Bottom developer-soluble

Purification of anthracene. Dissolve 0-3 g. of crude anthracene (usually yellowish in colour) in 160-200 ml. of hexane, and pass the solution through a column of activated alumina (1 5-2 X 8-10 cm.). Develop the chromatogram with 100 ml. of hexane. Examine the column in the hght of an ultra-violet lamp. A narrow, deep blue fluorescent zone (due to carbazole, m.p. 238°) will be seen near the top of the column. Immediately below this there is a yellow, non-fluorescent zone, due to naphthacene (m.p. 337°). The anthracene forms a broad, blue-violet fluorescent zone in the lower part of the column. Continue the development with hexane until fluorescent material commences to pass into the filtrate. Reject the first runnings which contain soluble impurities and yield a paraffin-hke substance upon evaporation. Now elute the column with hexane-benzene (1 1) until the yellow zone reaches the bottom region of the column. Upon concentration of the filtrate, pure anthracene, m.p. 215-216°, which is fluorescent in dayhght, is obtained. The experiment may be repeated several times in order to obtain a moderate quantity of material. 

Zebrafish embryo assay results were compared to the ToxCast in vitro assay features from the predictive model of developmental toxicity (50). A majority of the features were significant between the zebrafish data and predictive models, despite the fact that the zebrafish assay did not correlate with global developmental toxicity defined by species-specific ToxRefDB data. The top 15 chemicals predicted to be developmental toxicants and bottom 15 chemicals predicted not to be developmental toxicants varied in their endpoint responses and logP values. Padilla et al. (35) noted that chemical-physical characteristics could limit the amount of chemical seen by the embryo due to poor solubility or poor uptake. This may be the reason that a majority of the bottom 15 chemicals with no zebrafish embryo activity had logP values less than 1.0. The bottom 15 chemicals with zebrafish embryo activity could almost exclusively be characterized by the negative predictors of the species-specific developmental toxicity models, which may be indicating that these predictors have differing roles between mammalian and zebrafish development. 

In addition to concerns over the incomplete solubility of some of the H-coal vacuum-still bottom materials in toluene, the precipitation experiments just discussed are subject to problems associated with two-phase reactions in general. Incomplete contact between the organic compounds in toluene solution and the aqueous acids can lead to inconsistent precipitation results. With this in mind, a different approach was developed in which various H-coal vacuum-still bottoms were treated with phosphotungstic acid, which is soluble in tetrahydrofuran. This reagent allows precipitation to be accomplished from an initially one-phase system, and gives rise to crisp, easily collected salts. 

A second process using complex as the catalyst was independently developed by the Standard Oil Company (Indiana) and by the Texas Company (25,26). A simplified flow diagram of this liquid-phase process is shown in Figure 17. A portion of the dried and heated feed passes through a saturator where aluminum chloride is picked up in accordance with the solubility curve shown in Figure 8. The total feed combined with re( y< le hydrogen chloride enters the bottom of the reactor and... 

DNAPL located at the bottom of an aquifer serves as a source of pollution to groundwater flowing past. Considering the low solubility of many chlorinated solvents and the unacceptability of their presence at concentrations higher than a few parts per billion, it is apparent that even a relatively small volume of DNAPL can contaminate an immense volume of groundwater unfortunately, centuries or even millennia may be required for the ultimate removal of DNAPL from an aquifer under natural conditions. DNAPL also commonly will enter channels, fractures, holes, and cracks in an underlying aquitard or aquiclude, thereby sinking even farther (see Fig. 3-26). No satisfactory technique has yet been developed to locate DNAPL in bedrock fractures, much less to predict its movement. 

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