Effect of organic impurities

In Fig. II the effect of plasticizer is shown for the system poly(vinyl chloride)/tricresyl phosphate. Water also affects the conductivity considerably but its precise function is by no means clear particularly at low moisture contents (135). The presence of ionic impurities causes increased conductivity but the effect of organic impurities is less apparent. For instance, the addition of plasticizers of differing purity to poly-... 

All of these changes in ciystal habit caused by kinetic factors are drastically effected by the presence of impurities that adsorb specifically to one or another face of a growing ciystal. The first example of crystal habit modification was described in 1783 by Rome de Lisle [77], in which urine was added to a saturated solution d NaCl changing the crystal habit from cubes to octahedra. A similar discovery was made by Leblanc [78] in 1788 when alum cubes were changed to octahedra by the addition of urine. Buckley [65] studied the effect of organic impurities on the growth of inoiganic crystals from aqueous solution, and in Mullin s book [66] he discusses the industrial importance of this practice. 

Y. Jiang, W. Wang, V. R. R. Marthala, J. Huang, B. Sulikowski, M. Hunger, Effect of organic impurities on the hydrocarbon formation via the decomposition of surface methoxy groups on acidic zeolite catalysts, J. Catal., 2006, 238, 21-27. 

Law WL, Platt AM, Wimalaratne PDC, Blair SL (2009) Effect of organic impurities on the performance of direct formic acid fuel cells. J Electrochem Soc 156 B553-B557... 

Kuznetsov, V.A., Okhrimenko, T.M. and Rak, M., 1998, Growth promoting effect of organic impurities on growth kinetics of KAP and KDP crystals, J. Crystal Growth, 193,164. 

Commercial carbon black is a spherical colloidal form of nearly pure carbon particles and aggregates with trace amounts of organic impurities adsorbed on the surface. Potential health effects usually are attributed to these impurities rather than to the carbon itself. Soots, by contrast, contain mixmres of particulate carbon, resins, tars, and so on, in a nonadsorbed state. ... 

Smernik, R. J., and Oades, J. M. (2000a). The use of spin counting for determining quantitation in solid state C-13 NMR spectra of natural organic matter 1. Model systems and the effects of paramagnetic impurities. Geoderma 96,101-129. 

The Difasol reaction involves a mechanically stirred reactor and settlers. An injection of fresh catalyst components is defined to compensate the detrimental effects of accidental impurities present in the feed and slight carryover of the catalyst. Mixing of the solvent phase with the organic phase ensures advantageous butene conversion. However, importantly, the stirring power combined with a high... 

Figure 8.19. Four chromatograms illustrating the effect of organic modifier in MPB, showing the selectivity effect of several impurities.

Small amounts of organic materials may produce marked changes in the CMC in aqueous media. Since some of these materials may be present as impurities or byproducts of the manufacture of surfactants, their presence may cause significant differences in supposedly similar commercial surfactants. A knowledge of the effects of organic materials on the CMC of surfactants is therefore of great importance for both theoretical and practical purposes. 

The evidence for the ferryl ion is at present not very conclusive. Kolthoff and Medalia (58) have observed that there is no salt effect on the Fenton oxidation of alcohol and conclude that this argues against the participation of a charged reactant such as ferryl ion with ferrous ion in reaction (1). However, as we have seen for the iodide reaction, such evidence is of doubtful significance unless very low salt concentrations are used. On the other hand, some observations of Barb et al. on the oxidation of organic impurities as well as the above discrepancy in the determination of ki/ki can be interpreted in terms of the ferryl ion. 

This type of activity might be considered as updating the organic textbooks. Such sessions include information on how to improve yields in various types of reactions using the intermediate, what catalysts to use for certain types of reactions, and the effect of possible impurities on the yield and on the catalyst life. 

Chloride ions are used in the Fricke dosimeter as hydroxyl radical scavengers (2). Since adding chloride ions does not decrease the yield of ferric ion (except in the presence of organic impurities), it can be argued that chlorine atoms and hence Cl2" radical ions react to oxidize ferrous ion. Using the present technique we have measured the effect of ferrous ions on the rate of decay of the Cl2" transient. Ferrous ions increased this rate, and a rate constant for Reaction 3 was determined h = 3.8 0.3 X 107M 1 sec."1 at pH 2.1... 

It has been shown (Bartlett and McCollum, 1956) that the presence of organic impurities or cosolvents in aqueous sulfuric acid can have very powerful effects on the observed concentration ratio for nitroaniline indicators. It is not, therefore, surprising that if [eqn (1)] is present in concentrations much greater than lO-2 M, it may begin to affect its own ionization ratio through solute-solute interactions. Hammett anticipated and avoided this problem by exploiting the high molar absorptivities of his nitroanilines. in order to keep them at very low concentration where their influence on... 

The biphasic system has been evaluated in terms of activity, selectivity, recyclability and lifetime of the ionic liquid, in a continuous flow pilot operation. A representative industrial feed (Raffinate II), composed of 70 wt.% butenes (27% of which is 1-butene) and 1.5 wt.% isobutene (the remainder being n-butane and isobutane) enters continuously into the well mixed reactor containing the ionic liquid and the nickel catalyst. Injection of fresh catalyst components can be made to compensate for the detrimental effects of random impurities present in the feed and for a slight catalyst carryover by the organic phase. The reactor is operated... 

In our experience, in addition to moisture, commercial methanol may also contain of organic impurities such as acetone, formaldehyde, ethanol, methyl formate and even acetaldehyde. The water content can be reduced to less than 0.01% by fractional distillation. Further drying may be effected with calcium hydride or calcium sulphate, but most efficiently with metallic sodium. Experiments in this laboratory showed that treatment with sodium, twice repeated, decreased the water content to S x 10 %. If a larger amount of acetone is present as an impurity, it can be precipitated first in the form of iodoform, by treatment with iodine and sodium hydroxide. Methanol is then distilled off from the precipitate, and the dehydration process is performed afterwards. 

Feed stream impurities mainly in the hydrogen fuel fed to the anode electrode can cause both temporary and permanent performance degradation in PEMFCs. Steam reformation to produce hydrogen fuel inevitably leads to the presence of these impurities such as CO, HjS, NHj, organic sulfur-carbon, and carbon hydrogen compounds. The effects of these impurities in the fuel gas supply to the PEMFC have been well documented and studied in peer-review hterature (Garzon et al., 2009). 

Access to the low-wavenumber regions of the vibrational Raman spectra of minerals and solids of geological relevance have yielded information on crystal lattice symmetries and on the effect of ionic impurities. Databases of geological materials now rival those of organic compounds and affiliations to solid-state physics, crystal engineering and to substrate characterization for thin-film devices are numerous. 

Similar as inorganic semiconductors, impurities are an important factor that can change the energy level and the charge transport properties in organic semiconductors including photoconducting DLCs. The effect of the impurity, i.e. the other component of the system, depends on the nature of the impurity. 

Strong electron-donors or acceptors can effect charge transfer with insulating polymers and produce some increase in conductivity, e.g. from 10" S cm to 10" -10" Scm" for PS films exposed to iodine. This can be attributed to carrier hopping between localized charge-transfer sites, e.g. the pendant groups. The effect of organic and ionic impurities is particularly important in polymer films used as insulation and protective layers in semiconductor devices. This has been studied for various poly(ester imide)s by measurement of the residual current in a field-effect transistor (FET) coated with impurity-doped polymer. ... 

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