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Europium(III) and terbium(III) complexes have been prepared using the ligands 2-(4,5-dihydro-1,3-oxazol-2-yl)phenol (HL1) and 2-(4,5-dihydro-1,3-thiazol-2-yl)phenol (HL2) in yields ranging between 74 and 100 %. Metal-to-ligand ratios of 1:3 and 1:4 can be achieved, giving rise to compounds with the formulae [Ln2(L)6] and NR4[Ln(L)4], Ln = Eu, Tb. Recrystallisation of the complexes from DMSO resulted in the formation of octanuclear complexes [Na2(Ln(L1)3)2(CO3)(DMSO)2]2 held tightly together by carbonate ions that have been formed from CO2 from the atmosphere. Five structures have been determined, showing a bidentate binding mode of the ligand through the phenolate oxygen and the nitrogen atom of the five-membered ring. Most terbium compounds show bright luminescence upon excitation with near-UV radiation, with quantum yields of 16 % to 79 %. Strong emission is observed for NBu4[Eu(L1)4] and NEt4[Eu(L2)4] with quantum yields of 43 % and 20 %, respectively.

The stability constants of some lanthanide-α-hydroxyisobutyrate complex systems have been determined by cation exchange measurements. Fronaeus' method was used to calculate the consecutive formation constants of the terbium and thulium complex systems in 0.2 M and 1 M ammonium perchlorate. The β3 values of nine lanthanide complex systems have been derived by Schubert's method. The formation constants determined by the cation exchange technique agree with the values found by potentiometric titration.

The complexation between bivalent metal ions and itaconate was investigated potentiometrically at unit ionic strength in NaClO4 at 25.00±0.01°C in the pH region 2-4.5. The complexes ML, ML2, MHL, MHL2 and MH2L2 can be identified and their stability constants calculated by both a graphical and a computer method. The results are in a good agreement with those obtained from polarographic measurements.

In order to compare α-hydroxyisobutyrate and atrolactate as complexing eluants for the separation of lanthanide ions on cation exchange resins, the distribution constants for a number of their lanthanide complexes were determined simultaneously at 25±0.1 ° and ionic strength 0.2 with ammonium perchlorate in aqueous solution. Column techniques were used to compare the HETP of the Tb-complex with each ligand. Finally a comparative test separation was carried out on a mixture of lanthanide ions. In view of the results atrolactate should not be considered as a promising alternative for α-hydroxyisobutyrate as it offers only little improvement.

The four successive stability constants and their standard deviations have been determined for the α-hydroxy-isobutyrate and lactate complexes of the lanthanide elements and yttrium. A least squares treatment of the experimental data obtained by the Calvin-Bjerrum potentiometric titration method using an I.B.M. 1620 high speed digital computer is described.

The validity of Nernst's law (equation 1), was studied for some reversible oxidation-reduction systems, with oxidation potentials situated at the limit of, or outside the stability range of water. The Ce+4-Ce+3 system in H2S04 0,5 N (E0 = 1,444 V) and in HClO4 1 N (E0 = 1,694 V) was studied and also the Co+3-Co+2 system in H2SO4 1 N (E0 = 1,81 V). It was shown that Nernst's law is valid, but that in some cases there occurs a decreasing of the experimentally measured potentials in regard to the reversible oxidation-reduction potentials (ENernst > Emeasured). These deviations are due to an anodic oxidation current of the solvent, which is added to the anodic oxidation current of the reductant (Ce+3 or Co+2). The reductions of the potential are the larger as the total concentration of oxidant and reductant becomes smaller and as the potential itself becomes higher. Under influence of the solvent, there occurs, as function of time and dilution, a reduction of the oxidant (Ce+4 or Co+3) at the same time as a decreasing of the potential. This reduction continues until an equilibrium is reached with the solvent.

Phase diagrams were constructed from phase equilibrium calculations for the quaternary system Ca(OH)2-Sr (OH)2-H3PO4-H2O and for the system Ca(OH)2-Sr(OH)2-H3PO4-HX(BOH)-H20 at 25°. On the basis of these diagrams the stability field of solid solutions of calcium and strontium hydroxyapatite was derived. The calculations show the borderlines of the apatite field to be determined by the activity isotherms of the sparingly soluble phosphates CaHPO4.2H2O, Ca8H2(PO4)6.5H2O, β-SrHPO4 or Sr6H3(PO4)5.2H2O depending on the pH and the molar cSr:cCa and cCa: cP ratios in the solution. The biological implications of these results are discussed.

The solubility of CaHPO4·2H2O and MgHPO4·3H2O is determined in the system M(OH)2-H3PO4-H2O at 37°C with M = Ca or Mg and in the range 4.1 < pH < 6.3 and 4.9 < pH < 7.2 respectively. The solubility behaviour of both solids can be described consistently only by taking into account the formation of the ion pairs MH2PO4+ and MHPO4. The thermodynamic solubility product of CaHPO4·2H2O and the thermodynamic association constants for CaH2PO4+ and CaHPO4 with their standard error are determined as (2.06 ± 0.05)×10−7 mol2/L2, 8.4 ± 1.7 L/mol and 542 ± 46 L/mol. The corresponding constants for MgHPO4·3H2O, MgH2PO4+ and MgHPO4 are (1.15 ± 0.07)×106 mol2/L2, 43.0 ± 6.7 L/mol and 1004 ± 89 L/mol.

Dielectric constants at 1.8 MHz of the propyleneglycol-water system are determined from 15 to 50°C at 5° intervals. The dielectric behaviour of the system is discussed in terms of a deviation from a linear function of the volume fraction of the components. Comparison with the monohydric alcohols and ethyleneglycol reveals the importance of the apolar/polar group ratio in the intermolecular interactions.

Refractive indices of the propyleneglycol-water system are determined from 15 to 50°C at 5°C intervals using the sodium D-line. An equation relating the refractive index to weight percent propyleneglycol and temperature is proposed. The change of the refractive index of the system deviates markedly from a linear function of the composition. The molar refraction for the mixtures is found to be nearly additive and temperature independent.

A cyclic voltammetric stripping technique is used to analyse the influence of five parameters on the copper deposition at a rotating platinum ring-disc electrode. The impact of two pretreatment methods, carbon and electrolytic, and the concentration variations of sulphuric acid, copper sulphate and chloride ions are evaluated in a factorial analysis using the Yates algorithm. Extra information is gathered by electrogravimetric and X-ray diffraction techniques. The most significant single factors are the copper sulphate and chloride ion concentrations. Carbon treatment with sulphuric acid concentration and electrolytic pretreatment with copper sulphate concentration are important hybrid factors, i. e. with mutual influence.

The solubilities of synthetic β-Ca3 (PO4)2 [TCP] and Mg-containing β-Ca3 (PO4)2 [TCMP] were determined in the system Ca(OH)2-Mg(OH)2-H3PO4-KCl-H2O at 25° C. The thermodynamic solubility product of TCP is found to be (1,14 ± 0.10) x 10−30 mol5. l−5. The incorporation of Mg2+ results in a remarkable stabilization of the β-TCP structure as reflected by a drastic decrease in the amount of solid dissolved for TCMP compared to that for TCP and by the fact that the solutions are undersaturated with respect to calciumhydroxyapatite. On the basis of solid state chemical and thermodynamical principles the solubility behaviour of TCMP solid solutions is discussed. Indications are found that magnesium whitlockite possibly precipitates during the equilibrations of TCMP.

Differential pulse polarography was used for the quantitative determination of europium in minerals and oxides of lanthanides. The reduction of europium (III) to the divalent state shows suitable polarographic characteristics in several supporting electrolytes, for which differences in sensitivity have been tabulated. Procedures have been described for the direct determination of europium (III) in lanthanide-oxides down to 0.2 ppm using 0.5 g samples. Europium was also determined in the mineral bastnaesite after a previous separation of the lanthanides by oxalate precipitation.

Differential pulse polarography was used for the quantitative determination of ytterbium(III) in minerals and oxides of other lanthanides. As the reduction occurs at fairly negative potentials and the reduction of hydrogen ions interferes at low pH the number of suitable supporting electrolytes is limited. At pH > 6 hydrolysis effects cause the reduction peak current to decrease as a function of time. Down to 5.10−-8 M ytterbium(III) can be determined in the supporting electrolyte LiCl (0.1 – 1 M) at pH 5. The analysis of ytterbium(III) in commercial samples showed average relative standard deviations which do not exceed 7%.

Two different methods for the polarographic determination of Co in steel have been examined. The first one is based on the reduction Co+3 to Co+2 after oxydation of the Co+2 by PbO2 in the presence of EDTA. Interfering elements are precipitated with pyridine. The other is based on the reduction Co+2 to Co, after the separation of Co+2 from all interfering elements by extraction of the complex ion Co(SCN)4−2 with hexylalcohol-ether mixture, followed by extraction of the alcoholic phase with NH3 and destruction of the rhodanide by heating with strong nitric acid. Iron and chromium are previously separated. Both methods give very satisfactory results.

The voltammetric behaviour of Bi(III)/Bi(Hg) in 4M HClO4 has been studied with the aid of DC polarography and cyclic voltammetry. The reduction mechanism is complex. The electrochemical reduction is preceded by a homogeneous chemical reaction and the three-electron reaction has to be considered as three successive one-electron transfers. Quantitative results relative to as well the electrochemical as the chemical reaction are obtained.

The standard emf of the cell Pt;H2/HCl(solvent)/AgCl, Ag |1| is reported for the mixtures 80, 90, 95 and 98 wt-% 2-methoxyethanol and respectively 20, 10, May and February wt-% water. The correlation of the present and previous results enables to present a structure for solutions of hydrogen chloride in mixtures of 2-methoxyethanol and water.

The reversible oxidation-reduction system Fe+3 — Fe+2 was investigated in connection with the validity of Nernst's law (equat. 2). The study was based on the results of three separate measuring methods: the measuring of the potentials, the study of polarograms and analytical determinations—colorimetric or volumetric—of the ratio of Fe+3/Fe+2 which is really present in the solution. It could be shown that in so-called pure Fe+3 or Fe+2 solutions, where Charlot-Bezier talk of mixed-potentials, the potential is in fact determined by the ratio of Fe+3/Fe+2. When diluting strongly (10−5-10−6 M), the potential is also determined by this ratio and no indefinite potentials occur. In some cases (measurements in H3PO4) an increase may occur of the oxidation potential measured in regard to the reversible oxidation-reduction potential. (ENernst < Ecalculated). These deviations are due to the cathodic reduction current of the solvent (especially of the dissolved oxygen) which is added to the cathodic reduction current of the oxidant Fe+3. They increase more and more as the concentration of Fe+3/Fe+2 becomes smaller or as the potential of the solution is lower. Under influence of the solvent there occurs either oxidation of Fe+2 with an increase of the potential or the reduction of Fe+3 with a decrease of the potential, as function of time and dilution. This oxidation or reduction continues until an equilibrium is obtained with the solvent.

The spectrophotometric determination of traces of Ce4+ and Ti3+ in the presence of respectively large excesses of Ce3+ (≤ 10–1 M) and Ti4+ (≤ 10−1 M), is described. Indirect methods are elaborated for both ions. The reaction of Ce4+ with an excess of Fe2+ gives an equivalent amount of Fe3+ which can be determined with thiocyanate. The determination of the not reacted Fe2+ with o-phenanthroline is also possible. The reaction of Ti3+ with an excess of Fe3+ gives an equivalent amount of Fe2+ which can be determined with o-phenanthroline.

Oxidation-reduction potentials of solutions of Ti+4 and Ti+3 have been determined as a function of time and dilution. It follows from this study that the equation of Nernst can be applied and that deviations which occur for more dilute solutions are due to the influence of the cathodic reduction current of the solvent, as is shown from the polarization curves. As the anodic oxidation of the reductant (Ti+3) occurs at more negative potentials than the cathodic reduction of the solvent, oxidation of Ti+3 cannot be avoided even in a nitrogen atmosphere. In solution all Ti+3 is eventually oxidized to Ti+4.

Previous studies have not demonstrated consistent results on the effect of surgical delay on outcome. This study investigated the association between the delay to surgery and the development of postoperative complications, length of hospital stay (LOS) and one-year mortality. Patients that underwent surgery for a hip fracture in a two-year period were included in a retrospective study. Uni- and multivariate regression analysis was performed in 192 hip fracture patients. There was a trend towards fewer postoperative complications (P = 0.064; multivariate regression, MR) and shorter LOS (P = 0.088; MR) in patients with a delay of less than one day to surgery. No association between surgical delay and one-year mortality was found in the population as a whole (P = 0.632; univariate regression, UR). Delay to surgery beyond one day was associated with an increased risk of infectious complications (P = 0.004; MR). In ASA I and II class patients, operation beyond one day from admission was associated with an increased risk of one-year mortality (P = 0.03; MR) and more postoperative infectious complications (P = 0.02; MR). The trends towards fewer complications and shorter LOS suggest that early surgery (within one day from admission) is beneficial for hip fracture patients who are able to undergo an operation.

Tungsten films are deposited by metal-organic chemical vapour deposition in a vertical hot-wall thermobalance reactor and a cold-wall stagnant flow reactor from Cp 2 WH 2 ( Cp ≡ cyclopentadienyl ) and CpW(CO) 3 CH 3 . Vapour pressure measurements show low volatilities: 13 mTorr for Cp 2 WH 2 and 89 mTorr for CpW(CO) 3 CH 3 at 75°C. Measurements of growth rate vs. reciprocal substrate temperatures reveal a kinetically limited deposition up to relatively high temperatures (400–500°C), with low growth rates. At 400°C, growth rates are approximately 5 nm h −1 with Cp 2 WH 2 and approximately 0.16 μm h −1 using CpW(CO) 3 CH 3 . The tungsten layers contain 5–15at.% C and 5–10at.% O.

Food irradiation is the process of exposing food to ionising radiation in order to disinfect, sanitise, sterilise and preserve food or to provide insect disinfestation. Irradiated food should be adequately labelled according to international and national guidelines. In many countries, there are furthermore restrictions to the product-specific maximal dose that can be administered. Therefore, there is a need for methods that allow detection of irradiated food, as well as for methods that provide a reliable dose estimate. In recent years, the comet assay was proposed as a simple, rapid and inexpensive method to fulfil these goals, but further research is required to explore the full potential of this method. In this paper we describe the use of an automated image analysing system to measure DNA comets which allow the discrimination between irradiated and non-irradiated food as well as the set-up of standard dose-response curves, and hence a sufficiently accurate dose estimation.

A series of titanium compounds, Ti(NMe 2 ) 4 , t-BuTi(NMe 2 ) 3 , [Ti(μ-N-t-Bu)(-NMe 2 ) 2 ] 2 , Ti(t-BuDAD) 2 and CpTi 7 H 7 , have been screened in combination with NH 3 for their suitability as precursors for the CVD of titanium nitride films at substrate temperatures of 300-600 o C and a system pressure of 1.5 Torr. The best TiN layers have been grown using t-BuTi(NMe 2 ), and NH 3 , from which an 0.8 μm thick layer deposited at 400 o C, showed a resistivity of 1.4-10 -3 Ω-cm and contained 5 atom% carbon and 6 atom% oxygen

Shortly after exchange transfusions (n = 7) with citrate-dextrose-phosphate (CDP)-treated blood, but not after regular transfusions (n = 9), sodium concentrations in plasma were significantly and paradoxically lower (3-10 mmol/L) by Ektachem 700 XR determination [with use of electrolyte reference fluid (ERF) generation 00] than by flame photometry. Similar between-method differences could also be generated by in vitro supplementation of plasma pools with CDP solution, with trisodium citrate, or to a lesser extent with Na2HPO4. For four potentiometric methods the analytical recovery of sodium added as CDP was significantly lower than by flame photometry. Within each potentiometric method the recovery was also less than the value for sodium added as NaCl. A significant association of sodium ions with citrate3- ions and, to a lesser extent, HPO4(2-) ions could theoretically account for at least part of the observations, conferring greater medical relevance to potentiometric measurements in this particular clinical situation.

Thiocyanate (previous designation rhodanide, SCN-) is a physiological substance which is ubiquitously spread in the animate nature. As an essential constituent of cell it participates in important physiological resp. biochemical processes. From the hygienic and microbiological point of view the occurrence of SCN- as environmental factor, its alimentary significance and its vitalizing effect (stimulation of nonspecific and specific warding off, stimulation of proliferation, protective effect at toxic loading) are of interest for the fundamental and applied research.

Conductivity measurements at 25°C, on solutions of hydrogen chloride in various mixtures of 2-methoxyethanol and water, are reported. The experimental data were analysed by means of the Fuoss-Onsager equation. The limiting equivalent conductivity and the association constant were determined. This study focusses on the effect of the decreasing amount of water in the solvent mixture, on the ion-solvent interactions and discusses aspects of the solvation and the structure of the electrolytic solutions.

The reduction of Yb(III) to Yb(II) in 1 M NaClO 4 in the pH range 1.9–6.6 was studied by d c. polarography, cyclic voltammetry and electrode impedance measurements as a function of frequency and electrode potential. It results that the d.c. reversible reduction is followed by a homogeneous chemical reaction and is accompanied, by an irreversible process which is attributed to a lowering of the overpotential of the reduction of the hydrogen ions. Values of the rate constant and transfer coefficient pertaining to the charge transfer step were deter mined.

The solubility of antimony in mercury has been studied by cyclic and stripping voltammetry in solutions of Sb(III) in 4 M HCl. The solubility has been evaluated at 8.57×10−4 mol l−1 or 1.27×10−3 at. % at 25°C which agrees well with solubility values derived from data reported by other authors at different temperatures. A solubility heat (Hsol) of 16.7 kJ mol−1 was calculated.

A dc polarographic and cyclic voltammetric study has been made of the reduction of Sb(III) ions from 4 M HCl, 1 M HCl + 3 M HClO 4 and 0.1 M HCl + 3.9 M HClO 4 solutions. Reversible behaviour was observed, accompanied by significant specific adsorption of Sb(III) ions on the mercury electrode. Double potential step chronocoulometry was employed to determine the extent of adsorption which correlates better with the amount of adsorbed Cl − ions than with the potential or electronic charge of the electrode. From this correlation and the distribution of the complex species in solution it is concluded that SbCl 3 or SbCl 4 − is the adsorbing species.

The reduction of Hg(II) at a glassy-carbon electrode in various electrolytes has been studied by rotating ring-disc voltammetry. Reduction proceeds directly to metallic mercury in a single 2-electron step. However, at the foot of the wave, and only during the first reduction sweep after pretreatment of the electrode surface, a small amount of Hg(I) species is detected at the ring. The appearance of an Hg(I) intermediate is most pronounced in sulphuric acid solution. The reduction of Hg(II) is found to proceed irreversibly and to be of first order. At sufficiently negative potentials the reduction is convective-diffusion controlled. Stripping voltammetric experiments indicate that the dissolution of mercury gives Hg(II) in complexing electrolytes. In non-complexing electrolytes the initially formed Hg(II) reacts with mercury atoms on the electrode surface to give Hg(I). During electrodissolution, two stripping peaks may be observed as a result of underpotential adsorption of mercury on glassy carbon. The difference in peak potential between the adsorption (mono) layer peak and the bulk mercury peak has been related to the difference in work functions of the deposit (mercury) and substrate (carbon). A rotating glassy-carbon electrode has been used for the anodic stripping determination of mercury. When an appropriate amount of a cation such as cadmium(II) or copper(II) is added to the test solution, mercury down to 2 × 10−9M (0.4 ng ml ) can be determined in acidified thiocyanate electrolyte with a relative standard deviation of about 22%.

The electrical conductance of solutions of hydrochloric acid in a mixture of 80 wt% 2-methoxy-ethanol and 20 wt% water has been studied at temperatures from 20 to 50°C. The results have been interpreted with the Fuoss Onsager theory for associated 1-1 types electrolytes. The values of the association constant K A , the limiting conductivity and the distance parameters have been computed at each temperature.

The possibilities of the silver sulfide membrane electrode for the determination of cyanide are described; determinations by multiple standard addition and titration have been studied, and interferences have been checked. The determination of cyanide in solutions containing various metal complexes, and the evolution method for separation of hydrogen cyanide are discussed. Automatic titration can be used for samples containing 1 p.p.m. cyanide, and the standard addition method for 1 p.p.b. cyanide.

A method is described for a rapid, sensitive, accurate and precise determination of 12 lanthanides and yttrium by a.a.s. In most analyses the standard addition technique was used to eliminate chemical, ionization and matrix interferences. For samples of similar origin, a procedure with a comparison standard was developed; this proved to be very suitable for routine analyses. The lanthanides and yttrium were determined in bastnasite, monazite and gadolinite. The analyses were performed on solutions containing a maximum sample concentration of 30 g l-1 in 80% of methanol and buffered with alkali ions. The accuracy of the method was checked by independent procedures such as gravimetry, pulse polarography and flame emission spectrophotometry.

A pulse-polarographic method for the simultaneous determination of traces of nickel, zinc, cobalt and manganese in cadmium and its compounds is described. Interference from the reduction of the cadmium matrix was eliminated by a prior electrolytic deposition of cadmium on a mercury cathode at a controlled potential of –0.90 V vs. S.C.E. Iron in excess interfered with the determination of cobalt and was therefore extracted from the electrolysed solutions. The polarographic determination was performed in 0.1 M lithium acetate -0.025 M lithium thiocyanate as supporting electrolyte. A sample weight of 10 g and a final volume of 10 ml allowed the determination of about 0.08 p.p.m. nickel, 0.01 p.p.m. zinc, 0.02 p.p.m. cobalt and 0.003 p.p.m manganese. Less than 0.01 p.p.m. nickel could be determined with a 0.25 M pyridine 0.05 M potassium chloride supporting electrolyte. Several synthetic samples and commercially available cadmium products were analysed.

The stability constants of the lanthanide and yttrium, complexes with α-hydroxyisobutyrate and lactate, have been determined by potentiometric titration. The average numbor of ligands bound per metal ion has been calculated by the method of calvin-wilson and indicates the formation of uninegative tetra-ligand complexes of the form ML4-. The 4 formation constants have been derived by 4 procedures; bjerrum's half-n¯;-method. fronaeus' and poulsen's extrapolation methods, and by least squares calculation, using an IBM 1620 digital computer.

Traces of antimony, copper, and lead impurities in titanium dioxide have been determined simultaneously by pulse polarography. The three metals were separated from titanium(IV) by sulphide precipitation at pH ≅3, using cadmium as carrier and complexing titanium with fluoride. The precipitation of lead was supplementary controlled with the radio-isotope 210Pb, showing a quantitative recovery. In hydrochlorid-hypophosphite supporting electrolyte, antimony, copper, and lead in titanium dioxide can be determined as low as 0.15, 0.03, and 0.1 ppm respectively. The method was applied in the analysis of various titanium dioxide products commercially available, showing satisfactory sensitivity and resolution for divergent copper-antimony ratios.

Traces of antimony, tin and arsenic in cadmium products were determined by pulse polarography. Arsenic was distilled, while antimony and tin were precipitated as hydroxides with manganese dioxide as carrier; some lead was coprecipitated with tin, hence these elements were further separated by distillation. In all cases quantitative recoveries were obtained. Antimony(III) was determined in a hydrochloric acid-sodium hypophosphite mixture, tin(IV) in a hydrochloric-hydrobromic acid mixture and arsenic(III) in sulphuric acid as supporting electrolytes; for arsenic(III), methylene blue had to be added. A sample weight of 10 g and an end volume of 10 ml allowed the determination down to about 0.004 p.p.m. antimony, 0.006 p.p.m. tin and 0.003 p.p.m. arsenic in cadmium. Several synthetic samples and commercially available cadmium products were analysed.

Summary A pulse polarographic method for determining traces of zinc and managanese in cobalt and its compounds is described. Interference due to the reduction of the cobalt matrix was eliminated by a prior separation on an anion exchange resin. The yield was controlled with the radio-isotopes, 65Zn and 54Mn, and a quantitative recovery was obtained for both elements. After separation, zinc was determined in an acetate medium; for managanese, 0.1 M lithium chloride was chosen as supporting electrolyte. A blank value prevented the attainment of the pulse polarographic detection limit for zinc and manganese, being about 10−8 M for both elements. The method enables as little as 0.15 p.p.m. of zinc and 0.03 p.p.m. of manganese to be determined in a 1 g sample. A number of analyses carried out on synthetic and various commercially available cobalt samples showed satisfactory sensitivity and accuracy.