Cation-acid anion complexes

The stability of all cation-acid anion complexes [CA(OAA)] is described by a reaction of the general form ... 

Fig. 10. Effect of increasing pC02 on the stability of calcite in the presence of acetic acid. As the acetic acid concentration increases, the buffering capacity of the water increases with respect to the water s ability to consume protons and resist pH change. Thus, at a critical acetic acid concentration (about 0.07 mol 1 4200mgkg ) increases in acidity caused by dissolving CO2 in the water can be offset by the consumption of by the acetic acid-acetate reaction. At lower acetic acid concentrations calcite dissolves, whereas at higher aceteic acid concnetrations calcite may precipitate (Lundegard and Land 1989). Solid symbols are data from Thyne (1992) as shown in Fig. 11. Discrepant predictions between the two studies at the lower acid concentration can be reconciled by a higher concentration of cation-acid anion complexes in Thyne s study. These complexes release cations that cause carbonate mineral precipitiation. The absolute amount of solid formation cannot be calculated from Thyne s data...

The most common oxidation state of niobium is +5, although many anhydrous compounds have been made with lower oxidation states, notably +4 and +3, and Nb can be reduced in aqueous solution to Nb by zinc. The aqueous chemistry primarily involves halo- and organic acid anionic complexes. Virtually no cationic chemistry exists because of the irreversible hydrolysis of the cation in dilute solutions. Metal—metal bonding is common. Extensive polymeric anions form. Niobium resembles tantalum and titanium in its chemistry, and separation from these elements is difficult. In the soHd state, niobium has the same atomic radius as tantalum and essentially the same ionic radius as well, ie, Nb Ta = 68 pm. This is the same size as Ti ... 

Complexation of metal cations and transport in ore-forming solutions derived from sedimentary basins by organic acid anionic complexes present in oil field brines... 

Indium nitrate can be prepared from InCl3 and N205 158,159 the dissolution of indium metal in cone, nitric acid yields In(N03) xH20 (x = 3, 4, 5),7 which has been used as the source of cationic and anionic complexes.64 Salts of [In(N03)4] have been reported,64160 and Raman studies161,162 have demonstrated the presence of In/NOj complexes in solution the stability constant results have been reviewed.9... 

Ion chromatographic methods have been described for the co-determination of anions and cations in rainwater. Thus Jones and Tarter [138], using the conditions given in Table 2.19 reported determinations down to lmg L 1 of anions (chloride, bromide and sulphate) and cations (sodium, potassium, magnesium and calcium) in rainwater without converting the cations to anion complexes prior to detection [139], The technique uses a cation separator column, a conductivity detector, an anion suppressor column, and either a second conductivity detector or an electrochemical detector in sequence. The use of different eluants provides a means for the detection of monovalent cations and anions and divalent cations and anions in each of the samples. Using an eluant with a basic pH, it is possible to separate simultaneously and detect the monovalent cations (with the exception of the ammonium ion) and anions, while an eluant with an acidic pH allows for the separation and detection of divalent cations and anions. 

Traditionally papermaking is made at acid pH of about 4.5. Because of this the sizing of paper is carried out with resin acid salts in the presence of alum. Under these conditions, the resin acid anions complex with the aluminium cations and the complex formed is attracted to and deposited on the fibre surface. The purpose of sizing is to render the paper more resistant to water-based printer s ink. Today there is much interest in so-called alkaline sizing at about pH 7, which is preferred for specialist long-life papers. Here sizes such as alkyl ketene dimer replace alum. Alkaline papermaking has the further advantage that fillers such as calcium carbonate can be employed. 

The fluoride ion chemisorbs on clays and oxides by ligand exchange of surface OH", a reaction favored at low pH and on oxide and silicate minerals of low crystallinity. Fluoride, a hard base, has a particular affinity for a hard acid. Soluble AP -fluoride cationic and anionic complexes are quite stable, and can dominate the speciation of dissolved aluminum in low-humus soils. The mobility of A1 can be increased by the presence of F soluble complex formation with A1 may explain the rather high solubility and mobility of F in acid soils. 

Hence mercury is a poor reducing agent it is unlikely to be attacked by acids unless these have oxidising properties (for example nitric acid), or unless the acid anion has the power to form complexes with one or both mercury cations or Hg]", so altering the... 

Iron hahdes react with haHde salts to afford anionic haHde complexes. Because kon(III) is a hard acid, the complexes that it forms are most stable with F and decrease ki both coordination number and stabiHty with heavier haHdes. No stable F complexes are known. [FeF (H20)] is the predominant kon fluoride species ki aqueous solution. The [FeF ] ion can be prepared ki fused salts. Whereas six-coordinate [FeCy is known, four-coordinate complexes are favored for chloride. Salts of tetrahedral [FeCfy] can be isolated if large cations such as tetraphenfyarsonium or tetra alkylammonium are used. [FeBrJ is known but is thermally unstable and disproportionates to kon(II) and bromine. Complex anions of kon(II) hahdes are less common. [FeCfy] has been obtained from FeCfy by reaction with alkaH metal chlorides ki the melt or with tetraethyl ammonium chloride ki deoxygenated ethanol. 

Plutonium(III) in aqueous solution, Pu " ( 4)> is pale blue. Aqueous plutonium(IV) is tan or brown the nitrate complex is green. Pu(V) is pale red-violet or pink in aqueous solution and is beUeved to be the ion PuO Pu(VI) is tan or orange in acid solution, and exists as the ion PuO. In neutral or basic solution Pu(VI) is yellow cationic and anionic hydrolysis complexes form. Pu(VII) has been described as blue-black. Its stmcture is unknown but may be the same as the six-coordinate NpO (OH) (91). Aqueous solutions of each oxidation state can be prepared by chemical oxidants or reductants... 

Adsorption of Metal Ions and Ligands. The sohd—solution interface is of greatest importance in regulating the concentration of aquatic solutes and pollutants. Suspended inorganic and organic particles and biomass, sediments, soils, and minerals, eg, in aquifers and infiltration systems, act as adsorbents. The reactions occurring at interfaces can be described with the help of surface-chemical theories (surface complex formation) (25). The adsorption of polar substances, eg, metal cations, M, anions. A, and weak acids, HA, on hydrous oxide, clay, or organically coated surfaces may be described in terms of surface-coordination reactions ... 

Catalytic curing agents initiate resin homopolymerization, either cationic or anionic, as a consequence of using a Lewis acid or base in the curing process. The Lewis acid catalysts frequently employed are complexes of boron trifluoride with amines or ethers. 

In this way hosts 141-145 with both a cr-bonded Lewis acidic boron atom for complexation of anions and a conventional multidentate ligand for cations are generated. Complexation experiments of the 21-membered crown [6] boronate 142 with different potassium salts KX (X = F, Cl, Br, I, SCN, CN, OMe) indicate that there is a high specificity for the incorporation of KF, whereby F is bound covalently to the boron atom and is complexed by the crown ether (146, Fig. 39). An X-ray study has shown that the complexation of KF is heterotopic, i.e., both ions are complexed inside the same host. Some of the salts can only be bound in a monotopic way (KI and KSCN) [237]. 

Cement-forming liquids are strongly hydrogen-bonded and viscous. According to Wilson (1968), they must (1) have sufficient addity to decompose the basic powder and liberate cement-forming cations, (2) contain an acid anion which forms stable complexes with these cations and (3) act as a medium for the reaction and (4) solvate the reaction products. 

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