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Powder compacted and sintered Nb2O5 pellets were cathodically polarised against graphite anode in calcium chloride melt at 1173 K to study the influence of various factors on the electrochemical reduction of the oxide. The parameters were; duration and temperature of electrolysis, open porosity of pellets, nature of anode, mode of electrolysis and configuration of the oxide cathode. The experiments were also conducted in KCl, KCl-25 mol% CaCl2 and NaCl melts to understand the effect of melt composition on the electroreduction. Different Ca–Nb–O and Nb–O intermediates were found in the pellets electrolysed for different durations of time in CaCl2 melt which eventually reduced to Nb. The current efficiency of the process decreased with increasing duration of electrolysis. Decrease in electrolysis temperature from 1173 to 1073 K led to the decrease in the rate of reduction of the oxide pellets. Pellets with high open porosity reduced faster. Carbon contamination of the melt was relatively less when pyrolytic graphite was used as anode. Of all the melts studied, the reduction was found to be better in calcium chloride melt, that too when alumina crucible was used as container of the melt.

The CaCl 2 deficient ternary eutectic melt LiCl–KCl–CaCl 2 (50.5: 44.2: 5.3 mol %) was electrochemically characterised by cyclic voltammetry and polarization techniques in the context of its probable use as the electrolyte in the electrochemical reduction of solid UO 2 to uranium metal. Tungsten (cathodic polarization) and graphite (anodic polarization) working electrodes were used in these studies carried out in the temperature range 623 K–923 K. The cathodic limit of the melt was observed to be set by the deposition of Ca 2+ ions followed by Li + ions on the tungsten electrode and the anodic limit by oxidation of chloride ions on the graphite electrode (chlorine evolution). The difference between the onset potential of deposition of Ca 2+ and Li + was found to be 0.241 V at a scan rate of 20 mV/s at 623 K and the difference decreased with increase in temperature and vanished at 923 K. Polarization measurements with stainless steel (SS) cathode and graphite anode at 673 K showed the possibility of low–energy reactions occurring on the UO 2 electrode in the melt. UO 2 pellets were cathodically polarized at 3.9 V for 25 h to test the feasibility of electro-reduction to uranium in the melt. The surface of the pellets was found reduced to U metal.

The electrochemistry of Th 4+ ions was studied in LiCl-KCl eutectic in the temperature range 698–803 K and compared with literature data. Various transient electrochemical techniques like cyclic voltammetry, chronopotentiometry, square-wave voltammetry were used to determine diffusion co-efficient of Th 4+ and apparent standard electrode potential for Th 4+ /Th electrode process. The electrode kinetics of Th 4+ /Th couple was also investigated by convolution voltammetry and impedance spectroscopy. Based on the above studies, the reversibility of Th 4+ /Th couple was addressed. The feasibility of electrochemical separation of uranium and thorium in LiCl-KCl eutectic is also discussed in this paper. It was seen that the separation of U from Th matrix was difficult in molten LiCl-KCl using a solid rod cathode and suitable reactive electrodes need to be used for efficient separation.

As part of the studies on the development of alternate extractants for fast reactor fuel reprocessing, a mixer-settler facility for performing counter-current solvent extraction runs with radioactive materials has been set up and commissioned in our laboratory for flow sheet development experiments. Mixer-settler runs were carried out with 1.1 M TiAP/Heavy Normal Paraffin (HNP) as the solvent using the above facility to test the equipment as well as the behaviour of the solvent for continuous solvent extraction processes. Stage profile data generated for the extraction and stripping of nitric acid with TiAP based solvent have been reported. Studies carried out on the continuous counter-current extraction and stripping of U(VI) for 1.1 M TiAP/HNP-U(VI)-HNO3 system under high solvent loading conditions are also reported in this paper. Overall and stage-wise mass balance data for the above runs are also discussed.

Electrochemical behavior of platinum in LiCl and LiCl-(1-3) wt% Li 2 O melts at 650 °C was studied by cyclic voltammetry in the context of its use as anode in the direct electrochemical reduction of solid uranium oxide to uranium metal. By CV measurements with graphite and platinum (anodic polarization) and tungsten (cathodic polarization) working electrodes, the decomposition potential of LiCl and electrochemical potential of the reaction Pt + 2LiCl → PtCl 2 + 2Li were determined as 3.46 V and 3.14 V respectively. Three anodic reactions viz. (i) formation of Li 2 PtO 3 , (ii) oxygen evolution and (iii) platinum dissolution were found to occur on the platinum electrode in Li 2 O containing LiCl melts. The Li 2 PtO 3 formation was found to be a fast reaction with diffusion coefficient of O 2− ions in the melt as 4.53 × 10 −7 cm 2 /s. Oxygen evolution showed very high current densities when compared to that of the surface area limiting Li 2 PtO 3 formation. The platinum electrode surface was corroded by formation of Li 2 PtO 3 when the electrode was polarized for a longer period of time in the melt. The results of the study indicated that LiCl-2 wt.% Li 2 O melt could be the optimum electrolyte composition in the electro-reduction of uranium oxide with platinum anode.

The room temperature ionic liquid, 1-butyl-3-methylimidazolium chloride (C4mimCl), was prepared and studied for the feasibility of using C4mimCl for the dissolution of uranium oxide and subsequent recovery by electrodeposition. The dissolution behavior of uranium oxides, UO3 and UO2, in C4mimCl medium by chlorination reaction was studied as a function of uranium loading, at 353 K. The electrochemical behavior of U(VI) in the resultant solution was investigated by cyclic voltammetry at tungsten electrode. The cyclic voltammogram consisted of a prominent cathodic wave occurring at the potential of −1.0 V (Vs Pt) was due to the reduction of . Controlled potential electrolysis of the solution results in a deposition of UO2. The electrodeposition of UO2 from C4mimCl medium was studied as a function of uranium loading. The results indicated that the recovery of uranium was quantitative within eight hours, when the solution obtained after the dissolution of UO3 was subjected to electrolysis. However, the recover...

Electrochemical behaviour of powder compacted and sintered Nb 2 O 5 pellet electrodes (~4 mm thick, open porosity ~10%) in molten CaCl 2 medium at 1173 K was studied using cyclic voltammetry and polarisation measurements. Similar dense Nb 2 O 5 pellets were subsequently electrolysed by using them as cathodes against graphite counter electrode in the molten CaCl 2 electrolyte medium with an aim to gain insight into the electro-reduction mechanism. The chemical changes that are taking place in the cathode and also in the electrolyte melt at different stages of electrolysis were analysed. The electro-reduction experiments were carried out at an applied voltage of 3.1 V and terminated after 2, 9, 22, 26 and 35 h of electrolysis and the visibly distinct layers present in the partially reduced samples were analysed. The analysis showed presence of Ca x Nb y O z compounds, sub-oxides of Nb like NbO 2 , NbO, etc. and metallic Nb in the samples. A pellet, which was electrolysed for 44 h was found to be reduced completely to Nb metal. The CaO, Ca and CaCO 3 produced and released to the melt during the cathodic polarisation was found to be associated with the electrochemical changes that are taking place on the electrode and this was ascertained by determination of the ‘total solubilised basicity (TSB)’ and ‘total insolubilised basicity (TIB)’ of the melt as a function of time during electrolysis. Based on the results, a three-stage mechanism comprising (i) cathodic insertion of Ca 2+ into the oxide pellet, (ii) reduction of the oxide electrode via formation and decomposition of ternary intermediates and (iii) chemical reduction of the cathode with electro-generated calcium metal has been proposed for electro-reduction of dense Nb 2 O 5 pellets.

pellets(52%TD).Therateofdeoxidationincreasedwithincreaseintheelectrolysistemperaturefrom923Kto1023K,butdecreasedonfurtherincreaseto1173K,duetosinteringofUparticlesonthesurfaceofthepellet.ThethicknessofUmetallayerincreased with increase in the applied voltage from 3.1 to 3.3 V whereas no reduction of the oxide occurred at 2.8 V. The behaviorof the graphite anode, in relation to the electro-reduction of the UO

Electro-reduction of solid UO 2 to U has been studied with molten CaCl 2 or LiCl as the electrolyte medium. Electro-reduction of thick (>3 mm), powder compacted and sintered pellets of UO 2 showed incomplete reduction resulting in a mixture of uranium metal and UO 2 . The extent of reduction of UO 2 to U was determined by employing a novel method called ‘metal estimation by hydrogen sensor (MEHS)’, in which the hydrogen evolved during the reaction of U metal in the reduced product with con. HBr was measured using an in-house developed polymer electrolyte based amperometric hydrogen sensor. The results of our investigations on incompletely reduced UO 2 pellets in both CaCl 2 and LiCl melts showed that the extent of reduction of different regions of the oxide pellet was different. It varied from 88.3% on the surface of the pellet as against 3.7% towards the centre bulk during electro-reduction in CaCl 2 (at 1173 K). The metallisation was found restricted to the surface of the pellets reduced in LiCl melt (at 923 K). Electro-reduction of small chunks of UO 2 pellet in CaCl 2 melt resulted in products with lower extent of reduction. Based on the measurements, a probable mechanism on the propagation of reduction through the solid UO 2 matrix during the electrochemical reduction process has been proposed.

Preparation of alumina and aluminium-cerium oxide microspheres was carried out by internal gelation process. The gelation behaviour of an acid deficient aluminium nitrate solution (NO3 −/AI3+ = 2.5) with hexamethylenetetramine and urea was investigated to develop a gelation field diagram. However, cerous nitrate solution formed two phase mixture, thus its gelation field diagram could not be prepared. Further, using limited composition range, smooth, crack free Al2O3 and (Al Ce) mixed oxide microspheres were prepared. The size distribution analysis of these spheres implied that the size of spheres could be controlled by changing the molarity of aluminium. XRD pattern of opaque hard spheres confirmed the presence of θ-alumina phase while that of (Al Ce) mixed oxide spheres depicted that cerium oxide containing alumina could also be obtained. FTIR spectra of the spheres illustrated the stretching mode of tetrahedral and octahedral Al-O coordination and bending mode of cerium in (Al Ce) mixed oxide spheres. S...

Room temperature ionic liquids (RTILs) are receiving increased attention for possible applications in nuclear fuel cycle. RTILs are being investigated as possible substitutes to molecular diluents in solvent extraction, and as an alternative to high temperature molten salts in non-aqueous reprocessing applications. It is well recognized that ionic liquids often display unique extraction behavior. Unusual extraction of various metal ions has been reported in literature when RTILs are used as solvent medium. These aspects make the subject of RTILs fascinating and challenging. This review provides the current status of room temperature ionic liquid research related to the extraction of actinides and fission products (cesium and strontium) from nitric acid medium, with special emphasis on the studies carried out in our laboratory.

The electrochemical behaviour of lanthanum was studied at inert tungsten electrode and reactive aluminium electrode in LiCl–KCl eutectic melt in the temperature range 698–798 K using transient electrochemical techniques. Reduction of La(III) to La(0) at the tungsten electrode takes place in a single step. The reduction shows quasi-reversible behaviour for polarization rates, 25 ≤ ν ≤ 150 mV s −1 and is predominantly controlled by charge transfer of La(III) ions for scan rates higher than 75 mV s −1 . The heterogenous rate constant of the process was estimated from impedance spectroscopy and from the semi-integrals of the cyclic voltammograms. The redox potential of the La(III)/La couple at the Al electrode was observed to be more positive than that at the inert electrode. This potential shift is due to the lowering of the activity of La in the metal phase caused by the formation of the intermetallic compound Al 11 La 3 . Thermodynamic properties such as Gibbs energy of formation of Al 11 La 3 , excess Gibbs energy and the activity coefficient of La in Al were calculated from the open circuit potential measurement.

In the recent past, room-temperature ionic liquids (RTILs) are being explored for possible applications in nuclear fuel cycle. RTILs are being studied as an alternative to the diluent, n-dodecane (n-DD), in aqueous reprocessing and as possible substitute to high-temperature molten salts in nonaqueous reprocessing applications. This paper deals with the current status of the electrochemical research aimed at the recovery of actinides and fission products using room-temperature ionic liquid as medium. The dissolution of actinide and lanthanide oxides in ionic liquid media and the electrochemical behavior of the resultant solutions are discussed in this paper.

Electrochemical redox behaviour of Ce (III) ion in LiF–CaF 2 eutectic was studied at 1093 K using tungsten (inert) and nickel (reactive) as working electrodes and platinum as quasi-reference electrode by various electrochemical transient techniques viz. cyclic voltammetry (CV), square-wave voltammetry (SQWV) and chronopotentiometry (CP). It was deduced that reduction of Ce (III) to Ce metal occurs by a single step, three-electron transfer. Diffusion coefficient ( D Ce(III) ) of Ce (III) ion was determined from CV, semi-integral analysis and CP and the values obtained were 2.2 × 10 −5 , 5.4 × 10 −5 and 3.0 × 10 −5 cm 2 s −1 , respectively. Electrochemical studies in the presence of Ni electrode showed the formation of the inter-metallic compounds CeNi 5 and Ce 2 Ni 7 , which were characterized by powder X-ray diffraction and SEM-EDAX analysis.

The anodic dissolution of U and Zr metal was studied in LiCl–KCl–UCl 3 and LiCl–KCl–ZrCl 4 , respectively, at 773 K by cyclic voltammetry and compared with their respective dissolution behaviour in blank LiCl–KCl eutectic. The anodic dissolution of U–Zr alloy in LiCl–KCl–UCl 3 was also studied at 773 K to compare with the dissolution of U and Zr. The transfer coefficients evaluated by Tafel analysis and the method of Allen–Hickling for U and Zr dissolution were found to be in fair agreement with each other. U dissolution in LiCl–KCl–UCl 3 and Zr dissolution LiCl–KCl–ZrCl 4 were also studied by chronoamperometry and the diffusion coefficient value of U 3+ was calculated to be in the range of 2.9 × 10 −5 to 3.3 × 10 −5 cm 2 s −1 which is in agreement with those reported in literature. Convolution voltammetric analysis of Zr 4+ /Zr 2+ redox couple in LiCl–KCl–ZrCl 4 was carried out for the first time to have a comprehensive understanding of the electrode kinetics.

Radiation stability of some room temperature ionic liquids (RTILs) that find useful electrochemical applications in nuclear fuel cycle has been evaluated. The ionic liquids such as protonated betaine bis(trifluoromethylsulfonyl)imide (HbetNTf 2 ), aliquat 336 (tri-n-octlymethylammonium chloride), 1-butyl-3-methylimidazolium chloride (bmimCl), 1-hexyl-3-methylimidazolium chloride (hmimCl), N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyNTf 2 ) and N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf 2 ) have been irradiated to various absorbed dose levels, up to 700 kGy. The effect of gamma radiation on these ionic liquids has been evaluated by determining the variations in the physical properties such as color, density, viscosity, refractive index and electrochemical window. The changes in density, viscosity and refractive index of these ionic liquids upon irradiation were insignificant; however, the color and electrochemical window varied significantly with increase of absorbed dose.

Lithium assisted electrochemical reduction of U3O8 in the room temperature ionic liquid (RTIL), N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf2), was studied to explore the feasibility of using RTILs for direct electrochemical reduction of uranium oxide at near ambient temperature. The electrochemical behavior of Li+ in MPPiNTf2 at stainless steel electrode was investigated by cyclic voltammetry and chronoamperometry. The cyclic voltammogram of LiNTf2 in MPPiNTf2 at 373 K consisted of a surge in cathodic current occurring at a potential of −2.8 V (vs. Fc/Fc+) due to the reduction of Li(I) to metallic form. The nucleation phenomenon observed in the voltammogram was investigated by chronoamperometry. Electrodeposition of metallic lithium on U3O8 particles contained in a stainless steel (SS) basket was carried out to examine the feasibility of reducing U3O8 to metallic form. The results are discussed in this paper.

Electrochemical behavior of trivalent lanthanides such as europium(III), samarium(III) and cerium(III) in 1-butyl-3-methylimidazolium chloride (bmimCl) was investigated by cyclic voltammetry and chronopotentiometry at platinum working electrode in the temperature range of 343–373 K. The cyclic voltammograms of these metal ions in bmimCl at Pt electrode consisted of quasi-reversible waves occurring at a cathodic peak potential of −0.769 V, −0.547 V and −0.558 V (vs. Pd, 373 K) were attributed to the reduction of Eu(III), Sm(III) and Ce(III) to their respective divalent states. A prewave observed in the cyclic voltammogram of Eu(III) represents the reduction of Eu(III) to Eu(II) adsorbed on Pt electrode. The diffusion coefficients of these trivalents in bmimCl were determined to be of the order of ∼10−8 cm2 s−1 by cyclic voltammetry and chronopotentiometry and the charge transfer rate constants (ks) were determined to be of the order of ∼10−5 cm s−1 by Nicholson method. The apparent standard potentials, E 0 * (vs. Cl2/Cl−), and some thermodynamic properties of reaction of LnCl3 from LnCl2 were determined and the results are reported in this paper.

Electrochemical studies on zirconium chloride in molten LiCl–KCl eutectic were carried out in presence and absence of Zr metal, in the temperature range 773–848 K using transient techniques such as cyclic voltammetry, square wave voltammetry, convolution voltammetry and chronopotentiometry. Two cathodic peaks due to Zr4+/Zr2+ and simultaneous reduction of Zr2+/Zr and Zr2+/Zr+ were observed in the cyclic voltammograms obtained in the absence of Zr metal. When cyclic voltammetry was carried out in presence of Zr metal, a cathodic peak corresponding to Zr+/Zr was observed which shifted to more cathodic potentials and that due to Zr4+/Zr2+ was not observed due to the disproportionation reaction involving Zr and Zr4+. However, oxidation of Zr2+ to Zr4+ was observed in the cyclic voltammograms obtained at higher temperatures. The cyclic voltammograms were complicated by the adsorption of the Zr2+ at the tungsten working electrode. A nucleation overpotential was observed in the cyclic voltammograms of LiCl–KCl–ZrCl4 in presence of Zr metal. Chronopotentiometric transients obtained in the absence of Zr metal showed two transition time plateaus corresponding to Zr4+/Zr2+ and Zr2+/Zr reductions whereas in presence of Zr metal transition time plateaus corresponding to Zr2+/Zr and Zr+/Zr reductions were also observed. Chronopotentiometry also showed that the electrode process due to Zr+/Zr was irreversible. There was no evidence of Zr3+ species in any of the cyclic voltammograms.

A task-specific ionic liquid, protonated 1-carboxy-N,N,N-trimethylmethanaminium bis(trifluoromethylsulfonyl)imide trivially known as protonated betaine bis(trifluoromethylsulfonyl)-imide ([Hbet][NTf2]) was prepared and the dissolution of uranium oxides, UO3, UO2 and U3O8 in it was studied. Dissolution of UO3 in [Hbet][NTf2] was very rapid and the saturation solubility of uranium was found to be 15 wt. % at 373 K. In contrast, dissolution of UO2 was sluggish and it was facilitated only by the oxidation of UO2 to UO2 2+. U3O8 was insoluble up to 453 K. A new procedure was developed for the individual separation of uranium oxides using [Hbet][NTf2] based on differences in solubilities. The electrochemical behavior of U(VI) in the resultant solution was investigated by cyclic voltammetry at glassy carbon working electrode at 373 K. A surge in the cathodic peak current at -0.48 V (vs . Fc/Fc+) was due to the reduction of U(VI) to U(V) and the corresponding anodic peak current was observed at a potential of 0.64 V. Increasing the potential sweeping rate increases the peak current and shifts the peak potential negatively indicating the irreversible electroreduction of U(VI) in [Hbet][NTf2]. The diffusion coefficient of U(VI) in [Hbet][NTf2] was determined to be of the order of ∼10−8 cm2/s.

Heat capacity measurements were carried out on La6UO12, Sm6UO12 and Eu6UO12 with differential scanning calorimetry in the temperature range 298–800 K. Enthalpy, entropy and Gibbs energy functions were computed. The heat capacity values of La6UO12, Sm6UO12 and Eu6UO12 at 298 K are 407, 439 and 461 J K−1 mol−1, respectively.

The electrochemical behaviour of the Ce, La and Nd oxy ions in MgCl 2 –NaCl–KCl eutectic was studied using cyclic voltammetry, chronopotentiometry, square wave voltammetry and electrochemical impedance spectroscopy. It has been deduced that the lanthanides are present as REOCl (RE = Ce, La, Nd) in the electrolyte and the reduction of oxychloride ion takes place in a single step according to the reaction REO + + 1 e - → REO ( RE = Ce, La, Nd ) The reduction of REO + was found to be reversible at lower scan rates but quasi-reversible at higher scan rates beyond 75 mV s −1 . The diffusion coefficients of the rare earth oxy ions evaluated using Berzins Delahay equation were comparable and found to be ∼10 −5 cm 2 s −1 . A single cathodic peak was observed in the square wave voltammograms at lower concentrations of the oxy ion but at higher concentrations, an additional peak was observed at a lower cathodic peak potential which is attributable to the adsorption of the product.

The electrochemical behaviour of cerium oxychloride in MgCl2–NaCl–KCl ternary eutectic was investigated by cyclic voltammetry at 823 K. The cyclic voltammogram of UO2Cl2–CeOCl in MgCl2–NaCl–KCl eutectic shows two peaks during the cathodic sweep as well as anodic sweep. The reduction of UO22+ is by a single step two-electron transfer and that of CeO+ is by a single step one-electron transfer. The reduction of CeO+ was found to be quasi-reversible. The reduction potentials of UO22+/UO2 and CeO+/CeO versus Ag(I)/Ag reference electrode at 823 K are 0.103 and −0.299 V, respectively. The diffusion coefficient of CeO+ at 823 K is in the range of (1.7–1.9) × 10−5 cm2 s−1. The cyclic voltammogram for 0.015 mol% CeOCl shows an additional peak during the anodic sweep at −0.056 V, which is being attributed to monolayer dissolution of CeO at the glassy carbon working electrode. Electrochemical impedance data of 0.015 mol% CeOCl in MgCl2–NaCl–KCl eutectic at the open circuit potential was fitted to a Randles cell from which the heterogeneous rate constant was estimated. X-ray photoelectron spectroscopy was used to confirm that the oxidation state of cerium in the eutectic is +3.

Heat capacity measurements of sodium alkoxides, namely sodium methoxide, sodium ethoxide, sodium n-propoxide and sodium iso-propoxide were carried out using differential scanning calorimetry (DSC) in the temperature range 240–550 K. From the heat capacity values, other thermodynamic functions, such as enthalpy increments, entropies and Gibbs energy functions of these compounds were derived and reported for the first time. The Cp,m 298 of sodium methoxide, sodium ethoxide, sodium n-propoxide and sodium iso-propoxide were measured and found to be 65.05, 90.87, 113.52 and 121.20 J K −1 mol −1 respectively. © 2005 Elsevier B.V. All rights reserved.

Heat capacity measurements of BaThO3 and BaCeO3 were carried out using differential scanning calorimetry in the temperature range 320–820 K. From the heat capacity values of BaThO3 and BaCeO3, other thermodynamic functions such as enthalpy increments, entropies and Gibbs energy functions of these compounds were derived.

Gibbs energies of formation of USn3, U3Sn7, USn2, and USn are determined using high temperature molten salt galvanic cells, U(s)//UCl3 in LiCl—KCl (eutectic)//U—Sn alloy.

Enthalpy increments of the title compounds are measured in the temperature range 573—1523 K for the first time by inverse drop calorimetry.

Internal gelation studies are carried out with mixed oxides of uranium and plutonium (MOX) and HMUR (i.e. mixture of hexamethylene tetramine (HMTA) and urea in 1:1 proportion). It is necessary to find surrogate of MOX for the detailed experimental work. Hence, the studies have been carried out with aluminium nitrate and magnesium nitrate. Important parameters of gelation such as temperature and concentration of precursors and the effect of sonication and drying on the gelled particles have been studied using these nitrates and HMUR. It has been found that micromixing (sonication) provides narrow and compact size distribution as compared to macromixing (using magnetic stirrer) and temperature of the precursors does not affect the size distribution of the gelled particles. The effect of drying has been studied using IR (infrared) dryer and oven dryer and it was found that IR drying augments the performance as compared to oven drying. Depending on the solubility of the gel in water and its appearance (as pasty mass which is similar to uranyl nitrate gel) aluminium nitrate is chosen as an appropriate surrogate for MOX. FTIR studies have been carried out for characterization of the gel.

In a recent paper. Cordfunke and Konings raised doubts over the reliability of our calorimetric results on the enthalpy increments of BaZrO 3 and SrZrO 3 . Our response to the comments follows

The alkaline earth fission products barium and strontium can combine with other major fission product elements such as Mo, Ce and Zr in a mixed oxide fuel pin of a fast breeder reactor to form compounds such as molybdates. cerates and zirconates. In order to understand the condition of their formation in the fuel pin basic thermodynamic data on these compounds applicable to the relevant temperature range are required. In this work enthalpy increments of BaMoO 4 , BaCeO 3 and (Ba, Sr)ZrO 3 were determined relative to room temperature using a high temperature differential calorimeter. The experimentally measured enthalpy data covered the temperature range of 985–1750 K. From these enthalpy values other thermodynamic functions such as heat capacities, entropies and free energy functions were generated using C p 298 0 and S 298 0 values of the compounds available in the literature. The free energies of formation of these compounds and the equilibrium barium partial pressures for the formation reactions have been computed in the temperature range of 500–2000 K and in the oxygen potential range of −376.56 kJ mol −1 to −502.08 kJ mol −1 .

The influence of anionic (SLS), cationic (CTAB) and nonionic (NP 9E0) surfactant micelles on the homogeneous catalytic selective hydrogenation of 2,4-hexadienoic acid to 2-hexenoic acid in alkaline aqueous solutions of pehtacyanocobaltate(III)-hydride complex was studied at 1 atm pressure and 30 C. The results indicate that, compared to the reactions in the aqueous medium, (a) surfactant micelles present in concentrations in the neighborhood of their critical micelle concentrations (CMC) enhance both the net rate of formation of the pentacyanocobaltate(III)-hydride complex and its equilibrium concentration by factors of 2 to 5 and 1.1 to 1.5, respectively; (b) the neutral NP 9E0 surfactant micelles enhance the rate of hydrogenation of 2,4-hexadienoic acid by pentacyanocobaltate(III)-hydride complex by a factor of 3, and, (c) the SLS and the CTAB surfactant micelles totally inhibit the hydrogenation of 2,4-hexadienoic acid. Probable mechanistic reasons are also advanced in order to explain the observed activation of the well known pentacyanocobaltate(III)-hydride complex by surfactant micelles.

Alkali metal salts of polyacrylic acids are water-soluble, multifunctional polyelectrolytes which exhibit a variety of solution properties useful in laundry and dishwashing detergents. This paper describes a number of studies carried out to identify the multifunctionality of polyacrylates under simulated detergent use conditions. Solution properties of several commercially available polyacrylates, with average molecular weight ranging from about 2500 to 250,000, are presented. These include: adsorption onto model particulate soil materials and fabrics, particulate soil and lime-soap dispersancy, sequestration of calcium, magnesium and ferric ions, calcium carbonate precipitation inhibition, buffer action and detergency. Where appropriate, these solution properties are compared with those of commonly used non-polymeric detergent ingredients.

Commercial detergent additives to control water hardness are of three main types, sequestrant, precipitant or ion-exchange builders. These builders lower the free hardness ion (Ca+2, Mg+2) concentration in a wash system by different mechanisms. An electrometric experimental method was used to evaluate the relative water hardness control performances of different builder-types under conditions closely simulating those of detergent’s end-use. Experimental data for the following builders are presented: EDTA, NTA, STPP, PAA, CMOS, Na-Citrate, Na2CO3 and type A zeolite. It is shown that the relative rankings of the various builders in water hardness control differ significantly with differences in use level concentration of the builder (0.005–0.100 gm per 100 ml). The application of the method to the selection of optimum molecular weight range of the newly emerging class of organic polymeric detergent builders like sodium polyacrylates (Na-PAA) (Mw=2000−220,000) also is discussed.

Oxygen potential measurements on (U,Ce)0 2−x with Ce/U + Ce ratios of 0.2 to 0.5 were carried out at 1073 and 1173 K by a gas equilibration method employing H 2 0/H 2 carrier gas. A new wet chemical method based on potentiometric titrations was used to determine and cross check the O/M ratios of the equilibrated samples. Lattice parameters of stoichiometric oxides were determined by x-ray diffraction. The oxygen potentials and their dependence on O/M and composition are discussed and compared with available literature data.

Structure X:R = H2 has been derived for the alkaloid kopsine from chemical and spectroscopic evidence and by a correlation with the alkaloid pleiocarpine (IX: R = R1 = COOCH3; R2 = H2). Structures XI: R = H2; R1 = OH; R2 = H and XI: R = H2; R1 = H; R2 = OH, respectively, represent dihydrokopsine-A and dihydrokopsine-B.

Die Experimente, die zur Ableitung der Formel I fur Kopsin, dem Hauptalkaloid aus Kopsia fruticosa, fuhrten, werden beschrieben.

Unter sehr milden Aufarbeitungsbedingungen liessen sich aus getrockneten Blattern von Kopisia fruticosa (KER.) A. DC., neben Kopsin, Fruticosin und Fruticosamin, Decarbomethoxy-kopsin und Decarbomethoxy-isokopsin isolieren. Fruticosin und Fruticosamin sind Isomere der Formel C22H24O4N2 und lassen sich gegenseitig ineinander umwandeln; das chromophore System und die Natur der funktionellen Gruppen dieser beiden Alkaloide wurden abgeklart.

In fruheren Mitteilungen wurde der Abbau von Strychnin uber 19,20-Dihydro-strychnin (11) zu 3-Hydroxy-l6β-strychindol (VI) beschrieben. VI wurde nun in (−)−16α-Strychindol((−)-VII) umgewandelt, das von den sieben Asymmetriezentren in II nurmehr deren drei mit bekannter relativer Konfiguration enthalt.

The equilibrium diagrams of the systems NaNO3–LiNO3, LiClO3–NaClO3, LiClO3–LiNO3, NaNO3–NaClO3, and NaNO3–LiNO3–LiClO3–NaClO3 have been investigated by thermal analysis and, to some extent, by X-ray powder photography. All the binary systems are of the simple eutectic type, accompanied, in one instance, by considerable solid solubility. The allotropic transformation of sodium nitrate complicates the equilibria involving sodium nitrate somewhat, especially when there is solid solution.The quaternary diagram shows that in the (fused) reaction[Formula: see text]lithium nitrate and sodium chlorate constitute the stable solid pair. The two invariant points of this system are both congruent.

A number of factors governing the polymerization of α-urease, the monomer which represents the traditional enzyme of 480,000 molecular weight, have been explicitly defined. Of major importance is mercaptoethanol (or other mercaptans), the presence of which was essential to the regular preparation of pure α-urease, and the removal of which, by gel filtration or by dialysis, regularly resulted in the formation of active polymers over the subsequent days to weeks. The polymerization proceeded several times faster at 25 ° than at 4 °, and complete separation of the trimer, the dimer, and the monomer demonstrated that the n-mers are isolable entities. The monomer and dimer so isolated also produced cross-inhibition when mixed together in assay solutions. Upon addition of mercaptan the polymers could be converted back to pure α-urease, thus demonstrating that the latter is indeed the polymerizing unit and that intermolecular disulfide bond formation is involved in polymerization. Titration of neutral urease solutions to pH 5.0 resulted in the conversion of about half the α-urease into higher polymers, which survived the return of pH to 8.5. Titration to pH 4.0 resulted in the splitting of some α-urease into active half-units (which again survived the return of pH), as well as a moderate loss in total activity. At neutral pH the polymerization of urease was concentration dependent, being roughly first order; and the kinetic pattern at 25 ° was similar to the theoretic Flory distribution for simple bifunctional condensations, compatible with the view that the enzyme polymers are linear aggregates.

The densities at different temperatures of pure molten lithium chlorate and of mixtures of lithium chlorate with lithium nitrate have been determined by a method of high precision. The change of molar volume with temperature has been interpreted in the light of possible structural changes in the melt.

The viscosities at different temperatures of pure molten lithium chlorate and of mixtures of lithium chlorate with lithium nitrate have been determined with high precision. The heats of fusion, and the molar heat capacities of both solid and liquid lithium chlorate, and of mixtures of lithium chlorate and lithium nitrate have also been determined. The heat of the transition [Formula: see text] has been obtained as the difference between the heats of solution in water of the two forms. The enthalpy, free energy, and entropy of mixing have been derived.

Fur Laurepukin-dimethylather wurde die Struktur eines 3.4-Dimethoxy-6.7-methylendioxy-aporphins (IIa) ausgeschlossen, und es konnte durch Eliminierung anderer Strukturmoglichkeiten gezeigt werden, das dem Dimethylather die Konstitution Ia zukommt.