Mixed insoluble acidic salts of tetravalent metals

Solid amorphous Zr-, Ti- and Zr_xTi_(1–x) phosphates (where x=0.10, 0.33, 0.66, and 0.90) in various sodium forms were contacted with an excess of solid oxalic acid dihydrate to its molten state for a given time. The oxalic acid was removed by extraction and the residue was washed with redistilled water. As a result of this, crystalline forms of Zr-, Ti-, and Zr_xTi_(1–x) phosphates were obtained. Using various sodium forms of the initial samples, higher rate of crystallisation resulted than that found in case of hydrogen forms of initial samples.     

Mixed insoluble acidic salts of tetravalent metals

Mixed amorphous, glassy type, zirconium-titanium arsenate (ZrTiAs) and hafniumtitanium arsenate (HfTiAs) have been prepared. The composition and exchange capacity of the prepared samples were investigated in comparison with pure zirconium, titanium and hafnium arsenates, respectively. For the samples the Zr_xTi_(1-x)(HAsO₄)₂·2H₂O and the Hf_xTi_(1-x)(HAsO₄)₂·2H₂O compositions (where 0<x<1) were found. The exchange capacity values were found less than those for pure arsenates, but they do not change their values under the effect of high dose of gamma-radiation.     

Mixed insoluble acidic salts of tetravalent metals IV. Crystalline mixed zirconium — Titanium phosphates

Mixed crystalline alpha zirconium — titanium phosphates with variable zirconium to titanium ratios have been prepared both by the well known gel reflux method and a modified HF method. Chemical analysis, X-ray, i.r. and thermal analysis were used to characterize the materials. Exchange capacities for these ion-exchangers have been evaluated by pH-titration combined with radioisotope tract technique for Na⁺, K⁺, Rb⁺ and Cs⁺.     

Mixed insoluble acidic salts of tetravalent metals VI. Crystalline mixed zirconium-titanium arsenate and hafnium-titanium arsenate

Mixed crystalline zirconium-titanium arsenates Zr_xTi(_1–x) (HAsO₄)₂·H₂O and harnium-titanium arsenates Hf_xTi(_1–x) (HAsO₄)₂ H₂O (where x=0–1) of various compositions with different Zr/Ti or Hf/Ti ratios have been prepared. The compounds have been characterized by X-ray, thermal analysis, chemical analysis, and pH-titrations. For powder X-rays, the compounds appear to be homogeneous crystalline materials with structures similar to -ZrP, -TiP or -ZrTiP. The thermograms show a loss of approximately two moles of H₂O, followed by a small loss of O₂ with probable formation of ZrO₂, As₂O₃, HfO₂, As₂O₃, ZrO₂, As₂O₅, HfO₂, As₂O₅ from which As₂O₃ and As₂O₅ are practically sublimed in two steps. The exchange capacities at r.t. are generally similar to -ZrP and -TiP but are found to be much lower in value.     

Mixed insoluble acidic salts of tetravalent metals V. Effect of gamma radiation and drying temperature on granular mixed zirconium-titanium phosphates

Solid ZrOCl₂·8H₂O was added in a slow stream to a solution of phosphoric acid or to a solution of TiCl₄ in phosphoric acid to obtain granules of amorphous Zr(HPO₄)₂·nH₂O or Zr_xTi(_1–x) (HPO₄)₂·nH₂O(where x=0.95–0.80). Half of each product had been soaked in ethanol to produce alcohol solvated materials. It was found that the particle size of the resulting materials is very similar to that of ZrOCl₂·8H₂O, in such a way that it may be controlled indirectly. These materials are suitable for ion-exchange column operations. The relatively high gamma radiation doses of⁶⁰Co source did not alter its exchange properties. pH-titrations were performed by an automatic titrimeter and the exchange capacities of alkali metal ions were determined by isotopic tracer technique. Effect of drying temperature on the ion exchange properties of Na⁺, K⁺ and Cs⁺ on the granular materials have been studied. Other characterizations were made by usual chemical analysis and thermography.     

Thermal behaviour of acidic salts of mixed tetravalent metals

The mixed amorphous glassy-type zirconium-titanium phosphates contain various quantities of adsorbed water per molecule unit. Pure zirconium phosphate lost the structural water in two steps. This character disappeared with increasing titanium content. However, glassy titanium phosphate lost its water in two steps at lower temperature in comparison with glassy zirconium phosphate.

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Zusammenfassung Das gemischte amorphe Zirkonium-Titan-Phosphat enthält pro Moleküleinheit verschiedene Mengen adsorbierten Wassers. Reines Zirkoniumphosphat verliert das strukturelle Wasser in zwei Schritten. Diese Eigenschaft verschwindet mit zunehmenden Titangehalt. Amorphes Titanphosphat verliert sein Wasser in zwei Schritten bei niedriger Temperatur im Vergleich zu amorphem Zirkoniumphosphat.

     

Thermal behaviour of acidic salts of mixed tetravalent metals

The results of investigations on intercalated crystalline zirconium phosphate are described in the literature. The behaviour of crystalline phosphates containing both zirconium and titanium metal ions has not been investigated previously. Within these investigations, the thermal behaviour of such materials has been studied in the temperature interval 25–1000 °C by simultaneous recording of TG, DTG and DTA curves. The results are presented in this paper.

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Zusammenfassung Ergebnisse über Untersuchungen an in Schichten eingelagerten kristallinen Zirkoniumphosphat sind in der Literatur beschrieben. Das Verhalten kristalliner Phosphate, die sowohl Zirkoniumals auch Titanmetallionen enthalten, wurde bis jetzt nicht untersucht. Als Teil dieser Untersuchungen wurde das thermische Verhalten solcher Materialien im Temperaturbereich 25–1000 °C durch simultanes Registrieren der TG-, DTG- und DTA-Kurven näher bestimmt, dessen Ergebnisse hier dargelegt werden.

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. , . , , 25–1000°. .

     

Thermal behaviour of acidic salts of mixed tetravalent metals

The mixed metal phosphates were synthetized by the HF method, the resulting materials being crystalline. Thermal analysis revealed that they contain almost one mole of crystalline water per molecule unit. The mode of thermal decomposition of the samples was similar to those for crystalline phosphates containing only zirconium or titanium.

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Zusammenfassung Die Mischmetallphosphate wurden mit der HF-Methode hergestellt, wobei man kristalline Substanzen erhielt. Die Thermoanalyse zeigte, daß sie fast ein Molekül Kristallwasser pro Moleküleinheit besitzen. Die Art der thermischen Zersetzung der Proben ähnelt der Zersetzung von kristallinen Phosphaten von nur Zirkonium oder nur Titan.

     

Thermal behaviour of acidic salts of mixed tetravalent metals

Mixed zirconium-titanium phosphate samples were irradiated in a gamma-radiation facility with a Co-60 source. The adsorbed dose was 10⁶ Gy. At this dose, a change in thermal bahaviour was found only for the samples intercalated withn-butylamine orn-propylamine. Further, it was found that the titanium catalysed the decomposition and the loss of organic molecules.

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Zusammenfassung Gemischte Zirkonium-Titanphosphatproben wurden in einer Gammabestrahlungskammer mit einer Co-60-Quelle bestrahlt. Die adsorbierte Dosis betrug 10⁶ Gy. Bei dieser Dosis konnte eine Veränderung im thermischen Verhalten nur für Proben mit eingelagertemn-Butylamin odern-Propylamin festgestellt werden. Weiterhin wurde gefunden, daß Titan die Zersetzung und die Abgabe der organischen Moleküle katalysiert.

     

Thermal behaviour of mixed tetravalent metal salts

In contrast with the well-known zirconium and titanium phosphates, products containing these metal ions together are unknown. To investigate the thermal behaviour of such materials, samples were synthetized with various ratios of the two metal ions. The samples were identified by means of X-ray diffraction. Their thermal behaviour was investigated in the temperature interval 25–1000 °C via simultaneous TG, DTG and DTA measurements. The data obtained are presented in this paper.

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Zusammenfassung Im Gegensatz zu den wohlbekannten Zirkonium- und Titanphosphaten sind beide Metallionen gleichzeitig enthaltende Produkte unbekannt. Zur Untersuchung solcher Substanzen wurden Proben mit unterschiedlichen Mengen der beiden Metallionen gefertigt und mittels Röntgendiffraktion identifiziert. Die Proben wurden im Temperaturbereich 25–1000 °C mittels simultaner TG-, DTG- und DTA-Messungen untersucht. Die Ergebnisse werden in dieser Arbeit mitgeteilt.

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, . . - , , 25–1000°. .

     

Liquid-liquid extraction of tetravalent zirconium from acidic chloride solutions using Cyanex 272.

The liquid-liquid extraction of zirconium(IV) from acidic chloride solutions was carried out with Cyanex 272 as an extractant diluted in kerosene. An increase of the acid concentration decreased the percentage extraction of metal, which indicates that the extraction follows ion exchange-type mechanism: MO2+(aq) + 2(HA)2(org) <--> MO (HA2)2(org) + 2H+(aq), where, M = Zr(IV); HA = Cyanex 272. The extraction of Zr(IV) increases with an increase of the extractant concentration. In a plot of log D vs. log[extractant], M is linear with a slope of approximately 2, indicating the association of two moles of extractant with the extracted metal species. On the other hand, the extraction decreases with an increase of the H+ ion concentration. A plot of log D vs. log[H+] gave a straight line with a negative slope of 1.7, indicating the exchange of two moles of hydrogen ions for every mole of Zr(IV). The effect of the Cl- ion concentration at a constant concentration of [H+] did not show any change in the D values. The addition of sodium salts enhanced the percentage extraction of metal, and followed the order of NaSCN > NaNO3 > Na2SO4 > NaCl. The stripping of metal from the loaded organic (L.O) with different acids indicated sulfuric acid to be the best stripping agent. An increase of the temperature during the extraction and stripping stages increases the metal transfer, showing that the process is exothermic. The synergism, regeneration and recycling capacity of Cyanex 272; the extraction behavior of associated elements, such as Hf(IV), Ti(IV), Al(III), Fe(III); and IR spectra of the extracted Zr-Cyanex 272 complex were studied.     

On the existence of pyrophosphates of tetravalent metals having a layered structure

After an accurate investigation of the thermal behaviour (TG and DTA curves) of several samples of α-Zr(HPO₄)₂·H₂O and α-Ti(HPO₄)₂·H₂O, prepared both by the refluxing and HF procedures, γ-Zr(HPO₄)₂·2 H₂O and γ-Ti(HPO₄)₂·2 H₂O, new pyrophosphate phases of tetravalent metals have been isolated.The structure of these compounds, deduced from X-ray diffraction data, density measurements and considerations of bond length and angles, arises from the packing of layers of α and γ type, identical to those present in the starting materials and held together by POP bridges.These layered M(IV)P₂O₇ are obtained after the condensation process of the HPO₄ groups present in α and γ-M(IV)(HPO₄)₂ and are stable until the transition to the respective cubic pyrophosphates takes place.The range of stability of these phases changes on going from the α to the γ phase and in part depends on the degree of crystallinity and/or the crystal size of the starting layered exchanger. The chemical implications of α- and γ-L-M(IV)P₂O₇ are examined and discussed.     

Photochemical grafting of diazonium salts on metals

4-Nitrobenzenediazonium may be photochemically grafted onto gold, copper and iron under visible and UV light. Thin nanometre layers are obtained and characterized by IRRAS, electrochemistry and ellipsometry.     

Substituent effects on carbohydrate coupling reactions promoted by insoluble silver salts

Coupling reactions were performed in the α-D-glucopyranosyl bromide series (i.e. compounds $\text{1}$ a–c, $\text{2}$ a, b, $\text{3}$ and $\text{4}$) and the α-D-mannopyranosyl bromide series (i.e. compounds $\text{7}$ a–c, $\text{8}$ a, b, $\text{9}$) with aglycons $\text{5}$ or $\text{10}$ in the presence of insoluble silver salt promotors. (i.e. silver silicate and silver zeolite). The insoluble silver salt promotes the formation of the β-glycosidic linkage, while a non-participating group is present at C-2 of the glycon. It was found that in both series 4-O-acyl functions increase the β/α ratio of the glycosidic bond formation relative to 4-O-alkyl functions, whereas 3-O and 6-O-acyl functions decrease this ratio. We assume that inductive effects are responsible for the influence exerted by 3-O-substituents, but that through-bond interactions are essential for the effects exerted by 4-O and 6-O substituents. Another unexpected finding was that coupling of α-D-mannopyranosyl bromide derivatives gave much higher β/α ratios than the corresponding reactions of α -D-glucopyranosyl bromides.     

An anion-selective membrane electrode based on a mixture of insoluble lead salts

The determination of molybdate, tungstate, perrhenate, phosphate, chromate, fluoride and hydroxide with an electrode made of a mixture of lead molybdate, tungstate and perrhenate is described. The sensitivity to the last four of these ions is interpreted in terms of their adsorption and the resultant changes in electrode surface electron density.     

Affinities of insoluble hexacyanoferrates(II) for alkali metals and ammonium

The affinities of insoluble ferrocyanides of bivalent manganese, iron and cadmium for sodium potassium, rubidium, caesium and ammonium have been studied. It has been found that the affinities of the univalent cations for the ferrocyanides generally increase in the usual order Na<K<NH₄<Rb<Cs. Comparing the results with those previously obtained, the affinity towards formation of double ferrocyanides with univalent cations generally follows the order Cd ∼ Mn >Co>Fe(II)>Ni>Zn>Cu>Fe(III). The precipitation isotherms of the systems are presented and the relationship between the affinities and some other properties of the transition metal ferrocyanides is discussed.     

Sructural parameters of the nearest surrounding of tri- and tetravalent actinide ions in aqueous solutions of actinide salts

Published data are generalized on different research methods for structural characterization of the nearest surrounding of trivalent and tetravalent actinide ions in aqueous solutions of their salts under standard conditions. The structural parameters such as coordination numbers, interparticle distances, the parameters of the second coordination sphere, and the types of ionic association are discussed. The quantitative characteristics of hydrated complexes of poorly known trivalent actinide ions are determined on the basis of comparative analysis with lanthanide ions.     

Decomposition of organic salts of some d and f metals

The thermal decomposition in non-isothermal conditions of formates, acetates, propionates and butyrates of Mn, Co, Zn, Cd, Eu, Sm and Ni was studied. The observed compensation effect allows us to calculate the isokinetic temperature. A selective activation mechanism was suggested. This leads to a good agreement between kinetic and spectroscopic data. This revised version was published online in July 2006 with corrections to the Cover Date.     

Iodometric microdetermination of some insoluble salts of silver,lead and mercury(II)

Summary An indirect iodometric method has been developed for the determination of AgCl, AgBr, AgI, PbCl₂, PbBr₂, PbI₂, PbSO₄ and HgI₂. The method does not require a prior dissolution of the sample. It is based on the exchange reaction between the insoluble salt and hydrogen sulphide, which yields a strong acid corresponding to the anion of the salt and in amount equivalent to the cation. The liberated acid is determined iodometrically. The method is simple, rapid and accurate.

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Zusammenfassung Eine indirekte jodometrische Methode zur Bestimmung von AgCl, AgBr, AgJ, PbCl₂, PbBr₂, PbJ₂, PbSO₄ und HgJ₂ wurde ausgearbeitet. Die Probe muß dazu nicht gelöst werden. Die Bestimmung beruht auf der Austauschreaktion zwischen dem unlöslichen Salz und Schwefelwasserstoff, die zur Freisetzung der dem Anion entsprechenden starken Säure in äquivalenter Menge führt. Diese wird jodometrisch titriert.

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In memoriam Professor Cecil L. Wilson.