Metal concentration effect

Qua.driva.Ient, Zirconium tetrafluoride is prepared by fluorination of zirconium metal, but this is hampered by the low volatility of the tetrafluoride which coats the surface of the metal. An effective method is the halogen exchange between flowing hydrogen fluoride gas and zirconium tetrachloride at 300°C. Large volumes are produced by the addition of concentrated hydrofluoric acid to a concentrated nitric acid solution of zirconium zirconium tetrafluoride monohydrate [14956-11-3] precipitates (69). The recovered crystals ate dried and treated with hydrogen fluoride gas at 450°C in a fluid-bed reactor. The thermal dissociation of fluorozirconates also yields zirconium tetrafluoride. 

Various other observations of Krapcho and Bothner-By are accommodated by the radical-anion reduction mechanism. Thus, the position of the initial equilibrium [Eq. (3g)] would be expected to be determined by the reduction potential of the metal and the oxidation potential of the aromatic compound. In spite of small differences in their reduction potentials, lithium, sodium, potassium and calcium afford sufficiently high concentrations of the radical-anion so that all four metals can effect Birch reductions. The few compounds for which comparative data are available are reduced in nearly identical yields by the four metals. However, lithium ion can coordinate strongly with the radical-anion, unlike sodium and potassium ions, and consequently equilibrium (3g) for lithium is shifted considerably... 

Figure 12 Effect of polymer concentration on the residual metal concentration [M] for p(AM-AANa). = Mg, O = Cu2-.

The influence of pH on the residual metal concentration [M] was studied at a constant polymer concentration of 10 mg/1 and copper sulphate concentration of 10 gm/1, results are shown in Table 4. It is clear that [M] decreases with increasing pH value. Results are given in Table 4, which shows that the concentration of Cu decreases with an increase in the pH value for each polymer used. This is attributed to the effect of the pH value on the active groups, which are distributed along the polymer chains. At a low pH value the amide groups... 

Other forms of concentration-cell corrosion include Caustic gouging Saline corrosion Combination of free caustic and concentrating effect causes severe metal wastage. High chlorides and sulfates, result in corrosion from depolarization and depassivation effects... 

The metal concentration, matrix, and temperature effects that favor clustering of the cobalt group of metal atoms have been assessed by... 

Fig. 1 Scheme illustrating the influence of water discharge (y axis) and solute concentration (metals and nutrients on the x axis) on in-stream retention efficiency measured on the basis of the nutrient spiraling concept. The most remarkable Metal (M) effects on biofihns are indicated in the... 

Table 1 Summary of metal concentrations (in )ig of total metal concentration) causing toxicity on fluvial biofilms (in terms of effective concentrations EC50) after acute exposure (of few hours of exposure) and chronic exposure (of several weeks of exposure)...

Table 2 Fate and effects of metals in a stream receiving a point-source of metals (upper part of the table) or diffuse input via urban runoff (lower part of the table). Summary of the expected influence of four different hydrological situations base-flow in a rainy period a flood after a rainy period low-flow after a long period of low rainfall (water scarcity) and a flood produced after this drought. Metal concentration (M) metal retention efficiency (measured on the basis of the nutrient spiraling concept) exposure (dose and duration) bioaccumulation (in fluvial biofilms) and metal sensitivity (of biofihns)...

Different from the metal concentration, the content of water in the reaction system exhibits an obvious effect on the particle size of the resulted metal nanoclusters. In a mixture of EG and water (10 1 in volume ratio), Pt hydroxide colloidal particles formed in the first synthesis step were 4.0 nm in average diameter, and the finally obtained Pt nanoclusters had an average particle size of... 

The alkaline EG S5mthesis method is a very effective technology for the chemical preparation of unprotected metal and alloy nanoclusters stabilized by EG and simple ions. This method is characterized by two steps involving the formation of metal hydroxide or oxide colloidal particles and the reduction of them by EG in a basic condition. The strategy of separating the core formation from reduction processes provides a valid route to overcome the obstacle in producing stable unprotected metal nanoclusters in colloidal solutions with high metal concentrations. Noble metal and alloy nanoclusters such as Pt, Rh, Ru, Os, Pt/Rh and Pt/Ru nanoclusters with small particle... 

All metals, regardless of whether they are essential or nonessential, can exhibit toxic effects at high concentrations.14-16 Excess concentrations of essential metals can lead to nonspecific binding, which can affect the enzyme structure and function. Because controlling metal concentrations is vital for maintaining homeostatic conditions within bacterial cells, evolution has bestowed upon organisms a number of ways to regulate concentrations of essential metals and to resist the toxicity of nonessential metals.17-20... 

The interpretation of previous attempts at measuring the impact of metals on microbially mediated processes has been hindered by the use of a wide range of experimental conditions and measurements. Already, a shift from studies based on total metal concentration to those based on bioavailable metal concentrations has occurred. The next step will entail accurately predicting and measuring metal speciation patterns in order to identify microbial responses to metal speciation. Only then will it be possible to develop more effective methods to quantify and mitigate deleterious effects of metals on the myriad processes that microbes mediate in the environment. 

The dc polarogram of the mixture containing the above-mentioned metal ions shows distinct steps corresponding to T1(I), Cd(II), Zn(II), and Co(II) ions only (Fig. 18) but does not provide information about the presence of the other three ions, viz., lead, indium, and nickel, in the mixture. Further, the limiting current corresponding to each step seems to be due to a combined concentration effect of lead and thallium ions, cadmium and indium ions, and zinc and nickel ions. 

Effect of Metal Concentration on Photoactivity of Titanium Dioxide... 

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