Free Chloride Ions Research Articles

Pore solution chemistry and corrosion in hydrated cement systems containing chloride salts: a study of cation specific effects

The free chloride and hydroxyl ion concentrations of the pore electrolyte phase present in mature, hydrated cement pastes containing equivalent quantities of chloride ion, introduced into the mix water as NaCl or CaCl2, have been determined for two commercial cements. The corrosion rates of mild steel electrodes embedded in these materials have also been monitored by the method of linear polarization. It has been found that specimens containing CaCl2 are more aggressive than those with NaCl for the range of concentrations examined, but the effect appears to be a result of changes occurring in the early stages of hydration, rather than of longer term modifications in the pore solution chemistry.

A pulse radiolysis study of tetraammineplatinum(II) complex ion in aqueous chloride media

The reaction of dichloride anion radical with tetraammineplatinum(II) ion has been studied in aqueous, acidic solution using the fast-reaction technique of pulse radiolysis in conjunction with UV-visible absorption detection. The second-order rate constant for the reaction of Cl . 2 radical with the platinum(II) complex is calculated to be (9±1) × 10 9 dm 3·mol -1·s -1, and the reaction leads to products which absorb strongly in the region of 250–350 nm. Very similar spectral features arise from the reaction of hydroxyl radical and Pt(NH 3) 2+ 4 in the presence of low concentrations of free chloride ion. The transients are proposed to be platinum(III) chloro species, and the interrelationships between the species are discussed.

Electrochemical Studies of Tetrabutylammonium Electrolytes at Carbon Cathodes in Sulfuryl Chloride Cells

Tetrabutylammonium tetrachloroaluminate has been explored for use as a soluble conducting electrolyte in sulfuryl chloride cells. Cathode capacity and voltage characteristics in this electrolyte are compared to those obtained when using electrolyte. Cathode life in is more than 50 times greater than that found in due to formation of soluble reaction products. Lowered carbon rest potentials in electrolytes are due to the presence of free chloride ions.

Electrochemical monitoring of corrosion of steel in microsilica cement pastes

The corrosion behaviour of steel in hardened cement pastes containing various proportions of microsilica and sodium chloride has been studied by corrosion potential and linear polarisation measurements. Replacement of increasing proportions of Portland cement with microsilica in pastes of constant total chloride content and water content caused the ratio of free chloride ion concentration to hydroxyl ion concentration in the pore water to increase. This tended to destabilise the passivity of steel during the early stages of hydration but the effect became less significant as curing progressed. It is suggested that the growth of anodic pits may be restrained in microsilica cement pastes owing to the fine pore structure of the material which limits the mobility of chloride ions near the surface of embedded steel.

REINFORCEMENT CORROSION AND THE DURABILITY OF CONCRETE BRIDGES.

Keywords TRANSPORT AND ROAD RESEARCH LABORATORY, TRRL REINFORCEMENT, CORROSION, DURABILITY, CONCRETE, BRIDGES, SUBSTRUCTURES, SUPERSTRUCTURES, DEICING, SALT, METHODS, PREVENTION, DETECTION, DECKS, LOCALISED, CARBONATION, CHLORIDE, PROBLEMS, DATA, ALTERNATIVE, SITE INVESTIGATION, TESTS, REPAIRS, ANODES, DAMAGE, CATHODIC, CHEMICAL, CHEMISTRY, PHYSICAL, EFFECT, STEEL, CARBON DIOXIDE, COVERS, CONTAMINATION, SURFACES UK... Show All

Electric properties of negative ions: Dipole polarizability of the chloride ion

The polarizability of the chloride ion is computed using the coupled Hartree-Fock method and fourth-order manybody perturbation theory. The coupled Hartree-Fock result is 31.5 au. The fourth-order correlated results lead to a total polarizability for the free chloride ion of 37.5 au (5.6 A 3). A revision of empirical estimates is recommended.

The enrichment of hydrogen and chloride ions in the crevice corrosion of steels

The changes in concentration of hydrogen and chloride ions during corrosion in an artificial crevice on steel were observed from potential changes of Pd-H and Ag/AgCl micro-electrodes inserted in the crevice. Increasing the bulk chloride ion concentration accelerated the rate of pH change and resulted in more acidic conditions in the crevice. Such pH changes were delayed by the addition of inhibitor such as dialkylamines. Though the free chloride ion concentration did not change appreciably, the total concentration of free and complex ions in the crevice increased with continuous dissolution of the steel. Increasing the hydrogen and total chloride ion concentration in the crevice accelerated the anodic dissolution of steels within the crevice.

Formation and characterization of platinum(III)-ethylenediamine complex ions using pulse radiolysis

Pulse radiolysis experiments using conductivity, polarographic and uv-visible absorption detection techniques have been carried out on the reaction of hydroxyl radical with bis(ethylenediamine)platinum(II)perchlorate in aqueous media. This reaction is shown to proceed by OH addition to the platinum center to yield a nascent product where the metal is in a formal oxidation state of III. The subsequent behavior of this Pt(III) transient generates three additional transients, whose formations are dependent upon the pH and presence of free chloride ion. A mechanism is proposed whereby these transients are interrelated through acid-base, chloride substitution, and water elimination processes. Evidence is presented to support the classification of the Pt(III) species into two groups having the compositions of Pt(en)/sub 2/(X)/sup n+/ (X = OH, H/sub 2/O, Cl; n = 2,3) and Pt(en)(en-H)/sup 2 +/ (en-H = /sup -/NHCH/sub 2/CH/sub 2/NH/sub 2/). For the former group, the respective wavelength maxima and molar absorption coefficients are 270 nm, ca. 4500 M/sup -1/ cm/sup -1/ (X = OH), < 250 nm (X = H/sub 2/O), and 260 nm, 8000 M/sup -1/ cm/sup -1/ (X = Cl). For Pt(en)(en-H)/sup 2 +/, two absorption bands are found with peaks at 340 nm (2900 M/sup -1/ cm/sup -1/) and 480more » nm (1500 M/sup -1/ cm/sup -1/). This latter species is also the major product of the reaction of the hydrated electron and trans-di-hydroxobis(ethylenediamine) platinum(IV) perchlorate which was investigated by absorption and conductivity techniques. The possible structures of these intermediates are discussed.« less

X-ray diffraction study of ferric chloride solutions and hydrated melt. Analysis of the iron (III)–chloride complexes formation

A series of concentrated ferric chloride solutions, both neutral and acidic, as well as the hydrated melt FeCl3⋅6H2O have been studied by x-ray diffraction. The changes in the radial distribution curves by varying iron concentration or Cl−/Fe3+ ratio and least squares fitting of the structure functions for various solute models lead to an unambiguous conclusion with respect to the dominant species which are present in the solutions. The existence of monochloro, dichloro, trichloro, and tetrachloro complexes, predicted by literature information in dilute solutions, has been established in the different solutions investigated. Octahedral complexes, mainly Fe(H2O)4Cl+2 and Fe(H2O)3Cl3, are the principal species occurring in neutral and acidic solutions while in the hydrated melt tetrahedral FeCl−4 predominates. Species of the type FeCl5(H2O)2− or FeCl3−6 as well as polymeric network are excluded. Hydration water molecules around Cl− anions has been found for both free chloride and chloride ions bonded to iron atoms. Second order interactions around Fe3+ ions are strongly suggested by the presence of a large peak at about 4.2 Å in the distribution curves.

Kinetic studies on the interaction of gold(III) with nucleic acids. I. Native DNA-Au(III) system-spectrophotometric studies

Kinetics of the interaction of Au(III) with native calf thymus DNA has been studied spectrophotometrically to determine the kinetic parameters and to examine their dependency on the concentrations of DNA and Au(III), temperature, ionic strength and pH. The reaction is of the first order with respect to both the nucleotide unit of DNA and Au(III) in the stoichiometry of 2∶1 respectively. The rate constants vary with the initial ratio of DNA to Au(III) and is attributed to the effect of free chloride ions and the existence of a number of reaction sites with slight difference in the rate constants. The activation energies of this interaction have been found to be 14–16 kcal/mol. From the effect of ionic strength the reaction is found to occur between a positive and a negative ion in the rate-limiting step. The logarithm of rate constants are the linear function of pH and the slopes are dependent on ther-values. A plausible mechanism has been proposed which involves a primary dissociation of the major existing species (AuCl2(OH)2)−, to give (AuCl2)+ which then reacts with a site in the nucleotide unit of DNA in the rate-liminting step followed by a rapid binding to another site on the complementary strand of the DNA double helix. There exist a number of binding sites with slight difference in reactivity.

Active site of ribonucleoside diphosphate reductase from Escherichia coli. Inactivation of the enzyme by 2'-substituted ribonucleoside diphosphates.

Ribonucleoside diphosphate reductase is an allosteric enzyme consisting of two nonidentical subunits, proteins B1 and B2. B1 contains dithiols which participate in the oxidation-reduction reactions of electron transport, while B2 contains a free radical essential for activity. Ribonucleoside diphosphates are bound to B1 but not to B2. Addition of 2'-deoxy-2'-chloro ribonucleoside diphosphates to ribonucleotide reductase irreversibly inactivates B1 without affecting B2. The reaction is specific since (a) it requires the presence of active B2, (b) it is controlled by allosteric effectors, (c) B1 is protected against inactivation by the normal substrates, and (d) the chloro-substituted nucleoside monophosphates have no effect. The inactivation of B1 is caused by a modification of the oxidation-reduction dithiols. The chloro derivatives decompose into free base, chloride ion, and 2-deoxyribose 5-diphosphate as a consequence of reaction with the enzyme. 2'-Deoxy-2"-azido ribonucleoside diphosphates cause an irreversible inactivation of B2 without affecting B1. The reaction is specific by the above criteria, indicating that the azido derivatives also bind to the active site of the enzyme. On reduction by ribonucleotide reductase, the azido derivatives function as radical scavengers and selectively destroy the free radical of B2, indicating that this radical participates in ribonucleotide reduction directly. On the basis of these results, a model of the active site of ribonucleotide reductase is proposed in which the site is formed from both B1 and B2. In the site the electron-donating oxidation-reduction active dithiols of B1 are in close contact with the free radical of B2. The azido derivative also inactivates the adenosylcobalamin-dependent ribonucleoside triphosphate reductase from Lactobacillus leichmannii and a ribonucleotide reductase preparation from calf thymus, indicating a general involvement of free radical intermediates in enzyme-catalyzed ribonucleotide reduction.

A pulse radiolysis and flash photolysis study of the formation and characterization of platinum (III) amine complex ions

An investigation into the formation and characterization of the transients arising from the reactions of hydroxyl radical with the complexes bis(ethylenediamine)platinum(II) perchlorate and chloride, chloro(diethylenetriamine)platinum(II) chloride and chloro(1,1,7,7-tetraethyldiethylenetriamine)platinum(II) chloride in aqueous media saturated with nitrous oxide has been carried out using the technique of pulse radiolysis. In general, the transients exhibit absorption bands with either a single, intense peak below 300 nm (ϵ ⪞ 400 m 2 mol −1) or for the longer-lived species, two peaks of lesser intensity at about 350 and 500 nm. For the bis(ethylenediamine)-platinum(II) system, the transients are interrelated by acid-base reactions and in the presence of free chloride ion by substitution process. The disappearance of the longer-lived intermediate, which obeys second-order kinetics, does not lead to the formation of detectable amounts of ammonia (or free ethylenediamine). This feature in conjunction with other results indicates that the transients are not those arising from the degradation or loss of the co-ordinated amine ligand. Some of the intermediates exhibit reactivity towards either copper(II) perchlorate, an oxidant, or the reducing agent potassium ferrocyanide. The flash photolysis of trans-dichlorobis(ethylenediamine)platinum(IV) perchlorate has been used to generate and further characterize some of the transients encountered in the pulse radiolysis study. It is concluded that the intermediates are platinum(III) amine complex ions. For the Pt(III) species with absorption peaks below 300 nm, their structures are proposed to be distorted octahedra with substitutionally labile co-ordination sites. It is suggested that the products absorbing above 300 nm may be structurally different from those absorbing below 300 nm.

Reactions between tetrachlorogold(III) ions and N-cyclohexylthiobenzamide

Kinetic and spectroscopic evidence is presented which shows that in aqueous solution tetrachlorogold(III) ions and N-cyclohexylthiobenzamide (S) interact stoicheiometrically to form the 1 : 1 complexes [AuCl2(OH)(S)]0, [AuCl2(H2O)(S)]+, [AuCl3(S)]0, and [AuCl5(S)]2–. The complexes are in rapid equilibrium and their relative concentrations depend upon the free chloride and hydrogen ion concentrations. All the complexes decompose, probably via a slow reaction with water, to give the O-amide and gold sulphide. In this decompostion [AuCl5(S)]2– is the most reactive and the addition of chloride ions to a reaction mixture can therefore provide catalysis based on the conversion of a four- to a six-co-ordinated species. A possible explanation is given.

The Reaction of Chlorite with Horseradish Peroxidase and Chloroperoxidase: ENZYMATIC CHLORINATION AND SPECTRAL INTERMEDIATES

Chloroperoxidase and horseradish peroxidase use NaClO2 as both the oxidant and the halogen donor for the peroxidative chlorination of monochlorodimedone. Previous studies have shown that both horseradish peroxidase and chloroperoxidase can catalyze iodination reactions with hydrogen peroxide as the oxidant; however, only chloroperoxidase catalyzes chlorination reactions under these conditions. The chlorite chlorination reactions obey normal Michaelis-Menten kinetics with respect to chlorite. Free chloride ion is not required for the chlorite-promoted chlorination reaction and has no effect on the Km values for chlorite or the Vmax values for either enzyme. The Vmax for the chlorination of monochlorodimedone by chloroperoxidase when chlorite is the substrate is approximately 3 times greater than when hydrogen peroxide is the oxidant, suggesting that chlorite is an exceptionally good substrate. The pH optimum for the chlorination reaction with horseradish peroxidase as catalyst is 4.1 and with chloroperoxidase a broad optimum from pH 2.25 to 3.0 is observed. Chloroperoxidase can also utilize chlorite as the oxidant for the oxidation of classical peroxidase substrates such as guaiacol, pyrogallol, and thiourea. Horseradish peroxidase reacts with chlorite to form a relatively stable product (half-life greater than 20 min) which is spectrally indistinguishable from Compound I, the first detectable intermediate formed upon the reaction of horseradish peroxidase with peroxides. The reaction yielding the horseradish peroxidase-Compound I spectrum has a precise stoichiometry. The addition of increments of chlorite to horseradish peroxidase results in the generation of a family of spectra exhibiting sharp isosbestic points at 420, 450, and 540 nm. One mole of chlorite converts 2 moles of horseradish peroxidase to the intermediate product or products having the Compound I spectrum. The addition of reducing agents such as potassium ferrocyanide to the Compound I-type intermediate results in the rapid decomposition of the intermediate and regeneration of the spectrum of the native enzyme. Incorporation studies using 36Cl indicate that the chlorine atom derived from chlorite is incorporated directly into the substrate acceptor molecule during chlorination and does not undergo exchange with free chloride ion, even in the presence of exceedingly high levels of free halide. This suggests that the reaction of chlorite with both horseradish peroxidase and chloroperoxidase results in the formation of an enzyme-bound activated halogenating intermediate. These results, in conjunction with our previous studies on the chemical nature of Compound I, suggest that the activated halogenating intermediate may be represented as an enzyme-bound halogenium ion (—X+) or hypohalite ion (—OX+) coordinated to the heme prosthetic group.

Kinetics and mechanism of the reaction between N‐and N,N′‐methyl ethylenediamines and palladium(II) chloro complexes in aqueous acid medium

AbstractThe substitution of N‐alkyl substituted ethylenediamines for chloride ions in the rapidly equilibrating system has been investigated in aqueous acid medium. The kinetic data can be accommodated by the general rate law where n = 0, 1, or 2 and m = 0, 1, or 2, depending on whether none, one, or two methyl groups are attached to the two nitrogen atoms of ethylenediamine. Reaction with the most heavily substituted ethylenediamine, namely, N2N2en discloses a change of the mentioned rate law to on going from a lower to a higher chloride ion concentration range. This change in the mathematical form of the rate law can be explained in terms of an ion‐pair association of N2N2enH+ and free chloride ions.

Kinetic studies on the interconversion of mer-trichloro(o-dimethylaminophenyldimethylarsine-As)(o-dimethylaminophenyldimethylarsine-NAs)rhodium(III) and trans-dichlorobis(o-dimethylaminophenyldimethylarsine-NAs)rhodium(III) chloride

The kinetics of the interconversion (i) have been studied in hydroxylic solvents (L and L′=o-dimethylamino-mer-[Rh(L)(L′)Cl3]⇌trans-[Rh(L)2Cl2]++ Cl–(i) phenyldimethylarsine-NAs and -As respectively). The rate of the forward reaction depends on the concentration of electrolytes in solution (NaClO4, NEt4ClO4, or LiNO3), according to the rate law, rate =(k(m→t)1+k(m→t)2[Salt])[mer-Rh(nas)2Cl3], and increases sharply with the polarity of the solvents. A dissociative mechanism involving extensive Rh–Cl bond rupture in the activated complex is proposed. Such a mechanism is supported by the activation parameters. The rate of the reverse reaction shows a linear dependence on LiCl when the total amount of lithium salts is kept constant by addition of LiNO3, while a square-root dependence on LiCl is observed in the absence of added LiNO3. An SN1 (IP) mechanism is proposed for this reaction, involving a precursor ion-pair of the trans-complex with a free chloride ion. A very small solvent effect is observed in this case and is interpreted as the consequence of opposing effects of the polarity of the solvent both on the dissociation of LiCl and on the formation constant of the precursor ion-pair.

Photochemistry of π-cyclopentadienylcarbonylmetal halides in dimethyl sulphoxide and related solvents

The principal product when solutions in dimethyl sulphoxide or pyridine of π-cyclopentadienylcarbonylmetal halides of Fe, Mo, and W are irradiated at long wavelengths (λ > 400 nm) is a dimer: this is [(π-C5H5)Fe(CO)2]2 in the case of Fe (indicating loss of halogen) but appears to be [(π-C5H5)M(CO)2Cl]2 for Mo and W; free cyclo-pentadiene and chloride ion are also produced in the case of Fe. The reactions do not proceed in non-polar solvents. At shorter wavelengths (λ > 280 nm) the principal product in all cases is a dimeric species which could not be isolated, but which spectral data suggest to correspond to displacement of one CO molecule by solvent from the dimers obtained at longer wavelengths; moreover i.r. and n.m.r. spectral profiles of the λ > 280 nm reaction indicate that the latter are essential intermediates in all three cases.

Tissue reactions to 2-chloroethanol in rabbits

2-Chloroethanol is a potential reaction product between ethylene oxide and a free chloride ion. Certain plastic devices, such as those of the polyvinyl chloride types, contain such free chloride ions and are often sterilized by ethylene oxide. Depending on the chloride ion content and residual ethylene oxide, varying amounts of 2-chloroethanol (a chlorohydrin) may be formed as the reaction product. Since this agent is less volatile than the ethylene oxide, standard degassing procedures may leave residual 2-chloroethanol in the plastic device. If these devices come into prolonged contact with tissues, as might occur with tracheotomy tubes, the possibility exists for tissue damage from leaching 2-chloroethanol. This paper reports on the effect of pure 2-chloroethanol, and various dilutions of this material, on several of the tissue types with which a tracheotomy tube might come into contact in a patient. It was found that pure 2-chloroethanol is quite destructive to most of the tissues, including ophthalmic, mucosal, muscular, and subcutaneous tissues; however, on dilution, the toxicity potential decreased sharply. dilutions of 1:10 were still toxic, but in most cases, dilutions of 1:100 were practically innocuous. A cell culture evaluation correlated almost perfectly with in vivo techniques.

The rapid chloride exchange reaction between tri-(1-naphthyl)chlorosilane and [36Cl]chloride ion in acetone

The kinetics of the reaction between tri-(1-naphthyl)chlorosilane and [36Cl]chlorides have been investigated by means of a flow–quench technique in acetone at 25·0°. It is shown that the reaction is bimolecular and that the kinetically important chloride species is free chloride ion. The rate-depressing effect of inert salts is interpreted in terms of the suppression of the ionization of the chloride salt. Hydrogen chloride also slows the reaction; conductivity and kinetic evidence is presented to show that this is due to formation of the ion HCl2– in solution.

Octahedral chromium(III) complexes in dipolar aprotic solvents. I. The isomerization of cis- and trans-Dichlorobisethylenediamine-chromium (III) ions in anhydrous NN-dimethylformamide

The kinetics and mechanism of the isomerization of cis- and trans- dichloro- bisethylenediaminechromium(III) ions, cis- and trans-[CrCl2 en2]+, have been investigated in anhydrous NN-dimethylformamide (DNF). The complex cis- chlorodimethylformamidebisethylenediaminechromium- (III), cis-[CrCl(DMF) en2]2+, is found to be a necessary intermediate and to remain a significant part of the system at equilibrium. The equilibria are found to depend on the concentration of free chloride ion as has been found in the comparable cobalt system.��� Activation parameters have been determined for isomerization reactions using both the cis- and trans-(CrCl2 en2)+ ions as starting materials and for the chloride entry reaction into the cis-[CrCl(DMF) en2]2+ ion which has been isolated as cis-[CrCl(DMF) en2](ClO4)2,R2O.