Partition coefficients chemical potentials

This is our principal result for the rate of desorption from an adsorbate that remains in quasi-equihbrium throughout desorption. Noteworthy is the clear separation into a dynamic factor, the sticking coefficient S 6, T), and a thermodynamic factor involving single-particle partition functions and the chemical potential of the adsorbate. The sticking coefficient is a measure of the efficiency of energy transfer in adsorption. Since energy supply from the... 

Neely WB, Branson DR, Blau GE. 1974. Partition coefficients to measure bioconcentration potential of organic chemicals in fish. Environmental Science and Technology 8 1113-1115. 

KoC is an important parameter which describes the potential for movement or mobility of pesticides in soil, sediment and groundwater. Because of the structural complexity of these agrochemical molecules, the above simple relationship which considers only the chemical s hydrophobicity may fail for polar and ionic compounds. The effects of pH, soil properties, mineral surfaces and other factors influencing sorption become important. Other quantities, KD (sorption partition coefficient to the whole soil on a dry weight basis) and KqM (organic matter-water partition coefficient) are also commonly used to describe the extent of sorption. K0M is often estimated as 0.56 KoC, implying that organic matter is 56% carbon. 

Laskowski [1] has thoroughly reviewed the physico-chemical properties of the SPs, and these are summarized briefly below. SPs are typically of low water solubility (in the low microgram per liter range) and are highly nonpolar (logarithmic octanol water partition coefficients of around 6-7), indicating potential for bioaccumulation. Fish bioconcentration factors (BCF) of several hundred to several thousand are reported however metabolism limits the amount of bioaccumulation,... 

The second boundary condition arises from the continuity of chemical potential [44], which implies - under ideally dilute conditions - a fixed ratio, the so-called (Nernst) distribution or partition coefficient, A n, between the concentrations at the adjacent positions of both media ... 

The correlation (or lack of correlation) of other physiochemical characteristics has not yet been established. For instance, are all surfactants irritants Can one classify severity by the size of the molecule Can octanol water partition coefficients predict irritation potential does a propensity to partition out of the ocular fluid mean that a compound presents more of an irritation hazard than one which is more water soluble Theoretically, these data should reflect the ability of a compound to penetrate the eye and cause an irreversible lesion. However, until definitive data are available, physical and chemical parameters will probably have limited utility in an overall assessment of irritation. 

Molecular connectivity indices are desirable as potential explanatory variables because they can be calculated for a nominal cost (fractions of a second by computer) and they describe fundamental relationships about chemical structure. That Is, they describe how non-hydrogen atoms of a molecule are "connected". Here we are most concerned with the statistical properties of molecular connectivity Indices for a large set of chemicals In TSCA and the presentation of the results of multivariate analyses using these Indices as explanatory variables to understand several properties important to environmental chemists. We will focus on two properties for which we have a relatively large data base (1) biodegradation as measured by the percentage of theoretical 5-day biochemical oxygen demand (B0D)( 11), and (2) n-octanol/water partition coefficient or hereafter termed log P (12). 

Freshwater mammals such as heaver may leave odors on the surface of their ponds and olfactorily sample the water or layer of air immediately above it. Lipids on water may form micelles, small blobs of molecules (from Latin mica, a grain, crumb, morsel) that enhance evaporation into the air layer by increased chemical potential. Some seahirds hunt hy odor (e.g. Hutchison and Wenzel, 1980 Nevitt, 1999). They may respond to prey volatiles (from krill, squid, or fish) that rise to the water surface and evaporate into the air. The air-water equilibrium for dilute solutions can be expressed by using partition coefficients, relative volatility, or Henry s law (Thibodeaux, 1979). 

The potential for 2,3-benzofuran to be bioconcentrated by aquatic organisms is likely to be moderate. A bioconcentration factor (BCE) is the ratio of the concentration of a chemical in the tissues of aquatic animals to the concentration of the chemical in the water in which they live. No experimentally measured value for the BCF of 2,3-benzofuran was located, but the octanol-water partition coefficient (K ) of 2,3-benzofuran has been measured as 468 (Leo et al. 1971). The empirical regressions of Neeley et al. (1974) relate the values of and BCF for other compounds, and can be used to estimate that the BCF of 2,3-benzofuran is approximately 40. If this estimate is correct, substantial bioconcentration of 2,3-benzofuran by aquatic organisms would not be expected. 

The partition coefficient Kq of an organic compound in the 1-octanol/water system is used to assess the bioaccumulation potential and the distribution pattern of drugs and pollutants. The partition coefficient of imidazole and ILs strongly depends on the hydrogen bond formed by these molecules and is less than one due to the high solubility in water. The low value of the 1-octanol/water partition coefficient is required for new substances, solvents, insecticides to avoid bioaccumulation. Kqw is an extremely important quantity because it is the basis of correlations to calculate bioaccumulation, toxicity, and sorption to soils and sediments. Computing the activity of a chemical in human, fish, or animal lipid, which is where pollutants that are hydrophobic will appear, is a difficult task. Thus, it is simpler to measure the 1-octanol/water partition coefficient. This parameter is used as the primary parameter characterizing hydrophobisity. 

From Fig. 19.3a-c, and as opposed to purely sorption controlled processes, it can be seen that during pervaporation both sorption and diffusion control the process performance because the membrane is a transport barrier. As a consequence, the flux 7i of solute i across the membrane is expressed as the product of both the sorption (partition) coefficient S, and the membrane diffusion coefficient Di, the so-called membrane permeability U, divided by the membrane thickness f and times the driving force, which maybe expressed as a gradient of partial pressures in place of chemical potentials [6] ... 

Sagar, P.M., Meagher, A., Sobczak, S. Wolff, B.G (1996) Chemical composition and potential hazards of electrocautery smoke. Br. J. Surg., 83, 1792 Sato, A. Nakajima, T. (1979) Partition coefficients of some aromatic hydrocarbons and ketones in water, blood and oil. Br. J. ind. Med., 36, 231-234 Sauer, PA. Tyler, E.J. (1995) Heavy metal and volatile organic chemical removal and treatment in on-site waste water infiltration systems. 1. Catch basirrs and septic tanks. Water Air Soil Pollut., 89, 221-232... 

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