Water extraction constants

Catalyst Cation. The logarithms of extraction constants for symmetrical tetra- -alkylammonium salts (log rise by ca 0.54 per added C atom. Although absolute numerical values for extraction coefficients are vastly different in various solvents and for various anions, this relation holds as a first approximation for most solvent—water combinations tested and for many anions. It is important to note, however, that the lipophilicity of phenyl and benzyl groups carrying ammonium salts is much lower than the number of C atoms might suggest. Benzyl is extracted between / -propyl and -butyl. The extraction constants of tetra- -butylammonium salts are about 140 times larger than the constants for tetra- -propylammonium salts of the same anion in the same solvent—water system. 

Table 1. Anion Extraction Constants Eq, of Tetra-n-Butylammonium Ion Pairs Between Water and Chloroform...

The TIC trace from the LC-MS analysis of an extracted river water sample, spiked with 3 p.g dm of atrazine and three of its degradation products, is shown in Figure 3.30. The presence of significant levels of background makes confirmation of the presence of any materials related to atrazine very difficult. The TIC traces from the constant-neutral-loss scan for 42 Da and the precursor-ion scan for m/z 68 are shown in Figure 3.31 and allow the signals from the target compounds to be located readily. 

The catalyst anion has also been shown to have a large influence on the reaction rate. The extraction constant of tetra-n-butylammonium salts between water and chloroform decreases with different anions as follows picrate CIO4 > T > toluene sulphonate > NO.-i > Br > benzoate > Cf > acetate > OH (Esikova, 1997 Dehmlow, 1993). 

Cote, G. Jakubiak, A. Bauer, D. Szymanowski, J. Mokili, B. Poitrenaud, C. Modeling of extraction equilibrium for copper(II) extraction bypyridinecarboxylic acid esters from concentrated chloride solutions at constant water activity and constant total concentration of ionic or molecular species dissolved in the aqueous solution. Solvent Extr. 

The alternative approach draws form the experience of coffee decaffeination. The currently practiced process is carried out on a massive scale using scC02 to extract the caffeine from the coffee beans. The caffeine is not precipitated from the scC02 by decompression, but is extracted into water from which it can be separated. The great advantage of this process is that it can be operated at essentially constant pressure and... 

Table I. Extraction Constants for the Transfer of Permanganate from Water into Methylene Chloride (32)...

For a two phase system (water and a water nonmiscible organic solvent) containing a hydrophobic salt QX dissolved in water (Q + X QXs), the conditional extraction constant e is defined Cqxs = QX[Q ]w [X 1w where Cqxs is the total concentration of Q (quat) and X (corresponding anion) present in the organic phase in the molar ratio 1 to 1 and [Q ]w [X ]w te the respective... 

The salts of the series are bright red crystalline bodies. They are soluble in water, neutral in reaction, and dilute mineral acids do not transform them into aquo-salts. The least soluble member of the series is the sulphate [(NH3)4Co (OH)2 Co(NH3)4](S04)a.2H30, which is prepared by heating hydroxo-aquo-tetrammino-cobaltic sulphate at 100° C. till it is constant in weight. The mass is extracted with water and the sparingly soluble sulphate collected and dried. The crude product so obtained is converted into the chloride and an aqueous solution of this then treated with a solution of sodium sulphate, when a crystalline precipitate of the diol-sulphate is obtained. It is collected, washed with water, alcohol, and finally with ether. It forms small red needle-shaped crystals which contain two molecules of water of hydration. 

Conclusions. A sampling and analytical method for two chlorinated isocyanuric acids, NaDCC and TCCA, in air has been described. Briefly, these acids can be collected from air with DM-5000 (PVC copolymer) filters. The filter samples are extracted with water and titrated against sodium thiosulfate using constant-current potentiometry. The titration method will neither separate or distinguish NaDCC in the presence of TCCA or the reverse. The identity of either compound must be known in the workplace environment along with the identities of any other interfering... 

In a 1-1. three-necked round-bottomed flask fitted with a Hershberg stirrer and a constant water separator (Note 1) surmounted by a reflux condenser are placed 120 g. (1 mole) of acetophenone, 113 g. (1 mole) of ethyl cyanoacetate (Note 2), 15.4 g. (0.2 mole) of ammonium acetate, 48.0 g. (0.8 mole) of glacial acetic acid, and 200 ml. of benzene. The reaction mixture is stirred and heated under reflux for 9 hours during which time 28-33 ml. of lower layer is collected in the water separator (Note 3). To the cooled reaction mixture is added 100 ml. of benzene, and the whole is extracted with three 10()-ml. portions of water. The combined aqueous layers arc extracted with 30 ml. of benzene, which is then added lo the organic layer from the previous... 

Formally, complexation stability constants in water (log K) and extraction constants (logA j.J can be related via partitioning coefficients of the free ligand and its complex between the aqueous and organic phases.16 However, the latter are rarely available, and therefore the relationships between log/f and log Ktx are not widely used. Nevertheless, in many cases, the binding ability of ligands to metal in complexation and extraction processes follows the same trend. In this respect, information... 

Figure 4. Expanded regions of H NMR spectra recorded from extracts of (a) a soil sample (pH 8.2), (b) a blank soil sample in the Fourth Official OPCW Proficiency Test (May 1998). The soils were extracted with water, the extract was concentrated, and the remaining water was replaced with D20, and (c) spectrum of authentic thiodiglycol (pH 6.3) in D20, which was identified in the soil sample. The H chemical shifts were 2.763 and 3.758 in (a) and 2.757 and 3.755 in (c) the coupling constant was 6.3 Hz in both spectra. The experimental conditions in all spectra were similar...

The association constant for ion binding of Cyclo-(Pro-Gly)3 b nearly the same as that of antamanide, but the selectivity for Ca of Cydo-(Pro-Gly)3 is inferior to that for Na" " of antamanide (144). Cyclo-(Pro-Gly)3 resembles the K -specific cyclic hexadepdpeptide aiitibiotic enniatin (145), in the aspect that both cycUc compounds form sandwich-type comjdexes with ions. It is very likely that Cyclo-(Pro y)3 transports ions across a membrane vb the formation of a club sandwich-type complex. The metal-ion complex of Cyclo-(Pro<]tly)3 is extractable with water from organic phase. A specific behavior of clo-(Pro-Gly)3 in the ion tran rt throu a membrane b expected from fhb property. 

The Soxhlet and distillation experiments were carried out at an elevated temperature. The Soxhlet apparatus consists of an Allyhn condenser, a Soxhlet extraction tube, an extraction thimble for holding the sludge sample, and a 250 mb flask. Approximately 200 mLof hexane was used the extraction medium. A constant water temperature of 348 K was used to vaporize the hexane in the flask. The hexane vapor was condensed, percolated through the sludge sample, and returned to the flask. This process was repeated for 4 hours. The hexane extract in the flask was subsequently analysed for PCB content. 

The use of modifiers occasionally improves the extraction process. Water as extractant can be modified with organic solvents such as methanol, acetone or acetonitrile in low proportions (< 5%) in order to decrease its dielectric constant — and hence its polarity — without the need for a drastic temperature increase [37]. Also, an acid or base can be used to alter the pH in those cases where it significantly influences the extraetion yield [29,46]. On the other hand, surfactants facilitate the extraction of non-polar compounds by formation of micelles [47]. Modifiers are less frequently used with extractants other than water. One example is the addition of sodium acetate to methanol to extract organotins (OTs) the additive increases the efficiency in two ways, namely (a) acetate ion by complexing OTs and (b) sodium ion through cation exchange of OTs sorbed to the clay fraction of sediments [21]. 

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