Ions In Acidic Solution Research Articles

Modified normal pulse polarography of barium(II) in acid solutions.

A new method of normal pulse polarography is presented in which the current is sampled after the end of each pulse. This current is plotted against the potential of the pulse, which is changed gradually. An instrument for this purpose is constructed. The advantage of the method is demonstrated by the determination of barium(II) ions in acid solutions. The anodic stripping current at -1.0 V vs. SCE of barium amalgam formed on a dropping mercury electrode during a period of pulse was proportional to the concentration of barium(II) and was not affected by the presence of 0.01 mol dm-3 hydrochloric acid.

Spectrophotometric determination of sulfite with soluble mercury(II) compounds

Sulfite ion reacts with mercury(II) ion in acid solution to form the mercury(I) ion. The reaction is rapid and quantitative. The mercury(I) ion absorbs at 237 nm with a molar 5 Beer's law Data for Sulfite Complexes of Covalent Mercury(II) Compounds SO 2 (ppm) ϵHgCl 2 a ϵHgBr 2 ϵHg(Ac) 2 b ϵHg(SCN) 2 2.0 12,500 10,000 10,000 9,200 4.0 12,500 11,500 10,000 9,000 6.0 12,500 11,500 10,000 9,200 8.0 12,000 11,000 10,500 9,800 a Molar absorptivity based on sulfite ion at 230 nm. Solution was 6.86 buffer. b Mercuric acetate solutions seemed to be somewhat unstable. absorptivity of about 25,000. The absorbance is linear over a range of approximately 0.5–5.0 ppm as SO 2. Covalent mercury(II) compounds form a complex with sulfite, Hg(SO 3) 2 2−, which absorbs at 230 nm and shows a linear response over a range of 1–8 ppm as SO 2.

New trinuclear aquo ions of molybdenum

. . . . We wish to report experiments in which reversible electrolytic reduction of the aquo Mo(IV)s ion in acidic solutions yields first the orange-pink Mo(II1, III,IV), and then the green Mo(III)a aquo ion. The latter is also obtained by reduction of Mo(IV), with Zn/Hg. . . ‘,., . . . 300 7M)

The partitioning of tetrahedral intermediates of the hydrolysis of benzimidatonium ions in acid solutions

The products (a benzoate ester or an N,N-dimethylbenzamide) have been accurately determined for the hydrolysis of the O-ethyl-N,N-dimethylbenzimidatonium ion (1) and its 4-nitro derivative (2) in dilute and moderately concentrated H2SO4 solutions. In dilute acid the ratio of amide:ester is very small (0.0005–0.001). It is proposed that the ester product arises from the zwitterionic form of the tetrahedral intermediate of the hydrolysis. The small amount of amide is due to an SN2 hydrolysis reaction and to the non-catalyzed breakdown of the neutral form of the tetrahedral intermediate, the relative contributions of the two being unknown. Although ester remains the major product throughout, at some intermediate acid concentration (20% H2SO4 for 1 and 35% H2SO4 for 2) a sharp increase in the amide:ester ratio is observed, followed by a levelling-off. This change is shown to be associated with tetrahedral intermediate partitioning, and not the SN2 reaction. It is argued that the strong acid product ratio represents the breakdown of the tetrahedral intermediate via cationic transition States. Two kinetically equivalent reactions are involved, the breakdown of the N-protonated tetrahedral intermediate producing a protonated ester and amine and the H+-catalyzed breakdown of the neutral tetrahedral intermediate producing a protonated amide and alcohol. Analogous pathways are also observed for the decomposition in acid of the amide acetals ArC(OMe)2NMe2, and the two systems are compared. A similar effect of the aromatic substituent on the partitioning ratio is noted, but the tetrahedral intermediate exhibits a greater tendency for amine expulsion. A kinetic analysis produces the estimate of 1011 s−1 for the rate constant for the breakdown of the zwitterionic form of the tetrahedral intermediate. This very large rate explains why its decomposition remains important even in concentrated acids, where the amount of tetrahedral intermediate which actually exists as zwitterion must be extremely low.

Studies on the Preparation of Cuprous Oxide. VIII. A Spectrophotometric Study of Halogenocopper(I) Complexes in Aqueous 5 M Na(ClO4) Solutions

Abstract The complex formation of copper(I) with bromide and iodide ions in aqueous 5 M (1 M=1 mol dm−3) Na(ClO4) solutions was studied spectrophotometrically over a pH range from acidic to alkaline. Over the concentration range of 0.05–5 M bromide ions in acidic solutions, the CuBr2− and CuBr32− complexes were found. On the other hand, in the iodide system the CuI2−, CuI32− complexes and a higher complex were found under the same experimental conditions, although the composition and the formation constant of the last complex could not be determined in this study. The equilibrium constants for the reactions, CuX2−+X−=CuX32−, were 13 and 1.6 for the bromide and iodide complexes respectively. A hydrolyzed species of copper(I), Cu(OH)2−, was found in an alkaline solution of the two systems. The formation constants, β−22=[Cu(OH)2−][X−]2⁄[CuX2−][OH−]2, were evaluated as follows: β−22=(10.0±0.7)×107([Br−]<2M),(2.6±0.7)×107([Br−]=3M),(1.7±0.7)×107([Br−]=4M) in the bromide solutions, (4.0±0.4)×103 ([I−]<2 M), (2.5±0.4)×103 ([I−]=3 M), (2.2±0.4)×103 ([I−]=4 M) in the iodide solutions.

Electrophilic substitution in pyrroles. Part 5. Reaction of dipyrrylmethanes with arenediazonium ions

Dipyrrylmethanes react with arenediazonium ions in acid solution to form azopyrroles and formaldehyde. At low pH cleavage of the methylene bridge is brought about by attack of hydrogen ions, but at higher pH arenediazonium ions assume this role. In the reaction of benzylpyrrole, benzyl alcohol was detected as a product, suggesting formation of a benzyl carbonium ion. The relevance of these studies to the van den Bergh test for bilirubin is considered.

Dioxouranium (VI) carbonate complexes in acid solution

The equilibria of dioxouranium (VI) and carbonate ions in acid solution (log [H +] > −5) have been studied at 25°C by measuring, with a glass electrode, the hydrogen ion concentration of a series of UO 2− 2+ perchlorate solutions, saturated with CO 2(g) at known partial pressure. The investigation covers the [U(VI)] values from 2.5 × 10 −4 to 0.01 M, and the partial pressure of carbon dioxide from 0.2 to 0.97 atm. For each [U(VI)] level the hydrogen ion concentration was decreased from a value, corresponding to negligible complex formation, until solid U(VI) carbonates start to form. All the solutions contained 3 MClO 4 added as NaClO 4. The e.m.f. data may be explained by assuming, in addition to the hydrolysis complexes[24], the formation of UO 2(OH) 2CO 2(=UO 2CO 3), (UO 2) 3(OH) 5CO 2 +(=(UO 2) 3(OH) 3CO 3 +) and a large species of probable composition (UO 2) 11(OH) 24(CO 2) 6 2−, with the equilibrium constants given in Table 3.

Photooxidation of dichloro- and trichlorocuprate(I) ions in acid solution

Die durch UV-Licht induzierte Oxidation der in HCl-haltiger CuCl-Losung anwesenden Spezies CuCl2- (absorbiert bei 230 und 273 nm) und CuCl32- (absorbiert bei 273 nm) zu CuCl+ (und anderen Cu(II)-Spezies) und H2 wird untersucht.

Equilibria in complexes of N-heterocyclic molecules. XVII. Covalent hydration and the rate of dissociation of the Bis(2,2':6',2'-terpyridyl)iron(III) ion in acid solution

The dissociation of Fe(tpy)23+ has been studied in aqueous sulfuric acid. The rate of reaction increases upon addition of small amounts of acid, reaches a maximum, and then falls to zero in a complex fashion as the acid approaches limiting concentration, and aH2O falls to zero. No dissociation occurs in the absence of water, and it is evident that covalent hydration of the complex is an essential step in the dissociation process.

THERMODYNAMIC CONSIDERATIONS ON THE SOLUBILITY OF PHOSPHATE ROCK

ABSTRACTTheoretical considerations from the free energy concept on the solubility of phosphate rock indicate that the free energy of neutralization of anions in apatite with the hydrogen ions in acid solution decreases linearly with the carbonate substitution in carbonate apatite and the hydroxyl su

Interaction of Fe(III)- and polymeric Zr(IV)-ions in acid solutions

Interaction of Fe(III)- and polymeric Zr(IV)-ions in acid solutions

Electrophilic substitution in pyrroles. Part 2. Reaction with diazonium ions in acid solution

The kinetics of the reactions of five substituted benzenediazonium ions with up to eleven different pyrroles have been examined in detail by stopped-flow spectrophotometry. All the evidence favours attack of the unprotonated pyrrole in an SE2 mechanism, with a steady-state intermediate. A consideration of two linear free-energy relationships shows that little can be deduced about the nature of any transition state in these reactions. However, protonated pyrrole is a good model for the steady-state intermediate. The activating effects of a methyl group towards electrophilic attack at various positions on the ring have been calculated. The special reactions of 3,4-dimethyl- and 2,3,4,5-tetra-methyl-pyrrole are discussed.

Reactivity of xanthate and dixanthogen in aqueous solutions of different pH

In contrast to the high reaction rates of xanthate ions in acidic solutions (established byIwasaki andCooke) the decomposition of ethyl xanthate ion (O-ethyl dithiocarbonate ion) in alkaline pH (7–12) is independent of pH; a first order rate constant with respect to xanthate ion is obtained equal to 2.1 ± 0.3 × 10−7 liter mole−1 sec−1. Reaction products are found to be the same as in decomposition of xanthate by acids, i. e. CS2, ethyl alcohol and OH−, but even in the presence of dissolved oxygen no dixanthogen is formed in a homogeneous system unless a catalyst is available. Ethyl dixanthogen, formed catalytically or by an oxidizing agent more powerful than dissolved oxygen (e. g. Cu++, I2, etc.) has a constant solubility in acid solutions — 1.25 × 10−5M (in pH 2.8–8.4). The decomposition of ethyl dixanthogen in alkaline pH is a two-step process; it involves a nucleophilic displacement reaction by OH− viz. 1 $$\left( {EtX} \right)_2 + OH^ - \to EtXOH + EtX^ - $$ and base-hydrolysis of the intermediate product EtXOH viz. 1 $$EtXOH\xrightarrow{{H_2 O}}EtOH + CS_2 + OH^ - $$ where EtX− represents ethyl xanthate and (EtX)2 diethyl dixanthogen). The rate of the overall reaction is first order with respect to each of the reactants dixanthogen and OH−. The experimental rate constantk 2 was calculated to bek2=0.24±0.005 liter mole−1 sec−1. On the basis of additional semiquantitative tests an order of reactivity of dixanthogen with other nucleophilic substituents is proposed; $${\text{HS}}^ - > {\text{CN}}^ - > {\text{OH}}^ - > {\text{SO}}_{\text{3}}^{\text{ = }} > {\text{S}}_{\text{2}} {\text{O}}_{\text{3}}^{\text{ = }} > {\text{EtX}}^ - > {\text{SCN}}^ - > {\text{I}}^ - $$

The kinetics of the step-wise aquation of the oxalatobis(ethylenediamine) chromium(III) ion in acid solution

Abstract Four stages in the aquation of the Cr en2ox+ ion have been studied in the hydrogen ion concentration range 1·0-0·1 M The stages followed with the corresponding rate constants, × 107/sec−1, 298 K, H+ = 1·0 M, and activation parameters, ΔH ‡ / cal. K −1 mole −1 are ase as follows: Cr en2ox+ → Cr en(enH)ox(H)2O)2+, 190 ± 5, 19·7 ± 0·4, −14 ± 1; Cr en(enH)ox(H2O)2+ → Cr en ox(H2O)2+, 184 ± 8, 20·1 ± 1·0, −13 ± 1; Cr en ox(H2O)2+ → Cr(enH)ox(H2O)32+, 63 ± 3, 19·5 ± 0·3, −17 ± 1; Cr(enH)ox(H2O)32+ → Cr ox(H2O)4+, 25 ± 1, 22·1 ± 0·1, −10 ± 1. ∗ Mathematical analysis of the overall absorbance changes suggests that isomerization reactions are involved in the aquation of the Cr en2ox+ ion. A comparison is made of kinetic data now known for a number of complexes which show labilization of chromium-nitrogen bonds.

A study on chloride ion dissociation in K 3[Ru 2NCl 8(H 2O) 2

μ-Nitrido-bis[aquatetrachlororuthenate(IV)] ion, [Ru 2NCl 8(H 2O) 2] 3−, liberates three chloride ions in acid solution during the first 4 hours after dissolution. Change in the absorbance of the solution was followed at two wavelengths, and three rate constants were determined using the curve-fitting method. These constants were also estimated by determining the amount of chloride ion liberated. From the results first-order reactions in three successive steps liberating chloride ion were proposed. The three rate constants were 0·010 min −1 (first step), 0·025 min −1 (second step) and 0·009 min −1 (third step).

The effect of proteins on the electrode reaction of metal ions at the mercury electrode

The inhibiting effect of the proteins gelatine, albumine and histone on the polarographic reduction of several metal ions in acidic solutions has been discussed. It has been found that the differences in the double layer capacity at a mercury electrode in neutral and acidic solutions containing proteins cannot account for the substantial influence of pH on the inhibiting effect. It is suggested that the extremely low transfer coefficient for the inhibited cation reduction processes is due to the position of the energy barrier at a distance from the electrode comparable with the radius of a positively charged protein molecule.

The effect of proteins on the electrode reaction of metal ions at the mercury electrode

Summary The inhibiting effect of the proteins gelatine, albumine and histone on the polarographic reduction of several metal ions in acidic solutions has been discussed. It has been found that the differences in the double layer capacity at a mercury electrode in neutral and acidic solutions containing proteins cannot account for the substantial influence of pH on the inhibiting effect. It is suggested that the extremely low transfer coefficient for the inhibited cation reduction processes is due to the position of the energy barrier at a distance from the electrode comparable with the radius of a positively charged protein molecule.

On the complex formation between lead(II) and citrate ions in acid solution

Complex formation between lead(II) and citrate ions ( L) has been investigated potentiometrically at 25°C and in 2 M Na(ClO 4) by using a lead amalgam electrode and a glass electrode. The experimental data can be explained by assuming the following equilibria: Pb 2++ L→ PbL log β 1, 0, 1= 4·08±0·10 Pb 2++H ++ L→ PbHL log β 1, 1, 1= 8·15±0·05 Pb 2++2H ++ L→ PbH 2L log β 1, 2, 1=10·85±0·10 Pb 2++2 L→ PbL 2 log β 1, 0, 2=6·06±0·20 Pb 2++2H ++2 L→ PbH 2L 2 log β 1, 2, 2=14·95±0·15 Pb 2++4H ++2 L→ PbH 4L 2 log β 1, 4, 2=21·68±0·15 Symbols: L = citrate ion = C 6H 5O 7 3− B = total concentration of Pb 2+ b = free concentration of Pb 2+ A = total concentration of citrate ions a = free concentration of citrate ions H = total concentration of hydrogen ions h = free concentration of hydrogen ions K n = formation constants of citric acid, defined as follows: K n = [H nL] h[H n−1L] where n=1,2,3 β q, p, r = stability constants of a species Pb q H p L r , defined as follows: β q,p,r = [Pb qH pLr] b qh pa r Charges are generally omitted.

Titrimetric determination of ionic and coordinated azide ion by oxidation with excess nitrite ion in acid solution

Titrimetric determination of ionic and coordinated azide ion by oxidation with excess nitrite ion in acid solution

The anodic oxidation of boronic acids—III. Methaneboronic acid

The anodic oxidation of methaneboronate ions in alkaline solution produces ethane and methanol. In concentrated solutions, ethane is the predominant product; the yield of ethane approaches that obtained by oxidation of acetate ion in acid solution.