Anion acid/base characteristics

Niederer [100] used ion trap mass spectrometry and negative ion chemical ionisation to determine nitro- and oxypolyaromatic hydrocarbons in soils. Meyer et al. [101] have described a simple and reproducible method which provides the simultaneous determination of polycyclic aromatic hydrocarbons and het-eropolycyclic aromatic hydrocarbons (N, S, O) and their metabolites in contaminated soils. Contaminants extracted from the soil sample were separated by polarity and acid-base characteristics using solid-phase extraction on silica gel and a strong basic anion exchange material. A subfraction containing PANHs and neutral metabolites was subsequently fractionated into neutral and basic... 

Table 2.1. Contribution of cations and anions to the acid/base characteristics of aqueous solutions...

The multiphase model can be used to cover various fibre types or mixtures, once their acid-base characteristics (dissociation constants K ) have been determined by titration. The model is independent of the valences of both anions and cations in the... 

As mentioned in the foregoing text, localized corrosion of metals starts with a local breakdown of passive films and localized metal dissolution then occurs at the breakdown site. The local film breakdown is caused by the adsorption of aggressive anions such as chloride ions, CP, which are hard bases. No reliable information is available about the acid-base characteristic of the passive film surface. It is however expected that the breakdown of passive films will be prevented, if some anions or molecules are firmly adsorbed expelling chloride ions from the film surface. In literature, though, we have seen almost no reliable studies on this subject. 

The adsorbent SG(l)-TEPA-propyl is useful in adsorbing anionic copper cyanide complexes from electroplating solutions. Modeling this anionic adsorption phenomena requires the description of copper cyanide ion speciation in the aqueous solution, the acid-base characteristics of the adsorbent, and the complexation reactions between the copper cyanide anions and the protonated ligand sites. Details can be found elsewhere [5,30],... 

Ionic species containing the characteristic cation - e.g. NH4CI - are acids species containing the characteristic anion are bases, e.g. KNH2. 

Acid-base reactions in many solvent systems can be thought of in terms of the characteristic cations and anions of the solvent (see also p. 831)... 

In a related application, polyelectrolyte microgels based on crosslinked cationic poly(allyl amine) and anionic polyfmethacrylic acid-co-epoxypropyl methacrylate) were studied by potentiometry, conductometry and turbidimetry [349]. In their neutralized (salt) form, the microgels fully complexed with linear polyelectrolytes (poly(acrylic acid), poly(acrylic acid-co-acrylamide), and polystyrene sulfonate)) as if the gels were themselves linear. However, if an acid/base reaction occurs between the linear polymers and the gels, it appears that only the surfaces of the gels form complexes. Previous work has addressed the fundamental characteristics of these complexes [350, 351] and has shown preferential complexation of cationic polyelectrolytes with crosslinked car-boxymethyl cellulose versus linear CMC [350], The departure from the 1 1 stoichiometry with the non-neutralized microgels may be due to the collapsed nature of these networks which prevents penetration of water soluble polyelectrolyte. 

Just as the cation produced by dissociation of water (H30+) is the acidic species in aqueous solutions, the NH4+ ion is the acidic species in liquid ammonia. Similarly, the amide ion, NH2, is the base in liquid ammonia just as OH- is the basic species in water. Generalization to other nonaqueous solvents leads to the solvent concept of acid-base behavior. It can be stated simply as follows A substance that increases the concentration of the cation characteristic of the solvent is an acid, and a substance that increases the concentration of the anion characteristic of the solvent is a base. Consequently, NH4C1 is an acid in liquid ammonia, and NaNH2 is a base in that solvent. Neutralization becomes the reaction of the cation and anion characteristic of the particular solvent to produce unionized solvent. For example, in liquid ammonia the following is a neutralization ... 

The chemical, biological, and physical characteristics of the drug substance can be manipulated and hence optimized by conversion to a salt form. Every compound that exhibits acid or base characteristics can participate in salt formation. Various salts of the same compound often behave quite differently because of the physical, chemical, and thermodynamic properties they impart to the parent compound. Table 1 lists the top 10 FDA-approved commercially marketed final drug forms, and Table 2 lists the top 10 salts that are not approved by the FDA but that are in use in other countries. Only salts of organic compounds have been considered here because most drugs are organic-substances. The relative frequency with which each salt type has been used is calculated as a percentage, based on the total number of anionic or cationic salts in use. 

There is no proton. The cation, NO+, must be counted the acid, and the anion, NOg , the base characteristic of the system. Zinc dissolves in liquid N0O4 evolving nitric oxide and forming [N0+]2[Zn(N03)4] . This compound is an acid in dinitrogen tetroxide and reacts with ethylammonium nitrate, a base in the solvent ... 

Abnormalities of acid-base status of the blood are always accompanied by characteristic changes in electrolyte concentrations in the plasma, especially in metabolic acid-base disorders. Hydrogen ions cannot accumulate without concomitant accumulation of anions, such as CL or lactate, or without exchange for cations, such as or NaL Consequently, electrolyte composition of blood serum or plasma is often determined along with measurements of blood gases and pH and to assess acid-base disturbances. 

Arrhenius and Bronsted-Lowry acid-base neutralization reactions all have one thing in common. They involve the reaction of an acid with a base to form a salt that contains the cation characteristic of the base and the anion characteristic of the acid. Water is also usually formed. This is indicated in the formula unit equation. The general form of the net ionic equation, however, is different for different acid-base reactions. The net ionic equations depend on the solubility and extent of ionization or dissociation of each reactant and product. 

HIn represents nonionized acid molecules, and In- represents the anion (conjugate base) of HIn. The essential characteristic of an acid-base indicator is that HIn and In must have quite different colors. The relative amounts of the two species determine the color of the solution. Adding an acid favors the reaction to the left and gives more HIn molecules (color 1). Adding a base favors the reaction to the right and gives more In ions (color 2). The ionization constant expression can be rearranged. 

Pure oxygen-less melts contain no oxide ions in any form, and, therefore, such pure melts cannot serve as donors of O2-. The melts, which are solvents of the second kind, can affect acid-base interaction on their background in two manners by fixation of oxide ions entering in the melt and by solvation of the conjugate acid or base. However, the ionic solvents of the second kind, used in practice for different measurements and applied purposes, contain admixtures of oxide-ion donors, which are formed in the melt from initial admixtures of oxo-anions such as SO4-, COf- or OH-. The second way of appearance of oxide ion admixtures in molten media is characteristic of the melts based on alkali metal halides the process of high-temperature hydrolysis of the said halide melts results in the formation of hydroxide ions and, after their dissociation, of oxide ions ... 

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