Studies with inorganic precipitate membranes. III. Consideration of energetics of electrolyte permeation through membranes

The permeability of various electrolytes through parchment-supported ferrocyanide membranes of manganese, cobalt, silver, and cadmium has been measured at 10, 15, 20, 25, and 30°C. The order of permeability at a given temperature was Cl^- > NO₃^- > CNS^- > CH₃COO^- > SO₄^2- for both monovalent and divalent cations. For any given anion, the cations followed the sequence NH₄⁺ > Li⁺ > Ba²⁺ > Ca²⁺ > Mg²⁺ > Al³⁺. This sequence has been correlated with the size of the hydrated ion. Further, the data have been considered from the standpoint of the theory of rate processes and the values for the entropy of activation (ΔS′) have been derived assuming an equilibrium distance of 3 Å in the membrane. The values of ΔS′ were all negative and decreased with increasing valence of the ions. This was interpreted to mean electrolyte permeation with partial immobilization in the membrane.     

Liquid ion-exchange extraction study of hexacyanoferrate(III) with trioctylmethylammonium chloride (aliquat-336)

Liquid-liquid ion-exchange extraction of various anions including hexacyanoferrate(III) with a chlorobenzene solution of trioctylmethylammonium chloride (TOMA-Cl; Aliquat-336 chloride) is described. The ion-pair extraction constant of TOMA-Cl (K^Q.Cl_ex = 10⁴) and the ion-exchange extraction constants of TOMA-Cl for each anion (K^Cl.X_ex) are reported. The order of selectivity of anion extraction is Fe(CN)^3-₆ (log K^Q.X_ex = 22.41) > ClO^-₄(8.47) > PAR^- (7.80) > I^-(7.32) > NO^-₃(5.81) > Br^-(5.34) > Cl^-(4.00).     

Extraction—spectrophotometric determination of boric acid with 1,8-dihydroxynaphthalene-4-sulfonic acid and zephiramine

l,8-Dihydroxynaphthalene-4-sulfonic acid (DHNS) is described as a new reagent for the extraction—spectrophotometric determination of boric acid. The reagent and its boron complex are extracted into 1,2-dichloroethane as ion-associates with tetradecyldimethyl-benzylammonium chloride (zephiramine). The extracted complex of boron—DHNS—zephiramine has the composition 1:2:3 and is stable to back-washing with 1 M sodium chloride solution (pH 9.2), whereas the excess of reagent co-extracted is removed to the aqueous phase. The apparent molar absorptivity of the complex in the organic phase is 2.45 × 10⁴ l mol^-1 cm^-1 at 341 nm, which is 1.7 times larger than that with chromotropic acid. Addition of EDTA prevents most interferences. The improved method with DHNS is successfully applied to the determination of boron as boric acid in waters. The exchange equilibrium constants,

, for the reagent and complex were also determined for four monovalent anions (X^- = Cl^-, Br^-, NO₃^-and I^-). Some of these constants are compared with those pertaining to chromotropic acid and 1,8-dihydroxynaphthalene.     

Electrochemistry in fluosol-43, a perfluorinated blood substitute: The influence of pluronic f-68 surfactant on some polarographic electrode processes

The inhibition of thaUium(I), lead(II) and cadmium(II) reductions at the dropping mercury electrode is studied in Fluosol-43 and explained as a result of surfactant adsorption. The adsorption of PIuronic F-68 on the DME, examined by electrocapillary, tensammetric and current—time curves, is diffusion-controlled. The similarity established between aqueous solutions of Pluronic F-68 at concentrations near the critical micelle concentration and Fluosol-43 confirms that the adsorption depends only on the monomer form of the surfactant. The magnitude of the inhibitory effect, evaluated from charge-transfer coefficients and rate constants, decreases in the order CD²⁺ > Pb²⁺ > Tl⁺; for the same cation, inhibition depends on the nature of the anion of the supporting electrolyte, the adsorbability of which decreases in the sequence ClO₄^- > NO₃^- > SO₄^2-.     

Ultraviolet spectrophotometric determination of tungsten(VI) with ammonium 1-pyrrolidinecarbodithioate

A simple and rapid ultraviolet spectrophotometric method is proposed for the determination of trace amounts of tungsten(VI) with ammonium 1-pyrrolidinecarbodithioate (APDC). The method is based on measurement of the absorbance of the tungsten APDC complex in fairly concentrated hydrochloric acid medium; no extraction is required. The complex is formed at an initial acidity of 6M hydrochloric acid and has an absorption maximum at 250 nm. The high absorption of the reagent blank at 250 nm disappears on decomposition of excess of reagent by heating. Beer's law is obeyed over the range 0.43–3.2 ppm of tungsten(VI). The molar absorptivity of the complex is 4.5 × 10⁴ l.mole⁻¹ .cm⁻¹ at 250 nm. Tenfold amounts of aluminium, magnesium, calcium, cobalt, iron(II), lead, silver, sodium and titanium do not interfere in the determination of 50 μg of tungsten (VI).     

Effect of the salting-out agent anion nature on the phase separation of a potassium salt–potassium bis(alkyl polyoxyethylene)phosphate–water systems

The effect the salting-out agent anion nature has on the temperature and concentration intervals of the existence of the separation area is established by analyzing the phase diagrams of pseudoternary KCl (KBr, KI, KNO₃, K₂SO₄, K₄P₂O₇)–potassium bis(alkyl polyoxyethylene)phosphate (oxyphos B)–water systems. It is concluded that the anionic salting-out capability is reduced in the order P₂O₇^4-> SO₄^2-> Cl^? > Br^?> NO₇^4-> SO₃^-> I^?. The thermodynamic parameters of phase separation used to interpret the results are calculated. The observed pattern of a change in the salting-out ability of the investigated salts relative to aqueous solutions of the surfactants is in good agreement with the lyotropic (Hofmeister) series.     

Stable free-radical complexing reagents in applications of electron spin resonance to the determination of metals: Part 2. Spin-labelled iminooxime [1]

Possibilities for the determination of metals by means of the intensity of the e.s.r. signal of the chelate-fonning reagent, spin-labelled iminomonoxime — 4-oximinomethyl-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl, have been studied. The dissociation constant of the oxime group (pK^T_a = 9.36 ± 0.08) and the reagent partition constant in the chloroform—water system (log K_D = 0.80 ± 0.11) are reported. The reagent extracts copper, cobalt and nickel into chloroform. Copper is extracted as its CuA₂, chelate (log K_D = 0.91 ± 0.03; log K_ex = -3.35 ± 0.09; log β₂, = 15.8 ± 0.2). Several properties of the spin-labelled and conventional oximes are compared. It is confirmed that a radical-containing substituent produces a strong electron-acceptor effect. Unusual extractive and e.s.r.- spectroscopic behaviour of cobalt is indicated; an adduct of the spin-labelled chelate with atmospheric oxygen seems to be formed. Methods for the determination of cobalt and nickel based on the extraction with spin-labelled oxime into chloroform and subsequent separation of the excess of reagent on a chromatographic column are described. The detection limits are 3 × 10^-7 M for cobalt and 10^-6 M for nickel.     

The extraction-spectrophotometric determination of chromium(III) with 4-(2-pyridylazo)-resorcinol

The extraction-spectrophotometric determination of chromium(III) with 4-(2-pyridylazo)-resorcinol (PAR) is described. PAR(H₂R) forms a 1:3 complex with chromium(III) in a boiling acetate buffer solution at pH 5. The complex forms an ion-association compound with tetradecyldimethylbenzylammonium ion (TDBA⁺):Cr(R)(HR)₂^--TDBA⁺ which can be extracted into chloroform, the molar absorptivity being 4.7 ·10⁴ at 540 nm. If EDTA is added as a masking agent after the Cr(HR)₃ has been formed, only iron, cobalt and nickel interfere seriously, and the method can be made specific for chromium by a preliminary extraction of these metals with cupferron. The sensitivity of the method is seven times higher than that of the diphenylcarbazide method.     

An absorptiometric determination of perchlorate by means of a novel coloured liquid anion exchanger

A novel liquid anion exchanger can be prepared from tetra-n-hexylammonium iodide and Erdmann's salt, (NH₄)[Co(NH₃)₂(NO₂)₄]. When a solution of this quaternary erdmannate in a suitable organic solvent (e_max = 15,700 at 355 mμ) is equilibrated with an aqueous solution of a salt, the coloured ermannate ion is displaced to a greater or less extent; the effect decreases in the order ClO₄^- > ClO₃^- > NO₃^- > Cl^- > SO₄^2- etc. The effects of changes in the organic solvent composition, of ionic strength, and of other variables on the position of equilibrium have been studied with a view to defining the optimum conditions for the absorptiometric determination of perchlorate ion (≧25 μ) in the presence of chlorate and other ions. Methods are proposed for eliminating those ions that form insoluble silver salts and to allow for the presence of substantial proportions of chlorate or nitrate ions.     

Use of the molybdenum-thiocyanate-rhodamine 6G ternary complex for spectrophotometric molybdenum determination without extraction

A modified thiocyanate method without extraction by using rhodamine 6G as a secondary ligand was developed. Molybdenum in 1.0×10⁻² M HCl, after the addition of ascorbic acid, was heated for 10 min in a 90 °C water bath for reduction. Suitable amounts of glycerine, Triton X-100, rhodamine 6G solutions and 2+1 (v/v) 9 M H₂SO₄+3 M KHSO₄ were added in this order. This solution was allowed to cool to room temperature and the absorbance at 570 nm was measured against a reagent blank 45 min after the addition of thiocyanate solution and the second aliquot of Triton X-100 solution. The complex was stable for at least 4 h, the order of reagent addition was important, and thiocyanate should be in large excess. Beer’s law was obeyed over the range 0.9×10⁻⁶ to 1.1×10⁻⁵ M Mo with the molar absorptivity being 1.1×10⁵ l mol⁻¹ cm⁻¹. The R.S.D. for the determination of 0.7 mg Mo l⁻¹ was 1.83% (n=8). Possible interferences of various cations and anions on molybdenum determination were studied. The proposed method was applied to the determination of molybdenum in a dental alloy, Wiron 99.     

A dispersive liquid-liquid microextraction procedure for determination of boron in water after ultrasound-assisted conversion to tetrafluoroborate

A novel, simple and green procedure is presented for the determination of boron. The method is based on ultrasound-assisted conversion of boron to tetrafluoroborate anion and the formation of an ion pair between BF₄⁻ and Astra Phloxine reagent (R), followed by dispersive liquid-liquid microextraction of the ion pair formed and subsequent UV-vis spectrophotometric detection. The conversion of boron to tetrafluoroborate anion is performed in an acidic medium of 0.9 mol L⁻¹ H₂SO₄ in the presence of 0.1 mol L⁻¹ F^- by means of 10 min of ultrasonication. The extraction of the ion pair formed between BF₄⁻ and R (1 × 10⁻⁴ mol L⁻¹ R) is carried out by dispersive liquid-liquid microextraction using 0.5 mL of amyl acetate (as extraction solvent), tetrachloromethane (as auxiliary solvent) and acetonitrile (as dispersive solvent) in a ratio of 1:1:2. The absorbance of the coloured extracts obeys Beer's law in the range 0.22-18.7 mg L⁻¹ of B(III) at 553 nm wavelength. The limit of detection calculated from a blank test (n = 10) based on 3 s is 0.015 mg L⁻¹ of B(III). The method was applied to the determination of boron in mineral waters.     

The extraction of thulium(III), dysprosium(III) and samarium(III) by dioctylarsinic acid in chloroform

Dioctylarsinic acid, HDOAA, in chloroform (0.1 M) extracts thulium(III), dysprosium(III) and samarium(III) from their aqueous solutions in the pH ranges 1–6.5, 2–7 and 4–8, respectively, with extraction coefficients of approximately 0.1 for the lowest and 10 for the highest pH. The extractability increased with increasing ionic strength for each ion and decreased in the order ClO₄^- > NO₃^- > Cl^- > SO₄^2- > acetate for solutions of the same molarity. pH-Dependence curves had slopes ranging from 1.05 to 1.87. The reagent-dependence studies gave curves with slopes between 3.60 and 5.30. The general formula [MX_n(DOAA)_m(HDOAA)_p(H₂O)_q] (X = Cl^-. NO₃^-, SO₄^2-/2, ClO₄^-, acetate, OH^-; n+m=3, m+p=4 or 5, q?0)is suggested for the extracted species.     

Radiometric trace analysis of cobalt with diethyldithiocarbamate-35S,or 203Hg

Two radiometric methods for the determination of submugram amounts of cobalt are described. (A) Cobalt is extracted from an ammoniacal solution with a zinc-diethyldithiocarbamate-³⁵S solution in chloroform. Excess reagent and interfering metals are removed with mercury(II) and cyanide. The ³⁵S in the final organic layer is a measure of the cobalt in this layer. (B) Cobalt is extracted from an ammoniacal solution with a fixed amount of zinc-DDC in chloroform. Excess reagent and complexes of foreign metals are removed by exchange with ²⁰³Hg⁺² and the ²⁰³Hg in the chloroform (compared with a blank) acts as a measure of the cobalt. Method A is applicable to 0.1 μg of cobalt and method B to 0.8 μg. As the efficiency of both processes is variable, isotope dilution with ⁶⁰Co is carried out, A 10-fold excess of foreign metals is permitted in method A and a 4-fold excess in method B ; larger amounts are previously removed, e.g. by extraction with inactive zinc-DDC from sodium hydroxide media.     

Extraction—spectrophotometric determination of trace amounts of iron in waters with pyrogallol red and zephiramine

The simple removal of excess of co-extracted reagent in the solvent extraction of metal complex anions with a quaternary ammonium salt greatly improves the determination of iron(II) with pyrogallol red and zephiramine. The method with pyrogallol red is suitable for the determination of trace amounts of iron in natural waters. The apparent molar absorptivities of the iron(II) complex in chloroform are 7.5×10⁴ and 10.3×10⁴ 1 mol^-1 cm^-1 at 560 and 298 nm, respectively. A large excess of reagent can be added, and the ternary complex can be completely extracted over the pH range 8.5–10. Masking agents allow most interferences to be suppressed. The method is suitable for the analysis of potable, river and sea waters.     

Fractal analysis of pit morphology of Inconel alloy 600 in sulphate,nitrate and bicarbonate ion-containing sodium chloride solution at temperatures of 25–100 °C

Pit morphology of Inconel alloy 600 in sulphate (SO₄ ^2-), nitrate (NO₃ ^-) and bicarbonate (HCO₃ ^-) ion-containing 0.5 M sodium chloride (NaCl) solution was analysed in terms of fractal geometry as functions of solution temperature and anion concentration using the potentiostatic current transient technique, scanning electron microscopy, image analysis and ac-impedance spectroscopy. Potentiostatic current transients revealed that the pitting corrosion is facilitated by the increase in solution temperature, irrespective of anion additives, and that it is hindered by the increase in NO₃ ^- and HCO₃ ^- ion concentration, regardless of solution temperature. Above 60 °C, it was also found that the addition of SO₄ ^2- ions impedes pit initiation, but enhances pit growth. The value of fractal dimension D _f of the pits increased with increasing solution temperature and with decreasing NO₃ ^- and HCO₃ ^- ion concentration. Moreover, the value of D _f increased above 60 °C with increasing SO₄ ^2- ion concentration. This is caused by the increase in the ratio of pit perimeter to pit area, implying the formation of pits with micro-branched shape due to the acceleration of the local attack in the pits. From the decrease of the depression parameter with increasing solution temperature, it is inferred that the roughness of the pits increased with increasing solution temperature. In addition, the depression parameter was found to increase with increasing NO₃ ^- and HCO₃ ^- ion concentration. But, above 60 °C, in the case of SO₄ ^2- ion addition, the depression parameter decreased with increasing SO₄ ^2- ion concentration. From the experimental findings, the three-dimensional pit morphology is discussed in terms of the values of D _f of the pits and the depression parameter, with respect to anion concentration and solution temperature.     

Studies on cationic micelle inhibited transimination reactions of barbituryl-azine-indandione and azine-bis-indandione with semicarbazide

The acid cataylsed transimination reactions of barbituryl-azine-indandione (BAI)and azine-bisindandione (ABI) with semicarbazide are inhibited by n-alkyl trimethylammonium bromides. At a given detergent concentration, the efficiency of inhibition increases with increasing alkyl chain-length of the detergent. Addition of counterions and alcohols increased the cetyltrimethylammonium bromide (CTAB) inhibited rate. Extent of micellar inhibition is reduced by the addition of counterions in the order NO₃^-, > Br^- > Cl^- > SO₄⁼ and by the addition of alcohols in the order n-butanol > n-propanol > ethanol > methanol. Activation parameters for the reactions in the presence of CTAB have been evaluated and compared with those obtained in the absence of detergent.     

Adsorption phenomena on polycrystalline gold electrode modified by Zn adatoms

Summary In this paper, experimental results obtained by the in-situ radiotracer and voltammetric studies of the competitive adsorption of the HSO₄^-/SO₄^2- (labeled with ³⁵S) and Cl^- (labeled with ³⁶Cl) anions on bare Au_poly substrate and Au_poly surfaces modified by the Zn adatoms in the lower pH region (pH≤4.5) are presented and discussed. In addition, some data on the formation of Zn adlayers (labeled with ⁶⁵Zn) are reported to demonstrate the complex features of the underpotential deposition (UPD) phenomenon. It has been revealed that (1) the relative adsorption strength of Cl^- ions on bare Au_poly is higher than that of H₂PO₄^-/PO₄^3- and HSO₄^-/SO₄^2- ions in the entire pH region studied; (2) anomalous tendency of the specific adsorption of anions on polycrystalline gold modified by Zn adatoms occurs at pH 4.5 as follows: PO₄^3->SO₄^2->Cl^->>ClO₄^- and (3) the UPD of Zn²⁺ ions on polycrystalline gold is measurable even from solutions containing 5 ^. 10^-8M Zn²⁺ over the entire potential range where the hydrogen evolution takes place.It is, however, plausible to assume that the coverage of the gold surface by Zn adatoms measured even at solution concentrations of c≥5 ^. 10^-4M does not exceed one monolayer.     

功能化酸性离子液体脱除模拟油品中的非碱性氮

合成了一系列功能化酸性离子液体并用于模拟油品中非碱性氮-吲哚的脱除。结果表明,离子液体的阴离子对脱氮率有较大影响,离子液体的酸性越强,对吲哚的选择性脱除效果越好,不同阴离子的脱氮率顺序为：HSO₄^- > CF₃COO^- > H₂PO₄^- > CH₃COO^-。以（CH₃CH₂）₃N（CH₂）₃SO₃HHSO₄为例,考察了剂油比、剂水比、沉降时间、反应时间和温度对油品脱氮率的影响。结果表明,在优化的工艺路线下,（CH₃CH₂）₃N（CH₂）₃SO₃HHSO₄对油品中的吲哚脱除率可达99.12%,重复使用六次后,脱氮活性未见明显降低,具有良好的稳定性,。     

A new coated-wire cobalt(II)-selective electrode based on the benzalkonium tetrathiocyanatocobaltate(II) ion pair

A cobalt-selective electrode based on the benzalkonium tetrathiocyanatocobaltate(II) ion pair is described. The response is Nemstian (slope 29.3 $\text{mV}\text{pCo}$) in the cobalt concentration range 10^-1–10^-4 M in solutions with a constant ionic strength of 3.0 M made up with KSCN at 25°C. The electrode is suitable for end-point detection in titrations of cobalt(II) with EDTA as well as for direct potentiometric determinations of cobalt(II), even in the presence of large amounts of several metal ions (Ni²⁺, Fe²⁺, Mn²⁺, Mg²⁺, Ca²⁺, Ba²⁺) and anions (HCO₃^-, Br^-, I^-, NO₃^-, SO₄^2-).     

Liquid—liquid extraction of transition metals with acylthioacetamides

The extraction behaviour of acylthioacetamides, R¹—CO—CH₂—CS—NR²R³, was studied for a series of transition metals. The highest distribution ratios were obtained with benzoylthioacetanilide. Complexes with acylthioacetamides which were completely substituted on the amide group were extracted slowly. The ranking of the extraction characteristics is related to the different pK_a values of the compounds used. Polymerization and solvation reactions can be excluded at metal concentrations of ? 10^-3 mol dm^-3 and extractant concentrations of ?10^-1 mol dm^-3, respectively. Decreasing extractability, Cu(II) > Zn(II) > Ni(II) > Co(II) > Cd(II), corresponds to the stability constants of the extracted metal chelates. Iron(III) cannot be extracted at pH ?3; Hg(II), Pd(II), and Au(III) are extracted readily over a reasonably wide pH range. The different extraction constants for zinc(II) and cadmium(II) permit an effective separation of these ions with benzoylthioacetanilide.