Ions, concentration in the

Activators enhance the adsorption of collectors, eg, Ca " in the fatty acid flotation of siUcates at high pH or Cu " in the flotation of sphalerite, ZnS, by sulfohydryl collectors. Depressants, on the other hand, have the opposite effect they hinder the flotation of certain minerals, thus improving selectivity. For example, high pH as well as high sulfide ion concentrations can hinder the flotation of sulfide minerals such as galena (PbS) in the presence of xanthates (ROCSS ). Hence, for a given fixed collector concentration there is a fixed critical pH that defines the transition between flotation and no flotation. This is the basis of the Barsky relationship which can be expressed as [X ]j[OH ] = constant, where [A ] is the xanthate ion concentration in the pulp and [Oi/ ] is the hydroxyl ion concentration indicated by the pH. Similar relationships can be written for sulfide ion, cyanide, or thiocyanate, which act as typical depressants in sulfide flotation systems. 

FIG. 22-58 Concentration profile of electrolyte across an operating ED cell. Ion passage through the membrane is much faster than in solution, so ions are enriched or depleted at the cell-solution interface, d is the concentration boundary layer. The cell gap, A should he small. The ion concentration in the membrane proper will he much higher than shown. (Couttesij Elsevier.)... 

Particle charging in a electrostatic gas-cleaning system should take place as quickly as possible. Therefore, the time constant f, should be as low as possible. This requires that the ion concentration in the charging region be high. 

The fact that the pH values of the pure metals were lower than the theoretical values was attributed to the formation of hydroxy-chloro complexes of the metal and to the high chloride ion concentration in the pit, and the results highlight the very pronounced decrease in pH that can occur in an occluded cell, particularly when the alloy contains high concentrations of chromium and molybdenum. They also showed that migration of chloride ions into the solution in the pit can result in a 7-12-fold increase in concentration, and that the potential in the pit is in the active region. 

A measured volume, 10.00 liters, of the waste process water from a cotton mill require 23.62 ml of 0.1000 M hydrochloric acid to produce a neutral solution. What is the hydroxide ion concentration in the waste ... 

Lewis and Suhr (1958b) observed the disappearance of the 4-nitrobenzenediazo-nium ion by spectrophotometry, and found that the rate increased with increasing hydroxide ion concentration in the pH range 7.5-10. At pH 10-14 and in concentrated NaOH solution the rate was independent of pH. Subsequently the rates were... 

Since the nonequilibrium concentration fluctuation arises from the dissolution of substrate metal, as shown in Fig. 43, the value of is independent of the metallic ion concentration in the bulk solution. 

The problem asks for the residual concentration of cadmium ions. In other words, what is the Cd ion concentration in the solution after the NaOH is added Before a concentration table can be completed,... 

Contemporary pH meters use single probes that contain two reference electrodes, shown diagrammatically in Figure 19-17Z). One electrode contains a buffer solution of known pH. A glass membrane separates this buffer solution from the solution whose pH is to be measured, so this electrode is called a glass electrode. Because hydronium ions participate in the cell reaction of the glass electrode, the overall cell potential depends on the hydronium ion concentration in the solution whose pH is being measured. 

The electrodeposition of tellurium and silver has been investigated in dilute aqueous solutions of tellurous acid and Ag " ions (concentrations in the order of 10 to 10 " M) in 0.1 M HCIO4 [164], In particular, cyclic voltammetry experiments were conducted with rotating glassy carbon disk electrodes in baths with various concentration ratios of Ag(I) and Te(IV) precursors, and their outcome was discussed in terms of the voltammetric features. For a Ag(I)/Te(IV) ratio close to 0.8, formation of quasi pure silver telluride, Ag2Te, was reported. The authors, based on their measurements and on account of thermodynamic predictions, assumed that silver is deposited first on the electrode (Ag" + e Ag), and then Te(IV) is reduced on the previous silver deposit with formation of Ag2Te according to the reaction... 

However, the intercepts of log [Fe(II)]/[Ce(IV)] versus time plots deviate from the values expected for the initial concentrations of the reactants. This apparent zero-time oxidation , which is reproducible, is believed to result from a finite quenching time, and the reaction of Fe(ll) with a very reactive Ce(IV) species. Added amounts of Ce(III) and Fe(lII) leave the rate unaffected. At constant ionic strength, k varies inversely with hydrogen-ion concentration in the range 0.05 to 1.00 M for [H" "] > 1.0 M, k increases with increasing In general... 

FIG. 6 Dependence of the square root of the SHG intensity ( I(2a>)) for membrane 2 without KTpCIPB (a) with KTpCIPB (b) on K+ ion concentrations in the adjacent aqueous solution containing KCl (O) and KSCN ( ), respectively. Inset The corresponding observed EMF to KCl and KSCN. The concentrations of ionophore 2 and KTpCIPB were 3.0 X 10 M and 1.0 x 10 M, respectively for both SHG and EMF measurements. The data points present averages for three sets of measurements. Error bars show standard deviations. (From Ref. 15.)... 

In the practice of potentiometric titration there are two aspects to be dealt with first the shape of the titration curve, i.e., its qualitative aspect, and second the titration end-point, i.e., its quantitative aspect. In relation to these aspects, an answer should also be given to the questions of analogy and/or mutual differences between the potentiometric curves of the acid-base, precipitation, complex-formation and redox reactions during titration. Excellent guidance is given by the Nernst equation, while the acid-base titration may serve as a basic model. Further, for convenience we start from the following fairly approximate assumptions (1) as titrations usually take place in dilute (0.1 M) solutions we use ion concentrations in the Nernst equation, etc., instead of ion activities and (2) during titration the volume of the reaction solution is considered to remain constant. 

In order to obtain the ion concentrations in the pure solvent, we can consider the equilibrium constant K w of the overall reaction 4.3, as separation step 4.1 is followed almost instantaneously by solvation step 4.2, and so... 

At present it is impossible to formulate an exact theory of the structure of the electrical double layer, even in the simple case where no specific adsorption occurs. This is partly because of the lack of experimental data (e.g. on the permittivity in electric fields of up to 109 V m"1) and partly because even the largest computers are incapable of carrying out such a task. The analysis of a system where an electrically charged metal in which the positions of the ions in the lattice are known (the situation is more complicated with liquid metals) is in contact with an electrolyte solution should include the effect of the electrical field on the permittivity of the solvent, its structure and electrolyte ion concentrations in the vicinity of the interface, and, at the same time, the effect of varying ion concentrations on the structure and the permittivity of the solvent. Because of the unsolved difficulties in the solution of this problem, simplifying models must be employed the electrical double layer is divided into three regions that interact only electrostatically, i.e. the electrode itself, the compact layer and the diffuse layer. 

Conversely, a decrease in the arterial PCOz due to hyperventilation results in a decrease in the H+ ion concentration in the ECF of the brain. Decreased stimulation of the central chemoreceptors (and therefore a decrease in the excitatory input to the medullary respiratory center) causes... 

Calculate the approximate acetic acid concentration and acetate ion concentration in the final solution after 50.0mL of 0.200 M HC2H302 is treated with 50.0 mL of 0.100 M NaOH. 

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