Analytical aspects of organic acids

Summary Phenyl acetic acid has been found to be a selective reagent for the estimation of zirconium. The acid gives a white crystalline precipitate which is quantitative between pH values of 3.00 to 5.40. As the composition of the precipitate varies somewhat, direct weighing is not possible and the compound is ignited to the oxide. The ions Be²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Mg²⁺, Ni²⁺, and Co²⁺ do not interfere, whereas the ions Fe³⁺, UO₂ ²⁺, Cr³⁺, Ba²⁺, Au⁺, Al³⁺, V₂O₄ ²⁺, Ti⁴⁺, Sn²⁺, and Ba²⁺ cause interferences in the estimation.

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Zusammenfassung Zur gravimetrischen Bestimmung von Zirkonium wird Phenylessigsäure empfohlen. Die weiße, kristalline Fällung ist im pH-Bereich 3,00–5,40 quantitativ. Infolge schwankender Zusammensetzung des Niederschlages ist eine direkte Wägung nicht möglich; er wird daher zum Oxid verglüht. Folgende Ionen stören nicht: Be²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Mg²⁺, Ni²⁺ und Co²⁺; dagegen verursachen Fe³⁺, UO₂ ²⁺, Cr³⁺, Ba²⁺, Au⁺, Al³⁺, V₂O₄ ²⁺, Ti⁴⁺, Sn²⁺ und Ba²⁺ Störungen bei der Bestim mung.

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Part VI: See Z. analyt. Chem. 175, 29 (1960).     

Gravimetric estimation of zirconium by m-Ethyl phenoxyacetic acid

Summary m-Ethyl phenoxyacetic acid is found to be a selective reagent for the estimation of zirconium. Even 2.2 mg of zirconia can be easily estimated. The composition of the precipitate is somewhat variable and so direct weighing is not possible. The difficulty is overcome by igniting the precipitate and weighing it as oxide. Zn, Ca, Ba, Be, Mg, UO₂, Th, Mn, Co, Ni, Al, Ce, Ti, Fe, and Sn ions do not interfere in the precipitation of zirconium. Cr and V₂O₂ are coprecipitated with zirconium but they can be easily removed by double precipitation. Quantitative results are also obtained even in the presence of SO₄.     

Analytical aspects of some organic acids Part III

Summary m-Phenylenedioxydiacetic acid gives a white precipitate with thorium even in the absence of an electrolyte which is quantitative up toph 4. Be²⁺, Mg²⁺, Ca²⁺, Zn²⁺, Pb²⁺ and Mn²⁺ ions are removed by single precipitation and Al³⁺, UO₂ ²⁺ and trivalent cerite earth ions are removed by double precipitation. Sn²⁺, Sn⁴⁺ and Cr³⁺ ions interfere.Part II: See. Z. analyt. Chem.165, 343 (1959).     

Sol-gel synthesis of carbonate-containing zirconium(IV) hydroxide and its sorption properties toward alkaline-earth elements

Carbonate-containing zirconium hydroxide with a CO₂ content of up to 0.5 mol per mole of ZrO₂ was prepared by the sol-gel procedure. The sorption power of the carbonate-containing zirconium(IV) hydroxide toward Sr²⁺, Ca²⁺, and Mg²⁺ ions was studied. The effect of pH and electrolyte concentration on the sorption power was examined.     

Preparation and ion-exchange properties of zirconium tungstoarsenate

A new inorganic ion-exchanger, zirconium tugnstoarsenate, has been synthesized which has been characterized by chemical analysis, thermogravimetry, X-ray and infrared spectroscopy. The ion exchanger has been found to be stable in acids and neutral salt solutions. The K_d values for 30 metal ions have been determined at pH 3–4 which show that the exchanger has high affinity for UO ₂ ²⁺ , ZrO²⁺, Cs⁺ and Tl⁺ ions. The variation of K_d for a number of metal ions as a function of concentration of nitric acid and ammonium nitrate has been investigated to elucidate the probable exchange mechanism and to work out conditions for elution. Some binary separations, viz. Sr²⁺−Cs⁺, Sr²⁺−Rb⁺, Sr²⁺−Y³⁺, Fe³⁺−Al³⁺, Fe³⁺−Zn²⁺ and Zn²⁺−Hg²⁺ in trace amounts have been carried out on the column of the exchanger which demonstrate the utility of the exchanger in radionalytical and analytical chemistry.     

Sol–gel preparation and white up-conversion luminescence in rare-earth doped PbF<Subscript>2</Subscript> nanocrystals dissolved in silica glass

89.5(SiO₂)10(PbF₂)0.5(REF₃) silicate glasses have been prepared using room temperature sol–gel processing of Si(OCH₂CH₃)₄, Pb(CH₃COO)₂·3H₂O, RE(CH₃COO)₃·nH₂O and trifluoroacetic acid as a fluorinating agent, where RE stands for rare-earth ions, such as Yb³⁺, Er³⁺, Ho³⁺, Tm³⁺, or combinations of those ions. On heat treatment of these glasses at about 300–400 °C, the rare-earth doped spherical PbF₂ nanocrystals precipitate within SiO₂ glass matrix providing transparent nano-structured glass–ceramics, while the diameter of the nanocrystals can be set in the range from 5 to 25 nm by varying time and temperature of the heat treatment. The structural and photoluminescence studies confirm the incorporation of rare-earth ions into the PbF₂ nanocrystals and white and tuneable colour up-conversion luminescence has been detected in case of Yb³⁺-Er³⁺-Tm³⁺ and Yb³⁺-Ho³⁺-Tm³⁺ co-doped nanocrystals by varying dopant ratio and pump power.     

Synthesis and ion-exchange properties of zirconium antimonate

Samples of zirconium antimonate have been prepared under varying conditions of precipitation. Their properties, composition, and ion-exchange behaviour are reported. The 1g K_d vs. pH curves are given for Rb⁺, Cs⁺, Zn²⁺, Ca²⁺ and Tl³⁺ ions. The distribution coefficients of 26 metal ions have been measured and several separations of analytical and radiochemical importance achieved.     

Inorganic composite membranes for electrodialytic desaltination

Application of inorganic composite membranes in electrodialytic desaltination of dilute solutions containing Na⁺, Ca²⁺, Mg²⁺, Cl^?, and SO ₄ ^2? ions was studied. The membranes are based on an oxide ceramic containing hydrated zirconium(IV) oxide as an ion-exchange component. The limiting currents were estimated theoretically.     

Observation of DC field-evaporated ion species extracted from transition metal nitride thin film deposited on tungsten-tip

The ion species extracted from transition metal nitride thin films were investigated in order to understand the field evaporation mechanism of nitrogen in atom probe analysis. Nitrides of group IV transition metal, ie, titanium (Ti), zirconium (Zr), and hafnium (Hf) nitrides, were chosen for analysis, owing to their good electrical conductivities. The samples were prepared by sputtering deposition of nitride thin film on a tungsten needle. Measurements were performed at 3 different direct current voltages, and for each voltage, we observed different ion species. For TiN and ZrN, both atomic metal ions and molecular ions were detected and TiN and ZrN tended to evaporate in the form of triple-charged molecular ions. For ZrN, Zr²⁺, Zr³⁺, ZrN³⁺, and (ZrN)₂³⁺ were observed at lower direct current voltages. For a higher tip voltage, N⁺ ions were detected in addition to these ions. These results suggest that the evaporation field of nitrogen is higher than those of Zr³⁺ and (ZrN)₂³⁺. In the analysis of an HfN tip, no ions could be detected. These results can be explained in terms of the differences between evaporation fields that were roughly estimated from the work functions and the bond energies of the analyzed nitrides.     

Cation binding by 2<Superscript>1</Superscript>,3<Superscript>1</Superscript>-diphenyl-l <Superscript>2</Superscript>,4<Superscript>2</Superscript>-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2 (2,3),3(3,2)-diindolizinacyclopentadecaphane and its acyclic analog

The binding of cations Li⁺, Na⁺, K⁺, Cs⁺, Ag⁺, Zn²⁺, Ni²⁺, Co²⁺, NH₄ ⁺ (group I), H⁺, Mg²⁺, Al³⁺, Ga³⁺ (group II), and Ca²⁺, Pb²⁺ (group III) by 2¹,3¹-diphenyl-l ²,4²-dioxo- 7,10,13-trioxa-l,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane (1), which contains two indolizine and two quinoxaline fragments and 3,6,9-trioxaundecanes spacer, and by its acyclic analog (2) was studied using cyclic voltammetry in MeCN/0.1 M Bu₄NBF₄. It was concluded that the ions of group I are not bound by these compounds, the ions of group II exhibit the reversible redox-switched binding by the carbamoyl groups of the quinoxaline fragments, whereas the ions of group III are bound not only by the initial compounds and radical cations 1 and 2, but also by dication 1. This binding of the Ca²⁺ and Pb²⁺ ions stabilizes dication 1.     

Voltammetric study of metal ions binding by biindolizine heterocyclophanes and their acyclic analogues

The binding of ions Li⁺, Na⁺, K⁺, (group I), Mg²⁺, Al³⁺, Ga³⁺ (group II), Ca²⁺, Pb²⁺ (group III) ions, Ba²⁺ and paraquat by heterocyclophanes containing biindolizine and quinoxaline fragments connected by 3,6,9-trioxaundecane and 5,8,11,14,17-pentaoxageneicosane spacers, and also their acyclic analogues, in the acetonitrile-0.1 M Bu₄NBF₄ is studied by cyclic voltammetry. A conclusion is drawn that the ions of the group I are not bound by these compounds; the paraquat is not bound by heterocyclophane with the 5,8,11,14,17-pentaoxageneicosan spacers. For ions of the group II, reversible redox-switchable binding by the macrocycles with the 3,6,9-trioxaundecane and 5,8,11,14,17-pentaoxageneicosan spacers is observed: the initial compounds show the binding; their radical cations and dications do not. The binding of the ions of the group III and Ba²⁺ is determined by the macrocycles’ size. In particular, these ions are bound not only by the heterocyclophane with 3,6,9-trioxaundecane spacers but also by its radical cation or dication. The binding results in the corresponding dication stabilization. The heterocyclophane with the 5,8,11,14,17-pentaoxageneicosan spacers demonstrates the redox-switchable binding of Ca²⁺ and Pb²⁺ ions; no effect of Ba²⁺ ions on the cyclic voltammograms of this heterocyclophane was observed. In the ternary system “heterocyclophane with 3,6,9-trioxaundecane spacers + ions of the group II (Al³⁺, Ga³⁺) + ions of the group III (Ca²⁺, Pb²⁺)” either primary binding of the group III ion Pb2+ or concurrent binding of the ions of the group II and the group III, with the system’s reversible redox-switching from one metal complex to another, was observed.     

Enhancing Photoactivity of TiO2(B)/Anatase Core–Shell Nanofibers by Selectively Doping Cerium Ions into the TiO2(B) Core

Cerium ions (Ce³⁺⁾ can be selectively doped into the TiO₂(B) core of TiO₂(B)/anatase core–shell nanofibers by means of a simple one‐pot hydrothermal treatment of a starting material of hydrogen trititanate (H₂Ti₃O₇) nanofibers. These Ce³⁺ ions (≈0.202 nm) are located on the (110) lattice planes of the TiO₂(B) core in tunnels (width≈0.297 nm). The introduction of Ce³⁺ ions reduces the defects of the TiO₂(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce³⁺/Ce⁴⁺ couple (E°(Ce³⁺/Ce⁴⁺)=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO₂(B). Therefore, once the Ce³⁺‐doped nanofibers are irradiated by UV light, the doped Ce³⁺ ions—in close vicinity to the interface between the TiO₂(B) core and anatase nanoshell—can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge‐separation mechanism accelerates dye degradation and alcohol oxidation processes. The one‐pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co^2+/3+ and Cu^+/2+ ions. The doping substantially improves the photocatalytic activity of the mixed‐phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn²⁺, Ca²⁺, or Mg²⁺, does not enhance the photoactivity of the mixed‐phase nanofibers as the ions could not trap the photogenerated holes.     

Magnetic properties of the semiconducting lanthanide cuprates Ln2CuO4 and their interpretation: Evidence for a new series of planar copper antiferromagnets

The magnetic susceptibility of the semiconducting lanthanide cuprates Nd₂CuO₄, Pr₂CuO₄, Eu₂CuO₄, and Sm₂CuO₄ has been measured in the range 4–300 K. Below 300 K, the Cu²⁺ ions are ordered antiferromagnetically in the CuO₂ planes of these compounds, and the exchange interactions involving the Ln³⁺ ions are relatively weak. The suceptibility of the Ln³⁺ ions obeys the Curie-Weiss law at elevated temperatures, but deviations from this law occur at lower temperatures. An attempt is made to account for these deviations by fitting theoretical expressions for the susceptibility of isolated Ln³⁺ ions under the influence of a cubic crystal field to the experimental data. Excellent agreement is obtained for Nd³⁺ and Eu³⁺ over the entire temperature range and for Pr³⁺ and Sm³⁺ at elevated temperatures. Deviations at lower temperatures for the latter two ions may be due to structural changes, exchange interactions involving the Ln³⁺ ions, or possibly oxygen nonstoichiometry. The susceptibility parameters derived by fitting the theoretical expressions to the experimental data are also discussed. It is concluded that these compounds form an interesting new series of planar Cu²⁺-ion antiferromagnets.     

Bismuthiol II as an analytical reagent

Summary The reagent Bismuthiol II completely precipitates palladium at a maximum acidity of 0.3 N in nitric acid, 0.5 N in hydrochloric acid or 1 N in sulphuric acid and also at a maximum p_H of about 8.0. The palladium complex Pd (C₈H₅N₂S₃)₂ is stable even up to a temperature of about 250° C. From a mineral acid solution palladium can be estimated in presence of ions of Fe²⁺, Al, Cr, Th, Ce³⁺, Zr, Ti⁴⁺, UO₂ ²⁺, Be, Mn, Co, Ni, Mg, P0₄ ^3–, AsO₄ ^3–, rare earths, alkalis, alkaline earths, Ce⁴⁺, WO₄ ^2– and MoO₄ ^2– that are not ordinarily precipitated by the reagent. At a p_H of 4.75 to 8.2, EDTA, Na-salt, keeps in solution, besides the above ions, the ions of Tl+, Cu²⁺, Pb, Bi³⁺, As³⁺, Sb³⁺, Zn, Cd, Fe³⁺, CrO₄ ^2–, AsO₃ ^3– and VO₃ ^–. Tartrate, however, at a p_H 6.2–8, keeps all the ions including Sn⁴⁺ in solution except of course Tl⁺, Cu²⁺, Pb and Cd. Separation from Ce⁴⁺, WO₄ ^2–, MoO₄ ^2– and AsO₄ ^3– at a low p_H require the presence of tartrate. Ag⁺, Hg²⁺ and also Pb may be complexed with potassium iodide at a p_H 6–8. Tl⁺ and Ag⁺ may also be separated in presence of cyanide in an acetate buffer when palladium remains in solution and from which it may be re-precipitated by acidification.Part II see Z. analyt. Chem. 154, 413 (1957).     

Investigation of metal activation of a partially purified polyphenol oxidase enzyme electrode

Biosensors can be developed using different biological materials and immobilization technologies. Enzymes are generally used in biosensor construction, and some enzymes need metal ions or small organic molecules as a cofactor for their activation. Polyphenol oxidases can be activated by several metal ions such as Cu²⁺, Mg²⁺, Zn²⁺, Mn²⁺, and Ni²⁺. In this study, a new measurement method has been developed that is based on the metal ion activation of the polyphenol oxidase enzyme used in the biosensor preparation, especially to determine the concentration of Mg²⁺ ions. Polyphenol oxidase (PPO) (EC 1.10.3.1) was partially purified from potato (Solanum tuberosum) by using (NH₄)₂SO₄ precipitation, dialysis, and lyophylization processes. As a result of this processes, approximately 30-fold purification was achieved for PPO. For construction of the biosensor, the enzyme was immobilized on the dissolved oxygen probe membrane using gelatin and glutaraldehyde (2.5%). Using the biosensor, we obtained responses for catechol in the absence and presence of Mg²⁺ ions. Differences between the biosensor responses were related to the concentration of Mg²⁺ ions. The biosensor response depends linearly on concentration of Mg²⁺ ions between 0.05 and 7.5?mM. In the optimization studies, phosphate buffer (pH 7.0, 50?mM) and 35°C were determined to be the optimum conditions. This project will be a novel biosensor study and it might bring a new term, ‘activation based biosensor’ into the biosensor area.     

A Colorimetric and Fluorimetric Chemodosimeter for Copper Ion Based on the Conversion of Dihydropyrazine to Pyrazine

In this research, we successfully synthesized and fully characterized the new compound 5,8,13,16,21,24‐hex‐(triisopropylsilyl)ethynyl)‐6,23‐dihydro‐6,7,14,15,22,23‐hexaza‐trianthrylene ( HHATA , brown color in a mixed solvent of CH₂Cl₂/CH₃CN 1:1, v/v, weakly blue fluorescent), which can be easily oxidized to 5,8,13,16,21,24‐hex‐(triisopropylsilyl)ethynyl)‐6,7,14,15,22,23‐hexazatrianthrylene ( HATA ) (yellow color in CH₂Cl₂/CH₃CN 1:1, v/v), red fluorescent) by Cu²⁺ ions. This reaction only proceeds efficiently in the presence of Cu²⁺ ions when compared with other common metal ions such as Fe³⁺, Co²⁺, Mn²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Ag⁺, Mg²⁺, Ca²⁺, K⁺, Na⁺, and Li⁺. Our result suggests that this reaction can be developed as an effective method for the detection of Cu²⁺ ions.     

Aqueous Chemistry of Zirconium(IV) in Carbonate Media

The interactions between carbonate ions and zirconium oxychloride are studied by potentiometry, dialysis, and ¹³C‐ and ¹⁷O‐NMR spectroscopy in aqueous media. The nature of the soluble carbonatohydroxo complexes depends on the proportions of hydrogencarbonate and carbonate ions in solution before the addition of zirconium oxychloride. Carbonate media lead to polynuclear entities containing no more than two complexed carbonate ions per Zr⁴⁺. The presence of hydrogencarbonate favors the formation of less condensed and more carbonated complexes such as [Zr(CO₃)₄]⁴⁻. The polycondensation degree of the species decreases when the number of carbonates linked per Zr⁴⁺ increases. In all complexes, the carbonate is bidentate, and the metal atoms are linked via hydroxo bridges. The complexation of carbonate with Zr⁴⁺ occurs for a total carbonate concentration higher than 0.1M . Consequently, in natural medium, the speciation of this metal is governed only by the formation of hydroxo complexes.     

Reexamination of the theory of exaltation of the migration current by preceding electrode reactions

The effect of the preceding current of Hg(CN)₂, CdSO₄, ZnSO₄, and HCl on the K⁺ wave, of Hg(CN)₂ and CuSO₄ on the Cd²⁺ wave, of CdSO₄ on the Zn²⁺ wave, and of Hg(CN)₂ and CdSO₄ on the IO^?₃ wave was investigated. No exaltation of the Cd²⁺ wave was observed and only small variations of the Zn²⁺ and IO^?₃ waves. The increase of the K⁺ waves was roughly in accord with the prediction of the theory of the so-called exaltation of migration currents by preceding electrochemical reactions. However, the exaltation can be explained by concomitant reactions of K-amalgam with water and electrochemical reduction of hydrogen, which are accelerated by other ions (and also by the ions involved in the preceding reactions) and which, consequently, invalidate the equation of the exaltation of migration currents.     

Exploring LiZnNbO4 as a Host for New Colored Compounds: Synthesis,Structure, and Material Properties of NbZn1-x Mx LiO4 (M=Mn,Co, Ni,Fe) and Nb1-ySby Zn1-x Mx LiO4 (M=Co,Ni)

The non - centrosymmetric tetragonal inverse spinel structure of LiZnNbO₄ has been explored with a view to prepare new colored compounds. The substitution of Co²⁺, Ni²⁺, Fe²⁺, Mn²⁺, and Cu²⁺ ions were attempted in the place of Zn²⁺ ions and Sb⁵⁺ ions in place of Nb⁵⁺ ions. The studies indicated that 0.75 Zn²⁺ ions in LiZnNbO₄ can be replaced by Co²⁺ ions and 0.5 Zn²⁺ ions in LiZnNb_0.5Sb_0.5O₄ compound. The substitution of Co²⁺ ions gives rise to different shades of blue color in Li(Zn_1-xCo_x)NbO₄ compounds and from ink blue to blue-green color in Li(Zn_1-xCo_x)(Nb_0.5Sb_0.5)O₄ compounds. The different colors observed in the present study were explained by the traditional allowed d-d transitions as well as the metal-to-metal charge transfer (MMCT) transitions involving Nb⁵⁺ (4d⁰) ions and partially filled 3d electrons. The SHG studies indicate that the prepared compounds are SHG active. All the compounds exhibit reasonable dielectric behavior with low loss. The XPS studies confirm the oxidation states of the different substituted ions. Raman studies indicate variations in the bands due to the substitutions in the parent LiZnNbO₄ phase. Magnetic studies on the Co²⁺ ions substituted compounds suggest antiferromagnetic behavior.     

Activation and properties of Mo=O bonds in Mo/SiO2 catalysts

The existence of the charge transfer excited triplet state [Mo⁵⁺-O^-] produced by UV-irradiation of Mo/SiO₂ catalysts, and its reactivity are evidenced by experiments of photoluminescence, photoinduced metathesis, and photoreduction of CO. Mo⁵⁺ ions can be produced separately by thermal activation and O^- ions by further adsorption of N₂O on those Mo⁵⁺ ions. The latter of which are adsorbed on Mo⁶⁺ ions are found to be more reactive than O^2- of [Mo⁶⁺ =O^2-] bond. They are able either to add a molecule such as CO or C₂H₄, or to abstract hydrogen from H₂, CH₄ or trans-dicyanoethylene, or a CN group form tetracyanoethylene (TCNE). The Mo⁵⁺ ions are able to coordinate gas phase ligands when their coordination sphere possesses vacant sites. This is the case for tetracoordinated Mo⁵⁺ _4c ions arising from reduction of tetrahedral Mo⁶⁺ ions (Eq. (7)). These Mo⁵⁺ _4c ions are similar to those produced by UV-irradiaiion (Eq. (2)). In addition, if the adsorbed molecule has a sufficiently large electron affinity, such as TCNE or O₂, an electron transfer can occur (Eq. (9) and (17)). The [Mo⁵⁺-O^-] bond obtained by thermal activation is more difficult to evidence than that obtained with UV-activation because it is not detectable by EPR. However, the EPR results obtained at low temperature show that the O^- ions adsorbed on Mo/SiO₂ catalysts as well as the [Mo⁵⁺-O^-] excited triplet state obtained by UV-irradiation of 1Mo⁶⁺=O²] interact with methanol (Eq. (16)). They are consistent with the mechanism of methanol oxidation occurring at high temperature (Eq. (4)).