Extraction study

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

An extractive study of one can enamel in the presence of food-simulating solvents to determine how gamma radiation from a cobalt-60 source altered the nature and amount of extractives of this enamel. 

Cyclodextrin solution for extraction studies was prepared at a concentration of 1.00 x 10" iif by dissolving solid y-CDx in deionized water (Continental Water Systems, Atlanta, Georgia). Fresh solution was prepared daily to prevent bacterial growth and CDx decomposition from interfering with complexation and extraction. Cyclodextrin was purchased from Advanced Separation Technologies, Inc. (Whippany, New Jersey) and was used as received. Solid CDx from one lot number was used for all extractions. 

Extraction studies have also been carried out by grinding the ageing cements and extracting the soluble ions with water (Wilson Kent, 1970 Crisp Wilson, 1974). Ion content was determined using atomic absorption spectroscopy. The experiments give different, but complementary, results to those of Cook (1983), since what is extracted are those ions that have been released from the glass powder but not yet insolubilized by reaction with the polyacid. 

On the other hand, single-residue methods developed by the applicants give basic information about appropriate cleanup steps and specific determination procedures. In addition, not many laboratories other than those from the applicants are able to test the real solvent extraction efficiency. The reason is that extraction studies need radio-labeled incurred residues instead of fortified samples. Hence enforcement methods provided by the manufacturers accelerate the development of methods which meet the needs of (official) food control laboratories. 

In almost all theoretical studies of AGf , it is postulated or tacitly understood that when an ion is transferred across the 0/W interface, it strips off solvated molecules completely, and hence the crystal ionic radius is usually employed for the calculation of AGfr°. Although Abraham and Liszi [17], in considering the transfer between mutually saturated solvents, were aware of the effects of hydration of ions in organic solvents in which water is quite soluble (e.g., 1-octanol, 1-pentanol, and methylisobutyl ketone), they concluded that in solvents such as NB andl,2-DCE, the solubility of water is rather small and most ions in the water-saturated solvent exist as unhydrated entities. However, even a water-immiscible organic solvent such as NB dissolves a considerable amount of water (e.g., ca. 170mM H2O in NB). In such a medium, hydrophilic ions such as Li, Na, Ca, Ba, CH, and Br are selectively solvated by water. This phenomenon has become apparent since at least 1968 by solvent extraction studies with the Karl-Fischer method [35 5]. Rais et al. [35] and Iwachido and coworkers [36-39] determined hydration numbers, i.e., the number of coextracted water molecules, for alkali and alkaline earth metal... 

Denmark 1.5 days after the explosion. Air samples collected at Roskilde, Denmark on April 27-28, contained a mean air concentration of 241Am of 5.2 pBq/m3 (0.14 fCi/m3). In May 1986, the mean concentration was 11 pBq/m3 (0.30 fCi/m3) (Aarkrog 1988). Whereas debris from nuclear weapons testing is injected into the stratosphere, debris from Chernobyl was injected into the troposphere. As the mean residence time in the troposphere is 20-40 days, it would appear that the fallout would have decreased to very low levels by the end of 1986. However, from the levels of other radioactive elements, this was not the case. Sequential extraction studies were performed on aerosols collected in Lithuania after dust storms in September 1992 carried radioactive aerosols to the region from contaminated areas of the Ukraine and Belarus. The fraction distribution of241 Am in the aerosol samples was approximately (fraction, percent) organically-bound, 18% oxide-bound, 10% acid-soluble, 36% and residual, 32% (Lujaniene et al. 1999). Very little americium was found in the more readily extractable exchangeable and water soluble and specifically adsorbed fractions. 

Sarangi, K. Reddy, B. R. Das, R. P. Extraction studies of cobalt (II) and nickel (II) from chloride solutions using Na-cyanex 272. Separation of Co(II)/Ni(II) by the sodium salts of D2EHPA, PC88A and Cyanex 272 and their mixtures. Hydrometallurgy 1999, 52, 253-265. 

Paiva, A. P. Review of recent solvent extraction studies for recovery of silver from aqueous solutions. Solvent Extr. Ion Exch. 2000, 18, 223-271. 

The series of derivatives of diaza-18-crown-6 illustrated by (182) have also been used for extraction studies involving Li+, Na+ and K+ picrates in a CH2Cl2/water system (Cho Chang, 1980). Relative to the parent macrocycle, all the N,/V -derivatives led to enhanced extraction of these ions although the selectivities observed for the parent system were moderated somewhat. 

Halides other than fluoride form very weak complexes in aqueous solution there are no reliable equilibrium constants to be found in the literature. The solution chemistry of aqueous solutions of beryllium chloride, bromide, and iodide have been reviewed previously (9). Some evidence for the formation of thiocyanate complexes was obtained in solvent extraction studies (134). 

In reviewing these results, we would like to emphasize the information they provide about metals deposition chemistry as well as the potential utility of the proposed regeneration process. The metals extraction studies confirm the fact that three distinct phases of vanadium occur on these catalysts and that they are of varying reactivity. By contrast, the nickel removal is essentially complete under similar conditions. We suggest... 

No sulfoxide complexes of osmium have been reported. Unsymmetri-cal dialkyl sulfoxides have been utilized in extraction studies, and methyl-4,8-dimethylnonyl sulfoxide has found application in the extraction of iron (266). Extraction of ruthenium from hydrochloric acid solutions by sulfoxides has been studied (470) and comparisons of sul-fones, sulfoxides, and thioethers as extractants for nitrosoruthenium species reported (441, 443). Similar studies on the extraction of nitro-soosmium species have been reported (442). 

The preliminary study identified approximately 2300 yd3 of contaminated soil with a hot zone of approximately 800 yd3, which required the bulk of remediation effort. A pilot air sparge/soil vapor extraction study was made to define remediation costs. The remediation effort was estimated to extend for 3 years. 

Table I presents an evaluation of Equation 21 based on previously reported values for log Kqw, V, and 6. The constant Cj was calculated from the log KQC of benzene estimated from Figure 2. Estimates of log KQC for the remaining compounds in Table I are presented for 6 equal to 10.3 and 11.5. The value of 10.3 corresponds to the 5p implied from solvent extraction studies (31). In this case,...

Richter, H. G., and J. Irvine jr. Solvent Extraction Studies. Mass. Inst. 

Among the extracts studied, the LC-CHCI3 and LC-alk. (the alkaloid fraction) at 500 mg/kg dose provided 24.3% and 32.1% inhibition, respectively. Successive fractionation of the alkaloid fraction (LC-alk.) by silica gel and Sephadex columns, the best anti-inflammatory effect was observed in three subfractions as LHb.6-8... 

Martinez MA, Sanchez de la Torre C, Almarza E. 2003. A comparative solid-phase extraction study for the simultaneous determination of fluoxetine, amitriptyline, nortriptyline, trimipramine, maprotiline, clomipramine, and trazodone in whole blood by capillary gas-liquid chromatography with nitrogen-phosphorus detection. J Anal Toxicol 27 353. 

The temperature variation method is used often in solvent extraction studies. It can give reliable values of the enthalpy if care is taken to verify that the change in temperature is not causing new reactions, which perturb the system. Also, a reasonable temperature range (e.g., AT 50°C) should be used so that it is possible to ascertain the linearity of the In P vs. l/T plot upon which Eq. (3.17) is based. 

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