Concentrated Hydrochloric Acid Solution Research Articles

The crystal and molecular structure of hexachloro-tris(μ-allylthiourea) ditungsten (III) monohydrate {W2 [SC(NH2)NHCH2CHCH2]3Cl6} · H2O

A new kind of binuclear tungsten complex {W2[SC(NH2)NHCH2CHCH2]3Cl6} H2O was synthesized by mixing a concentrated hydrochloric acid solution of [W2Cl]3− with allylthiourea and investigated by X-ray structural analysis. The crystal is monoclinic, belonging to the space group P21, with the following parameters: a = 8.496(1)A, b = 18.760(2)A, c = 8.591(1)A, β = 91.36(1)' and Z = 2 with Dc = 2.297 g·cm−3. The structure was solved by heavy atom method and difference Fourier synthesis and refined by full-matrix least-squares technique to a final R factor of 0.038 for 2812 independent reflections with I ≥ 3σ(I). The result shows that in the structure each W atom forms an octahedral coordination with three Cl atoms and three bridging S atoms of the allylthiourea molecules. These two octahedra share a common face to form a binuclear complex with a very much shorter W-W bond distance (2.443(1)A), indicating a strong interaction between the two W atoms. Judging from the orientation of the thiourea ligand groups with respect to the W-S bonds, the thiourea S atoms are coordinated to the two W atoms in different manners. It is noted that one of the two W atoms is located at the point of intersection of the three thiourea planes, while the other W atom is located quite apart from these thiourea planes with three W-S bonds nearly perpendicular to each of them respectively.

Slow charge transfer associated with a fast equilibrated follow-up dimerization reaction

The influence of a fast reversible follow-up reaction on the global kinetic behaviour of an EC scheme is investigated when the C reaction is a dimerization involving the parent compound and the product of the first electron transfer. It is shown that even when the rate-determining step is the electron transfer, the C reaction exerts a strong influence on the apparent kinetics of the electron transfer, resulting in the apparent rate constant and transfer coefficient depending on the concentration. For large values of the equilibrium constant of the follow-up reaction, the initial electron wave splits into two half-electron waves, the locations of which depend on both the electron transfer rate constant and the equilibrium constant. The whole analysis is performed in the context of steady-state electrochemical methods, and the transposition of the results to transient methods is discussed. The analysis presented is exemplified by the case of Sn(IV) reduction in concentrated hydrochloric acid solutions.

X-Ray Diffraction Studies on the Structures of Hydrated Oxonium Ion, and the Chlorocobalt(II) and Tetrachlorocobaltate(II) Complexes in Aqueous Solutions

Abstract The structure of hydrated oxonium ion has been determined in a concentrated hydrochloric acid solution by the X-ray diffraction method. The oxonium ion H3O+ combines with four water molecules to form a trigonal pyramid structure in which three water molecules have an H3O+–H2O distance of 2.44 Å, while the water molecule at the apex of the pyramid is separated by 2.90 Å from the central oxygen atom of the oxonium ion. The structure of the CoCl+ determined in a relatively dilute lithium chloride solution (the Cl/Co mole ratio is 3.38) shows that the cobalt(II) ion is coordinated with five water molecules, the Co–OH2 distance being 2.14 Å. The Co–Cl distance within the complex is 2.35 Å. The CoCl42− complex has a regular tetrahedral structure both in a concentrated lithium chloride (Cl/Co=22.1) and a hydrochloric acid (Cl/Co=21.1) solutions with the Co–Cl bond length of 2.29 Å.

Transference numbers and phenomenological transport coefficients for concentrated aqueous hydrochloric acid solutions at 25�C

The transference numbers of HCl in water at 25°C have been determined up to 8 mol-kg−1 by using cells with transference. The problem of the solubility of AgCl from Ag/AgCl electrodes was avoided by employing dilute chlorine gas/iridium electrodes for T H and hydrogen gas/platinum electrodes for T Cl . The sums of the independently measured T H and T Cl values never differed from unity by more than 0.9%. The cation constituent transference number of HCl was also measured at 1M by the recently modified moving boundary method, but at higher concentrations the Soret effect produced unacceptably large current dependences. Combination of these transference numbers with literature conductances, diffusion coefficients and activity coefficients led to a new set of phenomenological transport coefficients l ij . The resulting curve for l12/c vs. c behaves more normally than did the curve based on previous transference numbers.

Anodic behaviour of titanium in acidic chloride containing media (HClNaCl). Influence of the constituents of the medium—I. Study of the stationary current. Calculation of the overall reaction orders

In concentrated hydrochloric acid solutions, the overall dissolution rate depends on the acid concentration. Using mixed electrolytes (HClNaCl) we have established the influence on the overall anodic stationary current, of each of the H + and Cl − ions. Considering the logarithmic derivative of the overall current with respect to the activities in the various constituents of the medium reveals the complexity of the reaction mechanism especially in the activity and passivation ranges.

Kinetics of etching of dislocations in magnesium orthosilicate single crystals

AbstractCleavages of undoped, doped and natural magnesium orthosilicate crystals have been simultaneously etched in concentrated hydrochloric acid solution. The lateral and normal velocities of the growth of pits were then measured at different temperatures for the varieties of crystals. The time dependence of the growth of pit dimensions is found to be linear, while the temperature dependence of the growth of pits is found to be exponential, viz. V = A exp (− E/kT). The dissolution parameters, e. g. the activation energy (E) and the pre‐exponential factor (A) for dissolution along the surface and along the dislocation lines have been computed. It is observed that: (1) the activation energy (E1) of dissolution along [001] direction is found to be greater than the activation energy (Eb) along [100] direction, irrespective of whether the crystals are doped, undoped or natural, and (2) the doping of the crystal with manganese has lowered down the activation energy (Ed) to such an extent that it is less than E1 and Eb. The implications are discussed.

The synthesis of novel dipyridazinothiazine ring systems

AbstractThe synthesis of several dipyridazinothiazines have been accomplished by: (a) cyclization in concentrated hydrochloric acid solution of the appropriate intermediates; and (b) via the Smiles rearrangement in either basic or glacial acetic acid solution of the appropriate intermediates. The following ring systems have been prepared and characterized: 10H‐dipyridazino‐[4,3‐b:4′,5′‐e]‐1,4‐thiazine, 5H‐dipyridazino[3,4‐b:4′,5′‐e]‐1,4‐thiazine, 10H‐dipyridazino[4,5‐b:‐4′,5′‐e]‐1,4‐thiazine, 5Hdipyridazino[5,4‐b:4′,3′‐e]‐1,4‐thiazine, and 10H‐dipyridazino[3,4‐b:‐3′,4′‐e]‐1,4‐thiazine.

Determination of sodium in high-purity zinc and selenium by neutron activation

A method is described for the determination of traces of sodium in high-purity zinc and selenium by neutron activation. The sample and portions of standard solution were irradiated in JRR-2 for 20 min at a thermal neutron flux of about 7 × 1013n/cm2· sec.The samples irradiated were cooled for about 2 hours.The zinc sample was etched with 5 N sulfuric acid and then dissolved in concentrated hydrochloric acid. The selenium sample was etched with aqua regia, dissolved in concentrated nitric acid, and converted to concentrated hydrochloric acid solution. The sample solution was poured into a hydrated antimony pentoxide (HAP) column (5φ × 30 mm) which was previously conditioned with concentrated hydrochloric acid. The column was washed with concentrated hydrochloric acid. Sodium-24 was adsorbed on HAP but zinc and selenium were not. The column was transferred to a polyethylene vial and its γ-activity was measured with a 3 x 3 inch NaI(Tl) detector and 400 channel pulse-height analyzer. The 2.754 MeV γ-ray photopeak of 24Na was used for the determination. The standard solutions were treated in the same way as the samples. Nuclides produced from zinc and selenium did not interfere with the determination of sodium.The proposed method was successfully applied to three NBS standard samples. A detection limit of this method was 10-3 ppm Na in zinc and selenium.

AЛьфA- И ГAMMA-PAДИOЛИЗ КOHЦEHT;PИPOBAHHЫЧ BOДHЫЧ PACT;BOPOB LiCl

α- and γ-radiolysis of concentrated hydrochloric acid solutions of LiCl has been studied and the yields of H 2 and Cl 2 have been determined. G(Cl 2) and G(H 2) have been measured in deaerated solutions for various LiCl concentratons, acidities doses rate and doses. The chlorine yield in deaerated solutions has been shown to be appreciably higher on α- than on γ-radiolysis. On changing the LiCl concentration from 3·0 to 10 mol dm −3 ([HCl] = 0·1 mol dm −3) G(Cl 2 varies on α-radiolysis from 0·7 to 1·85 molecules/100 eV, and on γ-radiolysis from 0·25 to 0·6 molecule/100 eV. In this range of LiCl concentrations the H 2 yields are on α-radiolysis 1·70-1·85 molecules/100 eV and 0·5-0·6 molecule/100 eV on γ-radiolysis. These yields have been obtained at an α-radiation dose rate I = 10 16 eV/cm 3 min and at a γ-radiation dose rate I = 10 18 eV/cm 3 min. In aerated solutions α-irradiated at the dose rate of 10 16 eV/cm 3 min G(Cl 2) aerated = G(Cl 2) deaerated; for a similar γ-dose rate the chlorine yield is actually zero. For a γ-dose rate of 10 18 eV/cm 3 min G(Cl 2) in aerated solutions is very high, e.g. in 10 mol dm −3 LiCl solution G(Cl 2) aerated = 2·75 molecules/100 eV. The relationship between the chlorine yield and the dose rate leads the authors to the conclusion that the reaction of chlorine with hydrogen peroxide plays a significant role in the mechanism of radiolysis of concentrated chloride solutions of low acidity: Cl 2 + H 2O 2 = 2H + + 2Cl − + O 2. The contribution of this reaction is the higher the lower the dose rate (within 10 15–10 18 eV/cm 3 min) and the longer the time of irradiation of the solutions. A variation in acidity of LiCl solution within 0·1-1 mol dm −3 resulted on α-radiolysis in an increase of chlorine yield and did not affect G(Cl 2) on γ-radiolysis. The mechanism of α- and γ-radiolysis of the solutions studied is discussed. In aerated solutions the balance of the radiolysis products is described by the equations: At I = 10 16 eV/cm 3 min: G(Cl 2) + G H2O 2. At I = 10 18 eV/cm 3 min: G(Cl 2) + 2 G H2O 2. In aerated solutions: At I = 10 18 eV/cm 3 min: G( Cl 2) aerated = G( Cl 2) deaerated + 1 2 G H . At I = 10 16 eV/cm 3 min: G(Cl 2) aerated = GCl 2) deaerated.

Studies on the Stability of Amides. I. Hydrolysis Mechanism of N-Substituted Aliphatic Amides

The kinetics of hydrolyses of N-substituted aliphatic amides was studied spectro-photometrically in aqueous solution at 30-95°. In concentrated hydrochloric acid solution up to 2.0M, the observed rate constants were found to increase to a constant value. Activation entropies for acidic hydrolyses of N-alkyl acetamides were largely negative, ranging -18--32 e. u. The results can be explained by a bimolecular reaction mechanism in which a nucleophilic attack by water molecules on a protonated amide molecule is the rate-determining step. In alkaline hydrolyses of N-alkyl amides, the observed firstorder rate constants k1 were found to follow a kinetic equation : k1=k2 [OH-]+k3 [OH-]2. The activation entropies were largely negative in the range from -29 to -38 e. u. and their activation enthalpies were approximately 4 to 7 kcal/mole smaller than in acidic hydrolysis. The results suggest that the rate-determining step is the nucleophilic attack on amide molecule by hydroxide ions, and that hydrolyses of N-substituted acetamides, acyl-substituted amides and esters have the same reaction mechanism. Using Taft's method, polar and steric substituent effects on the rates of hydrolyses of N-substituted acetamides are also studied.

Porous sintered titanium-base alloys

1. Powder metallurgical Ti-20% Mo-5% Cr-0.2% Pd alloys sintered at 1400°C exhibit high resistance to corrosion by hot and concentrated hydrochloric and nitric acid solutions and may be employed for the production of permeable materials. 2. To obtain coarse complex alloy powders, it is necessary to subject sintered specimens of multicomponent titanium alloys to hydrogenation and subsequent dehydrogenation.

The anodic behaviour of silver single crystal electrodes in concentrated chloride solutions

The anodic behaviour of <111> single crystal silver electrodes in concentrated hydrochloric acid solutions was examined by the faradaic impedance method. The results show that dissolution of silver as the soluble chloro-complex AgCl 4 3− occurs in 11.52 M HCl at a rate too fast to measure. In less concentrated solutions a mixture of AgCl 4 3− and the other polychloro complexes AgCl 3 2− and AgCl 2 − are formed in the ratio of their individual thermodynamic stabilities. Potentiostatic pulse results confirm these conclusions. No adsorption of Cl − was detected at potentials prior to phase formation. AgCl phase formation took place by progressive nucleation and growth of three-dimensional centres and it is likely that diffusion of Cl − is the rate determining step into the growing edge. Large changes in the real surface area of the silver were observed after the formation and reduction of AgCl nuclei.

The anodic behaviour of silver single crystal electrodes in concentrated chloride solutions

The anodic behaviour of <111> single crystal silver electrodes in concentrated hydrochloric acid solutions was examined by the faradaic impedance method. The results show that dissolution of silver as the soluble chloro-complex AgCl 4 3− occurs in 11.52 M HCl at a rate too fast to measure. In less concentrated solutions a mixture of AgCl 4 3− and the other polychloro complexes AgCl 3 2− and AgCl 2 − are formed in the ratio of their individual thermodynamic stabilities. Potentiostatic pulse results confirm these conclusions. No adsorption of Cl − was detected at potentials prior to phase formation. AgCl phase formation took place by progressive nucleation and growth of three-dimensional centres and it is likely that diffusion of Cl − is the rate determining step into the growing edge. Large changes in the real surface area of the silver were observed after the formation and reduction of AgCl nuclei.

Analysis of cadmium, lead and zinc by atomic absorption spectrometry. 1. Concentration of river water, industrial waste water, or well water by ion exchange chromatography

A method consisting of an ion exchange chromatography and the atomic absorption spectrometry has been employed for the determination of cadmium, lead and zinc in river water, industrial waste water, or well water. Various chromatographic conditions have been checked and the following procedure has been established.Five liters of water, pH being adjusted to 1.2-1.5 with a concentrated hydrochloric acid solution, was applied to a column (Dowex 50W, 40-60mesh, 100ml) at a speed of 10ml/min.Elution was performed using 600ml of a 2N hydrochloric acid solution at the flow rate of 5ml/min. The total volume of effluent was adjusted to exactly 100ml after repeated acid fuming and filtration. The concentrate was subjected to the atomic absorption spectrometry using Hitachi Model 207 Atomic Absorption Spectrometer.Utilizing the above described procedure, results obtained for river waters or industrial waste waters merging or streaming into the Jinzu River, and for well waters around this river were also shown.

Kinetics and mechanism of the reduction of molybdenum(V) by tin(II) in concentrated hydrochloric acid solutions

Kinetics and mechanism of the reduction of molybdenum(V) by tin(II) in concentrated hydrochloric acid solutions

Leucoanthocyanins and related phenolic compounds of carob pods (Ceratonia siliqua)

AbstractThe phenolic compounds present in green carob pods were separated into five components. These were characterised on the bases of solubility, mobility on paper, nature of products of hydrolysis by Penicillium tannase, nature of products yielded on heating with dilute and concentrated hydrochloric acid solution, and nature of products yielded on alkali fusion. The major leucoanthocyanins in green carob pods were highly polymerised leucodelphinidins. A large amount of, and many kinds of, hydrolysable tannins were found. Two crystalline galloyl glucose compounds were isolated.The phenolic compounds present in ripe carob pods were fractionated into four preparations. Hydrolysable tannins present in green pods, were either not found or present only in low concentrations. On the other hand, gallic acid was found in large amounts in ripe pods. The main leucoanthocyanin in ripe pods also was leucodelphinidin. The gallic acid found in ripe pods could be derived from the hydrolysable tannins in green pods by enzymic hydrolysis.

Decomposition of thiosulphate in acidified oxidants

The Wollack procedure has been used to study the competition between oxidant and acid for the thiosulphate ion. In concentrated hydrochloric acid solutions of iodine, iodate and chloramine-T, polythionates are the chief products, whereas in acid permanganate substantial amounts of other products occur. Both the concentration of the acid and the acid anion affect the course of the reaction in these solutions. Production of polythionate, an acid-decomposition product, suggests that acid decomposition successfully competes with oxidation.

Determination of uranium in electro-refined plutonium by a combined ion-exchange and x-ray fluorescence technique

Uranium is separated from plutonium by adsorption on an anion-exchange resin from a concentrated hydrochloric acid solution and is eluted from the resin, collected on a disc of cation-exchange paper, and determined by X-ray fluorescence. The lower limit of detection is 2μg of uranium, and 50μg may be determined with a recovery of 98% and a standard deviation of 3.2μg. In plutonium metal, 19ppm of uranium were found, with a standard deviation of 2 ppm (6 results).

Crystals suitable for profile angle measurement: Boric acid and picric acid in concentrated 12N hydrochloric acid

A method is described for the preparation of boric acid and picric acid crystals from concentrated hydrochloric acid solutions. The profile angles of these two compounds are reported.

Isolation of thorium in biological samples

A scheme for the isolation of subpicogram to microgram amounts of thorium from bone and soft tissue samples is described. Thorium is first collected by co-precipitation with iron(III) hydroxide and then adsorbed by a cation-exchange resin column from a concentrated hydrochloric acid solution of the precipitate. A double precipitation is necessary for bone samples whereas a single precipitation suffices for liver samples. The thorium is eluted from the column with an ammonium carbonate solution which is then evaporated to dryness to effect the isolation. Good recoveries of thorium from bone samples are obtained.