise levels obtainable are about 1CT7 riu (refractive index units), which corresponds to a noise equivalent concentration of about 10-6 g cmT3 for most solutes. The linear range of most ri detectors is about 104. If you want to operate them at their highest sensitivity you have to have very good control of the temperature of the instrument and of the composition of the mobile phase. Because of their sensitivity to mobile phase composition it is very difficult to do gradient elution work, and they are generally held to be unsuitable for this purpose. 

Some commercially available detectors have a number of detection modes built into a single unit. Fig. 2.4o is a diagram of the detector used in the Perkin Elmer 3D system, which combines uv absorption, fluorescence and conductivity detection. The uv function is a fixed wavelength (254 nm) detector, and the fluorescence function can monitor emission above 280 nm, based on excitation at 254 nm. The metal inlet and outlet tubes act as the electrodes in the conductance cell. The detection modes can be operated independently or simultaneously, using a multichannel recorder. In the conductivity mode, using NaCl, a linear range of 103 and a noise equivalent concentration of 5 x 10 8 g cm-3 have been obtained. 

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