Some Case Studies

Some Case Studies 1. The dissociation of acetic acid 

The dissociation of acetic acid in aqueous solution is an example of the simplest type of protolytic process. The dissociation constant was one of the first chemical parameters to be studied as a function of isotopic composition of the solvent (La Mer and Chittum, 1936 Homel and Butler, 1936), and the determinations have been repeated by several groups of workers. Conductivity measurements (La Mer and Chittum, 1936), potentiometry using the quinhydrone electrode (Korman and La Mer, 1936) or glass electrodes (Salomaa et al., 1964a Gold and Lowe, 1968), and measurements of the rate of a hydrogen-ion 

The main sets of results are reproduced in Fig. 2. The solid line represents equation (31) based on the value for Kn/KB by Gary et oil. (1964a). The empirical equation of the best curve through the data of 

Gold and Lowe (1968) and fixed at its extremes by the KsjKX) ratio of Gary et al. is  

A more critical test of the same data is shown in Fig. 3 where the points now represent the difference between determined pisT-values and the predictions of equation (119). Generally very satisfactory agreement between the results of the two sets of potentiometric studies with the glass electrode and those of the two conductivity studies is seen to exist. There is virtually a random scatter of all these points about the prediction from equation (119). The kinetic data (Brescia and La Mer, 1938) also fit in reasonably well, although they show some larger deviations and less good reproducibility, especially for large values of n. 

No case study is exactly like another case. Each case study has its own features, defined by the natural setting and the nature of data obtained. The following case studies are an assortment of studies, heavily based on chemical data. 

Cotecchia et al. (1974) studied the salinization of wells on the coast of the Ionian Sea. A fingerprint diagram (Fig. 6.23) served to define a conceptual model. The lowest line (MT) is of a fresh water spring and the uppermost line (I.S.) is of the Ionian Sea water. The lines in between (SR and CH) are of groundwaters with increasing proportions of seawater intrusion. The CH well met the nondiluted seawater at a depth of 170 m. This interpretation seems to be well founded as it is based on six dissolved ions. The whole story is condensed into one fingerprint diagram. 

2 Classification into Lithologically Controlled Geochemical Water Groups 

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3 Solubility Control of Groundwater Chemistry in an Arid Region 

But factors other than the surface charge can become important such as the effects of specific adsorption of cations and anions on the degree of surface protonation (see Example 5.1). 

Most oxides show, in accordance with the general rate equation (5.16) the same trend with regard to the rate dependence on pH a decrease in pH in the acid range and an increase in pH in the alkaline range. 

vitreous silica in 0.7 M NaCI solution (Wirth and Gieskes, 1979)  

The dissolution of quartz is accelerated by bi- or multidentate ligands such as oxalate or citrate at neutral pH-values. The effect is due to surface complex formation of these ligands to the Si02-surface (Bennett, 1991). In the higher pH-range the dissolution of quartz is increased by alkali cations (Bennett, 1991). Most likely these cations can form inner-spheric complexes with the =SiO groups. Such a complex formation is accompanied by a deprotonation of the oxygen atoms in the surface lattice (see Examples 2.4 and 5.1). This increase in C H leads to an increase in dissolution rate (see Fig. 5.9c). 

HCO 3 enhances the Dissolution Rate of Hematite. Fe(III) in natural waters is present as hydroxo complexes, especially Fe(OH) , Fe(OH)3(aq), Fe(OH)4. In addition a carbonato complex - Fe(C03)2 - is present in seawater and at the surface of solid iron(III)(hydr)oxides. Fig. 5.11 shows the dependence of the dissolution rate as a function of the hydrogen carbonato surface complex 

Doubts as to which component of the electrolyte solution is the electroactive species seem to arise predominantly in anodic reactions this is quite natural in view of the range of useful anions, spanning a range of oxidation potentials between 0 and 3-5 V, available for 

1 p/2 is the so-called half peak potential, measured on peak voltammograms as the potential at half the peak current. 

As a prelude to the discussion of some anodic reactions, Table 8 shows the present state of knowledge with respect to the electroactive species in a number of representative anodic reactions of different types. 

Perusal of Table 8 reveals that the problem of identifying the electroactive species is not solved for a number of reactions (nos. 3, 5, 23, 27, 28, 29) and that recent work utilizing modern electrochemical techniques has revived the discussion of some important ones (nos. 14, 15) and paved the way for renewed attempts at mechanistic discrimination. We shall deal with some of these reactions in the following discussion. 

Nature of the Electroactive Species in Some Anodic Reactions of Different Types 

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In the next chapter we shall look at some case studies in corrosion-resistant designs which are based on the ideas we have just discussed. 

Instead of listing results of all these different experiments on the large variety of possible materials we will focus on some case studies which might serve as model systems for a given... 

An immense number of phosphine complexes of rhodium have been synthesized and detailed compilations of information are available [3d]. In this section, some case studies are presented to illustrate the variations that arise as a result of changes in the steric requirements of the phosphine. 

In this section we are going to look at some case studies to see how hplc experimental methods are developed. 1 am not going to give a long list of applications, because these are easy to find elsewhere, and sometimes do not make very interesting reading. Most textbooks on hplc have lists of applications, eg the book by Hamilton and Sewell (2nd Edn, Chapter 8), and applications can also be obtained from a number of journals (eg Analytical Chemistry annual reviews). 

The following subsections describe some case studies dealing with GC/MS procedures used to investigate lipid materials in archaeological objects and paintings. 

The following paragraphs describe some case studies related to procedures based on GC/MS techniques to archaeological and art objects. 

Table 2.10 provides some case studies of IGCC projects that are described on the following url address http //europe. eu.int/comm/energy transport/atlas/html/cccasestudies.html. 

An introductory manual that explains the basic concepts of chemistry behind scientific analytical techniques and that reviews their application to archaeology. It explains key terminology, outlines the procedures to be followed in order to produce good data, and describes the function of the basic instrumentation required to carry out those procedures. The manual contains chapters on the basic chemistry and physics necessary to understand the techniques used in analytical chemistry, with more detailed chapters on atomic absorption, inductively coupled plasma emission spectroscopy, neutron activation analysis, X-ray fluorescence, electron microscopy, infrared and Raman spectroscopy, and mass spectrometry. Each chapter describes the operation of the instruments, some hints on the practicalities, and a review of the application of the technique to archaeology, including some case studies. With guides to further reading on the topic, it is an essential tool for practitioners, researchers, and advanced students alike. 

The objective of this book is to help form a more clear perspective of product design through case studies from people with different backgrounds. Products ranging from molecules to structured products are considered. Also, some cases studies involve products that have been commercialized, while some are student... 

PHYTOREMEDIATION - SOME CASE STUDIES CONDUCTED ATWAU... 

Three- or more-level response surface designs, such as three-level full factorial, central composite (CCD), and Box-Behnken designs, are applied in some case studies. 

Some case studies suggest that dermal exposure to the vapor of diesel fuel may also result in absorption via the skin. The studies identify one individual with only vapor exposure and two others with vapor and/or direct dermal contact with diesel fuel individuals developed acute renal failure or renal necrosis (Barrientos et al. 1977 Crisp et al. 1979 Reidenberg et al. 1964). Also, dermal exposures to marine diesel fuel and JP-5 in mice induced renal damage (Basely et al. 1982). No studies were located that directly tested dermal absorption of fuel oil vapor. 

Sources, Ambient Levels, Transport, and Transformation Some Case Studies... 

Let us now consider some case studies of PAHs and PACs in ambient air. A number of studies of bacterial mutagenicity of fine ambient aerosols (primary and... 

In this chapter we present some case studies that will allow us to examine how the concepts we have described in the previous chapters can be applied to solving real, materials-related problems. We begin with a description of some basic design principles, which will lead into how they can be adapted to materials selection. 

Stockdale, E.A. and Cookson, W.R. 2003. Sustainable farming systems and their impact on soil biological fertility - some case studies. In Abbott L.K. and Murphy, D.V. (eds) Soil Biological Fertility - A Key to Sustainable Land Use in Agriculture. Kluwer Academic Publishers, The Netherlands, pp. 225-239. 

Finally, in Part V we present some case studies aimed at illustrating how to combine all the theories and concepts developed throughout the book. The environmental systems that we have chosen to do this include lakes (Chapter 23), rivers (chapter 24), and aquifers (chapter 25). These cases will also demonstrate how far one can go with simple models that do not need a large computer but just rely on the mathematical understanding of the user and perhaps on a simple pocket calculator to get quantitative results. 

Parry M. Norling, RAND What can we say about innovation in the public sector A government agency recently asked RAND how it might be more innovative in all the work it does, not only in research and development (R D), and requested some case studies of a number of public- and private-sector organizations known to be quite innovative. 

Some case studies are included to provide examples and also demonstrate some of the more important issues. 

It is outside the scope of this report to establish the group to which every existing biomarker of exposure belongs according to the framework presented. Furthermore, the group designation has to be contextualized to a study s objectives, as stated previously. Some case studies will be presented in Chapter 5, however, to illustrate the potential usefulness of the framework. 

Analytical gradients and Hessians are available for CASSCF, and it is expected that this technology will be extended to the MR-CI and MP2 methods soon. Further, by virtue of the multireference approach, a balanced description of ground and excited states is achieved. Unfortunately, unlike black boxes such as first-order response methods (e.g., time-dependent DFT), CAS-based methods require considerable skill and experience to use effectively. In the last section of this chapter, we will present some case studies that serve to illustrate the main conceptual issues related to computation of excited state potential surfaces. The reader who is contemplating performing computations is urged to study some of the cited papers to appreciate the practical issues. 

Mechanistic Organic Photochemistry Some Case Studies 121... 

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