Relationship with hydroxide concentration

From the results of experiment 2.1, we confirmed decomposition reaction is pseudo first-order, and calculated pseudo first-order decomposition rate constants. Then fixnn relationship between each first-order reaction rate constant and sodium hydroxide concentration, we confirmed that the reaction is expressed by second-order with expression first-orders for both of sodium hydroxide and fenitrothion. 

In this experiment, tap water with added phosphate was used as influent. Concentration of phosphate was adjusted to an adequate range from 2 to 23 mg/jg. Calcium chloride and sodium hydroxide solution were added to maintain calcium concentration from 70 to 100 mg/jg and pH of the effluent from 9.0 to 9.5. Using this equipment, we performed experiments to obtain efficiency of phosphate removal, relationship between phosphate concentration, and crystallization rate and factors affecting phoshate removal. 

Stone et al. (S29) developed by a mathematical analysis the functional relationship between the rate of extraction of silica from pure quartz in sodium hydroxide solution and time, temperature, sodium hydroxide concentration, and particle size. With the use of response surface methodology, a comprehensive picture of this dissolution process was obtained from a few well-chosen experiments. The fractional extraction of silica can be expressed by a second-order equation. The effect of quartz particle size and temperature are predicted to be about equal and greater than the influence of sodium hydroxide concentration and reaction time. The reaction rate is controlled by the surface area of the quartz. An increase in sodium hydroxide concentration increases the activation energy for the reactions and is found to be independent of quartz size. 

Aimnonium hydroxide (NH OH) is a water solution of ammonia gas (NHp. It can also be called aqua ammonia or ammonia water. The concentration determination can be done using either a hydrometer or an acid-base titration. Since aimnonia is volatile, the concentration determination should be done with care to avoid any loss of strength. If a hydrometer is used, the sample and the hydrometer should be cooled to 5-10 °C. Table 4.7 lists the relationship between the concentration (% w/w) and "Be of NI1/ )11 at 10 °C. 

Performance of NEOSEPTA-F in Sodium Chloride Solution Electrolysis. Figure 5 shows the relationship of the cell voltage and the current efficiency respectively with the concentration of sodium hydroxide in catholyte when electrolysis of sodium chloride solution was carried out at the current density of 30 A/cm. From the economical viewpoint, i.e, the electrolysis power cost, depreciation of equipment cost, membrane cost and so on, the optimum concentration of sodium hydroxide for NEOSEPTA-F C-1000 is about 20 % and that for NEOSEPTA-F C-2000 is about 27 %. 

In the case of NEOSEPTA-F C-2000, the current efficiency increases with increase of sodium hydroxide concentration in catholyte. It is thought that the water in the membrane surface portion of cathode side is dehydrated and the concentration of fixed ion in the membrane increases. The presumption that the cathode side of the membrane surface would shrink with the increase of sodium hydroxide concentration is obviously proved in the relationship between the sodium hydroxide concentration in catholyte and sodium chloride concentration in the product ( Figure 6 ), The diffused amount of sodium chloride decreased remarkably with increase of sodium hydroxide concentration. 

When you know the relationship between the rate of a reaction and the concentration of the reactants, you can write a rate law for the reaction. Because the rate of the reaction of methyl bromide with hydroxide ion is dependent on the concentration of both reactants, the rate law for the reaction is... 

Fig. 6.7 shows the relationship between NaOH concentration and time at various NaOH initial concentrations. Ethyl acetate is initially at 0.1 moles/L for each experiment. Fig. 6.7 also displays the equations describing the relationships between NaOH concentration and time at various initial NaOH concentrations. As above, we obtain the initial reaction rates from these equations. Table 6.2 tabulates the initial reaction rates from Fig. 6.7 and their logarithms, as well as the initial NaOH concentrations and their logarithms. Fig. 6.8 shows the relationship between ln 6 [NaOH]/<7t, =o and ln[NaOH],=o- The linear correlation of the datum points in Fig. 6.8 shows the relationship of ln fi [NaOH]/<7t, =o and ln[NaOH],=o to be linear with an P of 0.9924. The slope of the correlation is 0.94, which is the order of reaction with respect to sodium hydroxide concentration. 

The resins show marked affinity relationships depending on ion size and valene. The order of affinity for common anions is S04>Cr>HC03 >F > >HSiOJ. Reaction (23) can be reversed by regenerating with moderate concentrations of sodium hydroxide solutions. However, since the reactions are not as easily reversed, regeneration levels of 150%-200% of the stoichiometric requirements are frequently employed. 

A closely related experiment attempted to determine the effect of hydroxide ion concentration on the rate of anodic processes in the absence of polarization (78). This was done with a series of Tafel plots (79) (l-V relationship near the region where the OCP) in varying hydroxide ion concentrations. The results indicated that the anodic current representative of dissolution rate in the absence of overpotential is independent of hydroxide concentration. 

The type of catalyst influences the rate and reaction mechanism. Reactions catalyzed with both monovalent and divalent metal hydroxides, KOH, NaOH, LiOH and Ba(OH)2, Ca(OH)2, and Mg(OH)2, showed that both valence and ionic radius of hydrated cations affect the formation rate and final concentrations of various reaction intermediates and products.61 For the same valence, a linear relationship was observed between the formaldehyde disappearance rate and ionic radius of hydrated cations where larger cation radii gave rise to higher rate constants. In addition, irrespective of the ionic radii, divalent cations lead to faster formaldehyde disappearance rates titan monovalent cations. For the proposed mechanism where an intermediate chelate participates in the reaction (Fig. 7.30), an increase in positive charge density in smaller cations was suggested to improve the stability of the chelate complex and, therefore, decrease the rate of the reaction. The radii and valence also affect the formation and disappearance of various hydrox-ymethylated phenolic compounds which dictate the composition of final products. 

A number of different reagent combinations were examined, along with different flowsheet combinations. The Ta/Nb-Zr separation was strongly related to the amount of Fe-hydroxide decoated. Figure 23.15 shows the relationship between Fe-hydroxide removed, Ta/Nb concentrate grade and Zr content of the Ta/Nb concentrate. 

In the 2nd period ranging from the 1930s to the 1950s, basic research on flotation was conducted widely in order to understand the principles of the flotation process. Taggart and co-workers (1930, 1945) proposed a chemical reaction hypothesis, based on which the flotation of sulphide minerals was explained by the solubility product of the metal-collector salts involved. It was plausible at that time that the floatability of copper, lead, and zinc sulphide minerals using xanthate as a collector decreased in the order of increase of the solubility product of their metal xanthate (Karkovsky, 1957). Sutherland and Wark (1955) paid attention to the fact that this model was not always consistent with the established values of the solubility products of the species involved. They believed that the interaction of thio-collectors with sulphides should be considered as adsorption and proposed a mechanism of competitive adsorption between xanthate and hydroxide ions, which explained the Barsky empirical relationship between the upper pH limit of flotation and collector concentration. Gaudin (1957) concurred with Wark s explanation of this phenomenon. Du Rietz... 

Calculating the bicarbonate concentrations with (3), it is possible to plot the measured average pH values of Table 2 against the calculated loglHCOs ]. The result is shown in Fig. 5a. For pH >5.5 a linear relationship, very close to that reported in the literature, can be observed (pH = loglHCOa ] + 11.2). However, for acid lakes the calculated bicarbonate concentrations seem to be too low. It is reported that at pH<6 the release of metals from soils or sediments as a consequence of weathering processes becomes more and more important. Consequently aluminium hydroxides can influence alkalinity. In [18] the equation for calculating alkalinity was modified as follows ... 

The rearrangements of adrenochrome (1) and adrenochrome methyl ether (8) in water and alkali are first order with respect to amino-chrome concentration.106 However, no simple kinetic relationship between the rate of rearrangement and alkali concentration was found the rate of rearrangement in the presence of sodium hydroxide increased very rapidly with increasing alkali concentration.106... 

Less attention has been paid to the reaction of cellulose with rubidium hydroxide and with cesium hydroxide. Heuser and Bartunek101 isolated adducts of rubidium hydroxide and of cesium hydroxide that had the general formula MOH 3 C Hi0Ot. Their studies showed that the concentration, in weight percent, of alkali metal hydroxide required for forming a stable adduct of the lowest alkali content increases with increase in the atomic weight of the metal Li < Na < K < Rb < Cs. However, on a molar basis, this relationship does not hold. No simple relationship exists between the size of cation and the concentration of hydroxide necessary for the formation of a stable adduct. 

Figure 16 shows relationships between the number of introduced side chains and relaxation rigidity (G,) at 900 s for carboxymethylated wood binding various metal ions [341. Wood specimens were prepared from Japanese linden Tilia japonica Smik.). Carboxymethylation and the introduction of metal ions was the same procedure as mentioned in the previous section [32,33]. Stress relaxation measurements were carried out in an aqueous solution at 30°C. The relaxational property of carboxymethylated wood without metal ions is first discussed. For carboxymethylated wood (a broken line in Fig. 16), Gf (900) decreases with an increase in the number of introduced side chain. This rapid decrease appears to be caused by two factors. One is the effect of sodium hydroxide (NaOH). Young s modulus of wood treated with an aqueous solution of NaOH decreases remarkably under wet conditions, especially at concentrations above 10% NaOH [35]. The other factor is the electrostatic repulsion of ionized carboxymethyl groups in carboxymethylated wood, as mentioned in the above section [291. For example, conformation of polypeptide is influenced by the ionization of the side chains, and the structural change of the helix-coil transition has been interpreted as a reversible transformation. Theoretical treatment of the transformation has been reported to explain the mechanism [23-25, 36-43]. The conformation of component molecules in wood, however, cannot change markedly by ionization in comparison with soluble polyelectrolytes in water, because carboxymethylated wood is not dissolved in water. Only space among the main chains is expanded by the electrostatic repulsion due to negatively charged side chains. For these reasons, G (900) of carboxymethylated wood decreases with an increase in the number of introduced side chains.

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