Monovalent metal

This discovery of Bollum (11) makes obsolete a number of previous excellent studies including those on mutual interdependence between concentrations of divalent metal, monovalent metal, hydrogen ion, and substrate. Unless the bond affected by the metal in question is specified, an overall rate represents a number with little value. The problem is further complicated by the suspected (by analogy to other nucleases) quantitative changes in requirements for metal ions at different stages of the reaction. So far no such data are available for DNase I. One is tempted to add, luckily, because in view of the uncertainty of qualitative effects such data would hardly be expected to have a long survival time. 

Mechanisms for the toxic effects of inorganic and organic mercury are believed to be similar. It has been suggested that the relative toxicities of the different forms of mercury (e g., metallic, monovalent, and divalent cations and methyl- and phenylmercury compounds) are related, in part, to its differential accumulation in sensitive tissues. This theory is supported by the observation that mercury rapidly accumulates in the kidneys and specific areas of the central nervous system (Rothstein and Hayes 1960 Somjenetal. 1973). 

The cations of non-alkali-metal monovalent azides tend to form directed bonds with partial covalent character. Consequently the molecular packing of these crystals is slightly deformed from those of alkali metal azides with comparable size cations, as is seen in the structures of TIN3 (phase II), AgNa, CuNa, and NH4Na. The ionic radius of the Cu cation is 0.96 A, which is slightly larger than that of Na (0.95 A) and much less than that of (1.33 A). Hence the crystal structure of CuNa is intermediate between the NaNa and KNa types. 

The phenol ionization in EtOH is further promoted by addition of neutral alkaline earth metal salts MgCl2, CaC/2, S rC/2, and Ba(SCN)2. In varying the [ligand]/[M " ] ratio ([ligand] + [Mg ] = 1 mM), the total phenolate concentration reaches a maximum at [ligand]/[M ] = 1 with all the metals. Monovalent alkali metal salts (LiCl, NaCl, KCl, CsCl), on the other hand, do not dispel the phenolic protons of 1 and 2. With crown homologues 3, 4 basic conditions are needed to displace the phenol protons for and The phenol-pendant N4 homologues 5a, 5b do not interact with alkaline earth metal salts in EtOH solution. 

The relative measurement error in concentration, therefore, is determined by the magnitude of the error in measuring the cell s potential and by the charge of the analyte. Representative values are shown in Table 11.7 for ions with charges of+1 and +2, at a temperature of 25 °C. Accuracies of 1-5% for monovalent ions and 2-10% for divalent ions are typical. Although equation 11.22 was developed for membrane electrodes, it also applies to metallic electrodes of the first and second kind when z is replaced by n. 

Oxygen Octahedra. An important group of ferroelectrics is that known as the perovskites. The perfect perovskite stmcture is a simple cubic one as shown in Figure 2, having the general formula ABO, where A is a monovalent or divalent metal such as Na, K, Rb, Ca, Sr, Ba, or Pb, and B is a tetra- or pentavalent cation such as Ti, Sn, Zr, Nb, Ta, or W. The first perovskite ferroelectric to be discovered was barium titanate [12047-27-7] and it is the most thoroughly investigated ferroelectric material (10). 

Departures from the ideal behavior expressed by equation 7 usually are found in alkaline solutions containing alkaH metal ions in appreciable concentration, and often in solutions of strong acids. The supposition that the alkaline error is associated with the development of an imperfect response to alkaH metal ions is substantiated by the successhil design of cation-sensitive electrodes that are used to determine sodium, silver, and other monovalent cations (3). 

The usual valence of indium is three, although monovalent and bivalent compounds of indium with oxygen, halogens, and Group 15 (VA) and 16 (VIA) elements ate well known. The lower valence compounds tend to disproportionate into the trivalent compound and indium metal the trivalent compounds ate stable. 

Mixed oxides of Fe(IV) can be prepared by heating iron(III) oxide with a metal oxide or hydroxide in oxygen at elevated temperatures. These black compounds have general formulas M FeO, M monovalent, or M2Fe04, M divalent, but do not contain discrete [FeOJ" ions. They are readily decomposed by mineral acids to iron(III) and oxygen. 

Orthophosphate salts are generally prepared by the partial or total neutralization of orthophosphoric acid. Phase equiUbrium diagrams are particularly usehil in identifying conditions for the preparation of particular phosphate salts. The solution properties of orthophosphate salts of monovalent cations are distincdy different from those of the polyvalent cations, the latter exhibiting incongment solubiUty in most cases. The commercial phosphates include alkah metal, alkaline-earth, heavy metal, mixed metal, and ammonium salts of phosphoric acid. Sodium phosphates are the most important, followed by calcium, ammonium, and potassium salts. 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

So far, as in Equation (3.33), the hydrolyses of ATP and other high-energy phosphates have been portrayed as simple processes. The situation in a real biological system is far more complex, owing to the operation of several ionic equilibria. First, ATP, ADP, and the other species in Table 3.3 can exist in several different ionization states that must be accounted for in any quantitative analysis. Second, phosphate compounds bind a variety of divalent and monovalent cations with substantial affinity, and the various metal complexes must also be considered in such analyses. Consideration of these special cases makes the quantitative analysis far more realistic. The importance of these multiple equilibria in group transfer reactions is illustrated for the hydrolysis of ATP, but the principles and methods presented are general and can be applied to any similar hydrolysis reaction. 

Most biological environments contain substantial amounts of divalent and monovalent metal ions, including Mg, Ca, Na, K, and so on. What effect do metal ions have on the equilibrium constant for ATP hydrolysis and the... 

When the oxidation product is an /i-type oxide like ZnO, the conditions are reversed (Fig. 1.78). If a monovalent ion like Li enters the oxide layer in place of Zn one free electron (eo) is destroyed. But the product n(Zn 0)n(eo) is fixed by the reaction governing the non-stoichiometry of ZnO. Hence n(Zn O), the concentration of interstitial Zn ions, increases, and the oxidation rate, which depends upon the concentration of these ions in the oxide in equilibrium with metallic Zn, increases. 

The introduction of divalent calcium and barium oxides into frits in preference to monovalent sodium and potassium generally increases water resistance. Furthermore, oxides of tetravalent and pentavalent metals have a favourable effect on the resistance of glasses and enamels to water. The influence of B2O3 and fluorine in the frit upon chemical resistance is variable and is dependent upon the content of them and the balance of the frit constituents, but they usually cause a diminution in resistance. In general, mill-added clay, silica and opaciher increase water resistance provided the firing or fusing of the enamel is at the optimum. 

Slater, J. C., Phys. Rev. 35, 509, "Cohesion in monovalent metals." Connection between molecular-orbital and valence-... 

Luciferase-catalyzed luminescence of luciferin. Odontosyllis luciferin emits light in the presence of Mg2+, molecular oxygen and luciferase. The relationship between the luminescence intensity and the pH of the medium shows a broad optimum (Fig. 7.2.8). The luminescence reaction requires a divalent alkaline earth ion, of which Mg2+ is most effective (optimum concentration 30 mM). Monovalent cations such as Na+, K+, and NH have little effect, and many heavy metal ions, such as Hg2+, Cu2+, Co2+ and Zn2+, are generally inhibitory. The activity of crude preparations of luciferase progressively decreases by repeated dialysis and also by concentrating the solutions under reduced pressure. However, the decreased luciferase activity can be completely restored to the original activity by the addition of 1 mM HCN (added as KCN). The relationship between the concentration of HCN and the luciferase activity is shown in Fig. 7.2.9. Low concentrations of h and K3Fe(CN)6 also enhance luminescence, but their effects are only transient. 

The nature of the Debye-Hiickel equation is that the activity coefficient of a salt depends only on the charges and the ionic strength. The effects, at least in the limit of low ionic strengths, are independent of the chemical identities of the constituents. Thus, one could use N(CH3)4C1, FeS04, or any strong electrolyte for this purpose. Actually, the best choices are those that will be inert chemically and least likely to engage in ionic associations. Therefore, monovalent ions are preferred. Anions like CFjSO, CIO, /7-CIC6H4SO3 are usually chosen, accompanied by alkali metal or similar cations. 

The transition-metal catalyzed decomposition of thiirene dioxides has been also investigated primarily via kinetic studies103. Zerovalent platinum and palladium complexes and monovalent iridium and rhodium complexes were found to affect this process, whereas divalent platinum and palladium had no effect. The kinetic data suggested the mechanism in equation 7. 

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