Mercury distribution coefficient

A further complication in the equilibrium is shown in Fig. 8.3-7, which shows the mercury distribution coefficient as a function of amine concentration for a fixed level of mercuiy. At low amine concentrations the distribution coefficient increases with amine level in the way that is expected for reaction (8.2-7) or (8.2-8), but above a certain amine level the distribution coefficient becomes constant. This behavior indicates that some separate phenomenon, such as limited solubility or association of the amine-hydrochloride salt, keeps its activity constant with increasing concentraticm. This is a common experimental observation in such systems. 

Voltaic cells 64. 504 Voltammetry 7, 591 anodic stripping, 621 concentration step, 621 mercury drop electrode, 623 mercury film electrode, 623 peak breadth, 622 peak current, 622 peak potential, 622 purity of reagents, 624 voltammogram, 622 D. of lead in tap water, 625 Volume distribution coefficient 196 Volume of 1 g of water at various temperatures, (T) 87... 

Fig. 8.39 Distribution coefficients (K and defining the sorption of inorganic Hg(II) to estuarine particles versus salinity (S, in g/L) in the Beaulieu, Mersey, and Plym estuaries. Reprinted with permission from Turner A, Millward GE, LeRoux SM (2001) Sediment-water partitioning of inorganic mercuries in estuaries. Environ Sci Technol 35 4648-4654. Copyright 2001 American Chemical Society...

Yan [38] further simplified the equations for batch extractions by assuming an irreversible, first-order extraction reaction between the solute and the carrier, irreversible first-order stripping reaction between the complex carrier and the internal reagent and constant distribution coefficients. Weiss et al. [39] proposed an empirical model for the extraction of mercury. Recently, Baneijea et al. [40] and Chakraborty et al. [4] presented an unsteady-state mathematical models to explain type 2 facilitation. 

Solvent extraction of the slightly ionized mercury (II) azide complex, HgNs, or neutral Hg(N3)2 in the pH range 4-6 has been investigated. With n-butanol the distribution coefficient is 10.6 at 25°C. The complex obeys Beer s law at 248 nm in both aqueous and butanol solution [23]. 

Calcium(II), which shows no appreciable complexing, has a distribution coefficient of 147 in 0.5 M perchloric acid and 191 in 0.5 M hydrochloric acid. Strelow. Rethc-meyer, and Bothnia [10] also reported data for nitric and sulfuric acids that showed complexation in some cases. Mercury(II), bismuth(III), cadmium(II), zinc(II), and lead(II) form bromide complexes and are eluted in the order given in 0.1 to 0.6 M hydrobromic acid [11]. Most other metal cations remain on the column. Aluminu-m(III), molybdenum(VI), niobium(V), tin(IV), tantalum(V), uranium(VI), tung-sten(VI), and zirconium(IV) form anionic fluoride complexes and are quickly eluted from a hydrogen-form cation-exchange column with 0.1 to 0.2 M HF [12]. 

FIGURE 8.3-6 Distribution coefficient of mercuric ion from 4.63 M NaCI solution at 22 C and pH 1 as a function of organic-phase mercury concentration. The organic phase is TIOA in xylene at 0.1 AT and O.S M as indicated. From Ref. 13, with permission. 

Water is flowing through a 150 mm diameter pipe and its flowrate is measured by means of a 50 mm diameter orifice, across which the pressure differential is 2.27 x 104 N/m2. The coefficient of discharge of the orifice meter is independently checked by means of a pitot tube which, when situated at the axis of the pipe, gave a reading of 100 mm on a mercury-under-water manometer. On the assumption that the flow in the pipe is turbulent and that the velocity distribution over the cross-section is given by the Prandtl one-seventh power law, calculate the coefficient of discharge of the orifice meter. 

We found the latter factor-voids to be important. Experimental results showed that when green coke was calcined under the new methods, and the derived calcined coke was observed by scanning electron microscopy (Figure 2) and its pore size distribution was measured by mercury porosimetry (Figure 3), microcracks of significant sizes (1 to 60 microns) were developed. This was an important contribution to the reduction of the thermal expansion coefficients of the calcined coke processed under the new method. 

A cold-trap pre-concentration procedure, which is incorporated into a standard jlameless atomic absorption analysis of mercury in environmental samples, has been used for both shipboard and laboratory analyses of mercury in seawater, The coefficient of variation for seawater containing 25 ng Hg/l, is 15%, and a detection limit of approximately 0,2 ng Hg is attainable. In surface seawaters of coastal and open regions of the northwest Atlantic Ocean mercury concentrations appear to decrease with increasing distance from terrestrial sources. In the open ocean samples they are less than 10 ng/l. and rather uniformly distributed. The amounts of mercury in inshore samples can approach 50 ng/l, A significant mercury fraction characterized by a stable association with organic material may be present in coastal waters. 

Currently no adequate quantitative theory of the discrete-ion potentials for adsorbed counterions at ionized monolayers exists although work on this problem is in progress. These potentials are more difficult to determine than those for the mercury/electrolyte interface because the non-aqueous phase is a dielectric medium and the distribution of counterions in the monolayer region is more complicated. However the physical nature of discrete-ion potentials for the adsorbed counterions can be described qualitatively. This paper investigates the experimental evidence for the discrete-ion effect at ionized monolayers by testing our model on the results of Mingins and Pethica (9, 10) for SODS. The simultaneous use of the Esin-Markov coefficient (Equation 3) and the surface potential AV as functions of A at the same electrolyte concentration c yields the specific adsorption potentials for both types of adsorbed Na+ ions—bound and mobile. Two parameters which need to be chosen are the density of sites available to the adsorbed mobile Na+ ions and the capacity per unit area of the monolayer region. The present work illustrates the value... 

The low concentration of protein in the interstitial fluid has been suggested as another factor which may reduce the distribution of some substances in the central nervous system. Lipid soluble compounds, such as methyl mercury which is toxic to the central nervous system (see Chapter 7). can enter the brain readily, the facility being reflected by the partition coefficient. Another example which illustrates the importance of the lipophilicity in the tissue distribution and duration of action of a foreign compound is afforded by a comparison of the drugs thiopental and pentobarbital (figure 3,5). These drugs are very similar in structure, only differing by one atom. Their pKa values are similar and consequently the... 

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