Ammonium Thiocyanate Solution Research Articles

900 MPa 級低合金鋼 SCM435 の引張特性に及ぼす水素の影響

We investigated the effect of hydrogen on the tensile properties of a quench-tempered low-alloy steel, SCM435, with the tensile strength of 930 MPa used for hydrogen storage cylinders. Tensile specimens were machined from a cylinder with the inside and outside diameters of 245 and 315 mm. The specimens were immersed in a 20 mass% aqueous solution of ammonium thiocyanate (NH4SCN) at 313 K for 48 hours and then charged with hydrogen. Tensile tests were performed in the air at room temperature. The cross head speed was ranged from 0.01 to 100 mm/min. Hydrogen-charged specimens were hold in the air for a period of 1 and 300 hours. The 0.2% proof stress and tensile strength for the hydrogen-charged specimens were similar to those for the uncharged specimens, whereas the reduction of area was lower in the hydrogen-charged specimens than in the uncharged specimens. Thermal desorption spectroscopy showed that the residual hydrogen contents in the hydrogen-charged specimens fractured by tensile tests were between 0.14 and 0.93 mass ppm. The reduction of area of the hydrogen-charged specimens decreased linearly with increasing residual hydrogen content. Scanning electron microscopy showed that the cup-corn fracture occurred in the hydrogen-charged and the uncharged specimens and that the fracture surfaces were covered with dimples. The normal stress fracture area in the center of the hydrogen-charged and uncharged specimens was almost the same. The shear stress fracture area near the specimen surface was wider in the hydrogen-charged specimens than in the uncharged specimens. This means that hydrogen enhances slip deformation near the specimen surface and resulted in the lower reduction of area in the hydrogen-charged specimen. We therefore concluded that the hydrogen embrittlement behavior of the 900-MPa-class SCM435 steel was explained by the hydrogen enhanced localized plasticity model rather than by the lattice decohesion model.

DSC and conductivity studies on PVA based proton conducting gel electrolytes

An attempt has been made in the present work to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH4SCN) solution and characterize them. DSC studies affirm the formation of gels along with the presence of partial complexes. The cole-cole plots exhibit maximum ionic conductivity (2.58 × 10−3 S cm−1) for gel samples containing 6 wt% of PVA. The conductivity of gel electrolytes exhibit liquid like nature at low polymer concentrations while the behaviour is seen to be affected by the formation of PVA-NH4SCN complexes upon increase in polymer content beyond 5 wt%. Temperature dependence of ionic conductivity exhibits VTF behaviour.

Specific determination of ferbam residues in fog-water

A specific method for the determination of a fungicide, i.e. iron(III) dimethyldithiocarbamate (ferbam) in fog-water samples is described. The method is based on the releasing of equivalent amount of iron from the fungicide and subsequently determination by spectrophotometrically or by flame-atomic absorption spectrometrically (flame-AAS). The fungicide was extracted with chloroform/toluene from the samples and digested with nitric acid. For spectrophotometric determination, the solution was then treated with ammonium thiocyanate solution in presence of the surfactants and absorbance was measured at 475 nm. Whereas, the digested solution was directly applied for flame-AAS determination of ferbam. The molar absorptivity in terms of ferbam was determined to be (3.49)×10 4 l mol −1 cm −1. The detection limits for spectrophotometric and flame-AAS methods were calculated to be 62 and 111 ppb ferbam (R.S.D. <1 and <3%), respectively. Whereas, the optimum concentration ranges for the analysis of ferbam are 4–120 and 1.5–55 μg in final volume, respectively. The methods are freed from interference of almost all ions [including Fe(II) and Fe(III)], which can commonly associate with ferbam in fog-water. The methods have been successfully applied to fog samples collected from agriculture sites of Raipur (central India).

Stress corrosion cracking and hydrogen embrittlement susceptibility of an eutectoid steel employed in prestressed concrete

The stress corrosion and hydrogen embrittlement behavior of AISI 1080 steel employed in concrete prestressing tendons was studied with different experimental techniques. A simulated concrete pore solution, with and without contaminants such as chloride, sulfate and thiocyanate ions was used. For comparison purposes the standard 20% ammonium thiocyanate solution was also employed. Polarization curves, slow strain rate tests and fracture mechanics tests were used to evaluate the influence of parameters such as potential, temperature (between 0 and 100 °C), and tempering temperature of the steel. The results have shown that the fracture mechanism of the stress corrosion cracking process is associated with hydrogen action.

Flow-injection simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on photochemical reactions of thiocyanato-complexes

The flow injection analysis systems have been developed for the simultaneous determination of iron(III) and copper(II) and of iron(III) and palladium(II) based on the photochemical reactions of their thiocyanato-complexes. In the first system, a sample solution was injected in to nitric acid solution and mixed with ammonium thiocyanate solution, followed by spectrophotometric monitoring of the thiocyanato-complexes formed. Another aliquot of the same sample solution was injected and the thiocyanato-complexes formed in the same way were irradiated by UV light before spectrophotometric monitoring. In another system, the absorbance of thiocyanato-complexes formed by each sample injection was monitored with two flow cells aligned with the same optical path before and after UV irradiation. The difference in the extent of photochemical decomposition of the thiocyanato-complexes enabled simultaneous determinations of iron(III) and copper(II) and of iron(III) and palladium(II) at levels of several μg ml −1 to some tens μg ml −1 in their admixtures. Sample throughputs are 40 and 20 h −1 by the former and latter systems, respectively.

Solvent extraction of uranium(VI) using dibenzo-18-crown-6 in nitrobenzene from ammonium thiocyanate medium

Solvent extraction of uranium(VI) from aqueous solutions of ammoniumthiocyanate has been investigated in the presence of dibenzo-18-crown-6. Uranium(VI)was quantitatively extracted from 1.0M ammonium thiocyanate using 0.01M dibenzo-18-crown-6in nitrobenzene. Back extraction of U(VI) was quantitative with various strippingagents. Separation of U(VI) from other elements was achieved from binary aswell as multicomponent mixtures. Uranium was determined in monazite sand andsyenite rock samples. The method is very simple, rapid and highly reproducible(approximately ±2%).

Cerium(IV) ammonium nitrate mediated thiocyanation of dienes: Some interesting observations

Various 1,3-dienes when treated with a solution of cerium(IV) ammonium nitrate and ammonium thiocyanate in acetonitrile afforded the isothiocyanatothiocyanates via a [3,3] sigmatropic rearrangement. Electron rich dienes afforded the γ-thiocyanato-α,β-unsaturated carbonyl compounds under similar experimental conditions.

Structure and optical properties of molybdenum disulphide (MoS2) thin film deposited by the dip technique

Molybdenum dichalcogenides appear to be very promising semiconductor materials for various applications such as solar cells [1, 2], rechargeable batteries [3] and solid lubricants for metallic and ceramic surfaces in environments where hydrocarbon or other fluid-based lubricants are unsuitable, such as in high vacuum or high temperature applications [4, 5]. They have also been widely used in space-technology where their low co-efficient of friction in vacuum is of particular value [6]. These applications arise from the optical, electrochemical and mechanical properties of these compounds. They exhibit a layer-type structure in which monolayers of Mo are sandwiched between monolayers of sulphur, which are held together by relatively weak van der Waals forces. These materials have band gaps (1.78 eV) well-matched to the solar spectrum [7]. A number of methods exist for the production of MoS2 thin films, including sputtering [8–10], electrochemical deposition [7, 11], and pulsed laser deposition [12–15]. In this communication, preliminary results on structural and optical properties of MoS2 thin films produced by a dip-coating [16, 17] technique are reported. In the film deposition process the substrate was first immersed and then withdrawn vertically from the freshly prepared methanolic solution of ammonium molybdate and ammonium thiocyanate at a controlled speed of about 1.33 mm/s with the help of a pulley and geared motor. The substrate with the liquid layer adhering to it was then transferred to a high temperature furnace under atmospheric conditions for heat treatment. The chemicals reacted on the substrate and form the desired solid film according to the following reaction.

Solid‐liquid extraction behavior of trivalent rare earths by tributyl phosphate at high temperatures

Solid–liquid extraction behaviors of trivalent rare earths (La–Lu, Y) from ammonium thiocyanate solution by tributyl phosphate using molten paraffin wax as diluent were studied and optimum extraction conditions were determined. In 10 mL of aqueous RE3+ solution where CRE(III) = 4.0 × 10−3 mol·L−1, when additions of tributyl phosphate and ammonium thiocyanate are 5.00 mL and 2.80 g, respectively, extraction distribution ratios are over 10. The procedure can be used for rapid extraction separation of rare earths. An extraction mechanism was also investigated, and the complex species extracted into organic phase is RE(TBP)(SCN)(NO3)2. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 229–233, 1999

Direct synthesis and crystal structure of zinc thiocyanate complexes with 1,4diazabicyclo(2,2,2)octane

A direct method of synthesis of zinc thiocyanate complexes with 1,4-diazabicyclo(2,2,2) octane (or triethylenediamine, Ten) is reported. The main peculiarities of interaction of zinc oxide with non-aqueous (methanol, acetonitrile, N,N-dimethylformamide = DMF, dimethylsulfoxide = DMSO) solutions of ammonium thiocyanate in the presence of Ten were investigated. The crystal structures of the compounds [Zn 2(NCS) 4(NH 3) 2Ten] ( I), (HTen) 2[Zn(NCS) 4] ( II) and [Zn(NCS) 2(Ten)DMSO] ( III) were determined by X-ray diffraction. The complexes contain four ( I) and five ( III) coordinate zinc atoms linked by μ 2-bridging nitrogen atoms of Ten forming the dimeric and polymeric molecules respectively; the complex ( II) has an ionic-type crystal lattice with (HTen) + cations and [Zn(NCS) 4] 2− anions.

Electrochemical oxidation of thiocyanate in a two-phase electrolyte

A two phase electrolysis method has been developed for preparation of thiocyanating reagent. The electrolyses were carried out using graphite electrodes using a two phase electrolytic medium made up of an aqueous solution of ammonium thiocyanate in 0.25m H2SO4 and a nonaqueous solvent. The effect of experimental parameters, such as temperature and duration of electrolysis, nature of the nonaqueous solvent and volume fraction of the nonaqueous phase, on the process current efficiency were studied. The voltammetric studies in the nonaqueous phase established that trithiocyanate, (SCN)3−1, was produced in the aqueous phase and was subsequently extracted into the non-aqueous phase.

塩基性チオシアン酸アンモニウム溶液による銀の溶解

The effect of oxidizing agent, concentration of ammonium thiocyanate, pH and the temperature on the dissolution of silver in basic ammonium thiocyanate solution were studied.The following have been concluded: 1. Cu (II) and oxygen gas are necessary to dissolve silver effectively.2. Dissolution rate of silver is proportional to the concentration of thiocyanate at lower concentrations of thiocyanate, but it becomes constant independently of the concentration at higher concentrations.3. When the concentration of thiocyanate is high enough to make the dissolution rate of silver independent of the concentration, the dissolution rate increases almost proportionally to the increase in the concentration of Cu (II).4. When the rate is proportional to the concentration of thiocyanate, the activation energy obtained is rather high and the rate determining step is assumed to be the chemical reaction of thiocyanate ion with silver on its anodic sites on the surface of silver particles. 5. When the rate dissolution is almost proportional to the concentration of Cu (II), the rate determining step is the diffusion of Cu (II) ions to the surface of silver particles.6. Overall reactions are considered as follows: Ag+Cu (NH3) 42++6SCN-=Ag (SCN) 43-+Cu (SCN) 2-+4 NH3 Cu (SCN) 2-+4 NH3+H++1/4 O2=Cu (NH3) 42++2SCN-+1/2 H20 These phenomena are quite the same as those of the dissolution of silver in acidic thiocyanate solution using Fe (III) as oxidizing agent.

Mechanism for selective ammonia transport through poly(vinylammonium thiocyanate) membranes

Ammonia diffuses selectively through poly(vinylammonium thiocyanate) membranes. This high selectivity occurs because the membranes react with ammonia to produce a solution of poly(vinylamine) and ammonium thiocyanate, a salt in which ammonia is highly soluble. Liquid membranes made of ammonium thiocyanate and membranes of poly(vinyl alcohol) impregnated with ammonium thiocyanate show similar behavior. None of these membranes operate by means of mobile carriers, the mechanisms most often responsible for selective facilitated diffusion

Solvent extraction of zinc/II/ with sulphoxides: Theoretical analysis of extraction behaviour

This paper describes a theoretical method for analyzing the behaviour of65Zn during solvent extraction from ammonium thiocyanate solutions with dialkyl sulphoxides. The mechanism of extraction of Zn/II/ from thiocyanate medium by sulphoxides may be represented by the following general equation: $$xM_{aq}^{m + } + ySCN_{aq}^ - + zS_{org} \rightleftharpoons [M_x /SCN/_y ]^{mx - y} .zS_{org} $$ where Mm+ is the metal ion and S is the extractant. Expressions for the distribution coefficients were derived taking into account complexation of the metal in the aqueous phase by inorganic ligands and also the dissociation of the extracted ion-pairs in the organic phase. Using these expressions, the values of the extraction constants were determined by a least-squares fit with the experimental extraction data. From these extraction constants, the various species extracted into the organic phase were resolved. The influence of the metal concentration, temperature and the diluent on the extraction of Zn/II/ has been investigated.

Extraction of organic compounds from solid samples

Pyridine, benzene, cyclohexane, methylene chloride, dimethyl sulfoxide, dimethylformamide, and n-methylpyrrolidone have been compared for the extraction of polycyclic organic materials (POMs) from urban air, diesel, and stack particulate samples. Both sonic and Soxhlet techniques have been examined for both natural environmental particulates and particulates spiked with selected POMs. The extraction results vary for different polycyclic compounds adsorbed on different solid matrices, so no single solvent or extraction technique could be unambiguously recommended. However, comparative average results for 14 compounds spiked onto fly ash at 0.1, 0.25, and 1.0 ..mu..g/g showed pyridine to have 1.5 times more extraction efficiency than benzene. These and other reported results suggest that pyridine deserves more attention as an extractant for particulate samples. In separate tests, recoveries of POMs from fly ash were not improved by deactivation with aqueous solutions of ammonium hydroxide, thiocyanate and carbonate, and sodium nitrite prior to the extraction. 39 references, 5 tables.

Note EXTRACTION EQUILIBRIUM OF MERCURY(II) FROM AQUEOUS AMMONIUM THIOCYANATE SOLUTION WITH TRIISOBUTYLPHOSPINE SULFIDE

ABSTRACT The extraction equilibrium of mercury(II) from aqueous ammonium thiocyanate solution with triisobutyl-phosphine sulfide(=TIBPS=S¯) in toluene has been measured at 303 K. It was found that mercury(II) is extracted according to a solvation reaction by TIBPS as a mercurydl) :TIBPS 1:2 complex, Hg(SCN)2S2, as follows: The extraction equilibrium constant, Ke, was evaluated as Ke = 1.8 × 106 (dm3/mol)2.

Comparative studies on the ion exchange behaviour of UO2(II), Ce(III) and Am(III) with Chelex-100 from thiocyanate media

The distribution of UO22+, Ce3+ and Am3+ between Chelex-100 and 0.2 and 5.0M ammonium thiocyanate solutions of different hydrogen ion concentrations has been investigated. The results obtained are compared with parallel experimental results using the anion exchanger Dowex-1×4 and the cation excharger Dowex-50×8. It is found that Chelex-100 can act as anion exchanger at pH<2 and as cation and chelate exchanger at higher pH. A main feature of the distribution results of UO22+, Am3+ and Ce3+ with Chelex-100 is the very high distribution coefficient for the three cations at pH higher than 3.5 from aqueous solutions containing 0.2 or 5.0M ammonium thiocyanate.

Solvent extraction separation of In/III/-Tl/III/ and Hg/II/-Cd/II/-Co/II/ with sulphoxides

Solvent extraction studies have been made on some metals: In/III/-Tl/III/ and Hg/II/-Cd/II/-Co/II/, from ammonium thiocyanate solutions by dialkyl sulphoxides. Separation of these metals from one another can be achieved by suitable choice of the extracted conditions. The nature of the extractable metal species has been elucidated.

Solvent extraction of Cobalt/II/ from thiocyanate solutions by sulphoxides

Abstract The extraction of cobalt/II/ from ammonium thiocyanate solutions by di-n-pentyl sulphoxide /DPSO/, di-n-octyl sulphoxide /DOSO/ and their mixtures in carbon tetrachloride has been studied. The species extracted were found to be Co/SCN/2. 4S /where S=DOSO or DOSO/. Synergic effects have been observed which are ascribed to the formation of mixed ligand metal complexes. The influence of the metal concentration, temperature and the diluent on the extraction of cobalt/II/has been investigated.

SOLVENT EXTRACTION OF INDIUM(III) FROM THIOCYANATE SOLUTIONS BY SULPHOXIDES

The extraction of cobalt/II/ from ammonium thiocyanate solutions by di-n-pentyl sulphoxide /DPSO/, di-n-octyl sulphoxide /DOSO/ and their mixtures in carbon tetrachloride has been studied. The species extracted were found to be Co/SCN/2. 4S /where S=DOSO or DOSO/. Synergic effects have been observed which are ascribed to the formation of mixed ligand metal complexes. The influence of the metal concentration, temperature and the diluent on the extraction of cobalt/II/has been investigated.