Nitric Acid In Methanol Research Articles

N[sbnd]N bond cleavage upon reduction and protonation of phenylazophenylate coordinated to ruthenium complex

Azobenzene was fixed on a ruthenium(II) center bearing two 2,2′-bipyridine (bpy) ligands by a reaction of a carbonatoruthenium(II) complex ([RuII(η2-O2CO)(bpy)2]; [1]) in the presence of triflic acid, affording a phenylazophenylato complex of ruthenium(II) ([RuII(η2-C,N-o-C6H4N=NC6H5)(bpy)2]+; [2]+), which coordinated with a nitrogen atom of the azo group and a carbon atom at the ortho-position of the phenylate group. Reactions of [2]+ with nitric acid in methanol or nitric acid/sulfuric acid in ethanol afforded nitration derivatives, which were substituted at the 5-position of the coordinated phenylate group, [RuII(η2-C,N-o-C6H3(NO2)N=NC6H5)(bpy)2]+ ([3]+), or at the 3- and 5-positions, [RuII(η2-C,N-o-C6H2(NO2)2N=NC6H5)(bpy)2]+ ([4]+), respectively. Cleavage of the NN bond of the azo group on the ruthenium complex, [2]+, with four-electron reduction and five-proton addition occurred to yield a dianilineruthenium(II) complex (cis-[RuII(NH2C6H5)2(bpy)2]2+; [5]2+).

Two 3-amino-1H-pyrazol-2-ium salts containing organic anions, and an ortho-rhom-bic polymorph of 3-amino-1H-pyrazol-2-ium nitrate.

Co-crystallization from methanol of 3-amino-1H-pyrazole with 3,5-di-nitro-benzoic acid produces 3-amino-1H-pyrazol-2-ium 3,5-di-nitro-benzoate monohydrate, C3H6N3 +·C7H3N2O6 -·H2O, (I), while similar co-crystallization of this pyrazole with an equimolar qu-antity of fumaric acid produces bis-(3-amino-1H-pyrazol-2-ium) fumarate-fumaric acid (1/1), 2C3H6N3 +·C4H2O4 2-·C4H4O4, (II). The reaction of 3-amino-1H-pyrazole with a dilute solution of nitric acid in methanol yields a second, ortho-rhom-bic polymorph of 3-amino-1H-pyrazol-2-ium nitrate, C3H6N3 +·NO3 -, (III). In each of (I)-(III), the bond distances in the cation provide evidence for extensive delocalization of the positive charge. In each of (I) and (II), an extensive series of O-H⋯O and N-H⋯O hydrogen bonds links the components into complex sheets, while in the structure of (III), the ions are linked by multiple N-H⋯O hydrogen bonds into a three-dimensional arrangement. Comparisons are made with the structures of some related compounds.

Cloud point extraction for the determination of trace copper(II) in environmental samples using a new synthesized reagent and flame atomic absorption spectrometry

Cloud point extraction for the determination of copper(II) is proposed after the formation of a complex with sulfapyridylazo resorcinol (SPAR) and later measurement by flame atomic absorption spectrometry (FAAS) using Triton X-100 as a surfactant. The surfactant-rich phase was diluted with nitric acid in methanol, prior to FAAS measurement. Analytical parameters including pH, concentration of the chelating agent and surfactant, equilibration temperature and time were optimized. The effects of matrix ions on the recovery of copper ions were also studied. A detection limit of 1.64 μg L−1 along with an enrichment factor of 31 for Cu were achieved. The method was successfully applied to the determination of copper in tap water, stream water, rain water and a standard reference material.

Simultaneous pre-concentration of Pb and Sn in food samples and determination by atomic absorption spectrometry

A cloud point extraction (CPE) method has been developed for the pre-concentration and simultaneous determination of lead [Pb(II)] and tin [Sn(II)] using Acridine Orange as complexing reagent and mediated by nonionic surfactant (Triton X-114) by flame atomic absorption spectrometry (FAAS). The main factors affecting analytical performance of CPE have been investigated in detail. The extracted surfactant-rich phase was diluted with (1.0 mol L−1) nitric acid in methanol, prior to subjecting FAAS. The calibration graphs obtained from Pb(II) and Sn(II) were linear in the concentration ranges of 5–1,000 and 10–5,000 μg L−1 with detection limits of 1.40 and 2.86 μg L−1, respectively. The relative standard deviations for 10 replicates containing 25 μg L−1 of Pb(II) and Sn(II) were 2.15 and 2.50 %, respectively. The analytical procedure was verified by the analysis of the standard reference materials NWTMDA-61.2 (water-trace elements) and NIST SRM 1548a (typical diet). The developed method has been applied to the simultaneous determination of total Pb and Sn in canned food samples including juices, tomato paste, corn, and green pea.

Sensitive Ion‐Flotation Separation of Ag(I) Traces Using 2‐(2‐Methoxyphenyl)benzimidazole before Flame Atomic Absorption Spectrometric Determination in Water

AbstractA sensitive, reliable, and environmentally friendly method for simple separation and preconcentration of Ag(I) traces in aqueous samples is presented prior to their flame atomic absorption spectrometric determinations. At pH 7.0, Ag(I) was separated with 2‐(2‐methoxyphenyl)benzimidazole (MPBI) as a new complexing agent and floated after adding sodium dodecyl sulfate (SDS) as a foaming reagent. The floated layer was then dissolved in proper amount of concentrated nitric acid in methanol and introduced to the flame atomic absorption spectrometer (FAAS). The effects of pH, concentration of MPBI, type and amount of surfactant as the floating agent, type and amount of eluting agent, and influence of foreign ions on the recovery of the analyte ion were investigated. Also, using a nonlinear curve fitting method, the formation constant of 1.62 × 106 was obtained for Ag(I)–MPBI complex. The analytical curve was linear in the range of 1.8 × 10−7–1.7 × 10−6 mol/L for determination of Ag(I). The relative standard deviation (RSD; N = 10) corresponding to 0.7 × 10−6 mol/L of Ag(I), the limit of detection (10 blanks), and the enrichment factor were obtained as 1.7%, 2.9 × 10−8 mol/L, and 43.0, respectively. The proposed procedure was then applied successfully for determination of silver ions in different water samples.

Cloud point extraction for the preconcentration of palladium and lead in environmental samples and determination by flow injection flame atomic absorption spectrometry

An online cloud-point extraction (CPE) coupled with flow injection method is developed for the separation and preconcentration of palladium and lead from various matrices using flame atomic absorption spectrometry (FAAS). The method employs the formation of complexes of the metallic species with dimethylglyoxime, which are subsequently entrapped in the micelles of the surfactant Triton X-114, upon increase of the solution temperature to 60°C and loaded into the flow injection system at a flow rate of 4.6 mL min(-1). The surfactant rich-phase was retained in a minicolumn packed with animal wool at pH 6 and eluted with 1.0 mol L(-1) nitric acid in methanol at a flow rate of 1.1 mL min(-1) directly into the nebulizer of the FAAS. The CPE variables and flow injection conditions affecting the analytical performance of the combined methodology was studied and optimized. Under the optimized conditions for 25 mL of preconcentrated solution, the enrichment factors were 51 and 44, and the limit of detections were 1.0 and 1.4 ng mL(-1) for palladium and lead, respectively. Finally, the developed method was applied for the determination of palladium and lead in street dust, soil, radiology waste, catalytic converter, and urban aerosol samples. Cloud-point extraction coupled with flow injection-FAAS was proposed as an effective preconcentration and separation method for Pd and Pb determination in radiology waste, road dust, soil, and urban aerosol samples. The most favorable feature of this method is its much higher selectivity, sensitivity, rapidity, good extraction efficiency, and employs the green chemistry concept, as it does not require the addition of toxic chemicals. In addition, this proposed method gives very low detection limits and good relative standard.

Determination of Trace Copper(II) in Food Samples by Flame Atomic Absorption Spectrometry After Cloud Point Extraction

A new method for the determination of trace copper(II) in food samples by Cloud Point Extraction(CPE) combined with Flame Atomic Absorption Spectrometry(FAAS) is presented and evaluated. The method is based on the fact that hydrophobic complex of copper(II) with sodium diethyldithiocarbamate (DDTC) was formed at pH 6.0 and subsequently the hydrophobic complex was extracted into surfactant-rich phase. Copper(II) in surfactant-rich phase was analyzed by FAAS after dilution the surfactant-rich phase to 0.5 mL by nitric acid in methanol(0.1 mol L -1 ). The main factors affecting CPE, such as pH, concentration of DDTC and Triton X-114, equilibrium temperature and incubation time, sample volume were investigated in detail. The effect of coexisting ions on the recovery of copper(II) was also investigated. Under the optimum conditions, the detection limit(3 �) of this method was 1.1 ng mL -1 for copper(II), and the relative standard deviation was 3.4 % (c=100 ng mL -1 , n=7). The analytical results for the certified reference tea sample(GBW07605) were in a good agreement with the certified value. The proposed method was successfully applied to determination of trace copper(II) in milk powder and mineral water with satisfactory results.

Thermochemical safety evaluation of tertiary pyridine resin for the application to multi-functional reprocessing process “Adv.-ORIENT cycle development”

As part of “Adv.-ORIENT” ( Advanced Optimization by Recycling Instructive Eleme NTs) cycle technologies, which aim to develop a new fuel cycle based on a fast reactor cycle system, the reactivity between a tertiary pyridine resin (TPR) and a methanol-nitric acid solution at elevated temperatures has been investigated in order to prevent runaway reactions. The influence of metal ions, which simulate metallic elements in nuclear spent fuels, and that of the composition of the methanol-nitric acid solution, on the thermal hazards of the mixture of TPR and the methanol-nitric acid solution has been estimated through thermal analysis and gram-scale heating experiments. Simulated high level liquid waste nitric acid solutions (SHLLW) were prepared through the addition of 28 reagents. It is reasonable to consider that metal ions have little influence on the thermal stability of the TPR-methanol-nitric acid system. However, it is likely that the possibility of thermal explosion is increased because the heat of the reaction of the TPR-methanol-SHLLW system with its precipitates is largest in all samples. It is reasonable to assume that the vigorous reactions of the TPR-methanol-nitric acid or SHLLW system would occur minimally in a closed and reflux condition even if this system were heated, because the exothermic reaction of the TPR-methanol-nitric acid or SHLLW system would be prevented by the latent heat of the evaporation of methanol-nitric acid solution.

Ion‐flotation Separation of Cd(II), Co(II) and Pb(II) Traces Using a New Ligand before Their Flame Atomic Absorption Spectrometric Determinations in Colored Hair and Dryer Agents of Paint

AbstractA simple, rapid and inexpensive method for separation and preconcentration of some traces of hazardous elements is presented prior to their flame atomic absorption spectrometric determinations. At pH 6.5; cadmium(II), cobalt(II) and lead(II) were separated simultaneously with 1,2‐bis((1H‐benzo[d]imidazol2‐yl)methoxy)benzene (BBIMB) as a new complexing agent and floated after adding sodium dodecyl sulfate (SDS) as a foaming reagent. The floated layer was then eluted by concentrated nitric acid in methanol and introduced to the flame atomic absorption spectrometer (FAAS). The effects of pH, concentration of BBIMB, type and amount of surfactant as the floating agent, type and amount of eluting agent and influence of foreign ions on the recoveries of the analyte ions were investigated. Also, by using a non‐linear curve fitting method the formation constants of Cd(II), Co(II) and Pb(II) complexes were obtained 1.02 × 106, 1.17 × 106 and 1.46 × 106, respectively. The detection limits of Cd(II), Co(II) and Pb(II) ions were 1.2, 0.7 and 0.5 μg/L, respectively. The enrichment factors were 45.0, 42.0 and 39.0 for Cd(II), Co(II) and Pb(II) ions, respectively. The proposed procedure was then successfully applied for determination of those heavy metals in colored human hair and dryer agents of paint samples.

Cloud point extraction combined with electrothermal atomic absorption spectrometry for the speciation of antimony(III) and antimony(V) in food packaging materials

A simple, sensitive method for the speciation of inorganic antimony by cloud point extraction combined with electrothermal atomic absorption spectrometry (ETAAS) is presented and evaluated. The method based on the fact that formation of a hydrophobic complex of antimony(III) with ammonium pyrrolidine dithiocarbamate (APDC) at pH 5.0 and subsequently the hydrophobic complex enter into surfactant-rich phase, whereas antimony(V) remained in aqueous solutions. Antimony(III) in surfactant-rich phase was analyzed by ETAAS after dilution by 0.2 mL nitric acid in methanol (0.1M), and antimony(V) was calculated by subtracting antimony(III) from the total antimony after reducing antimony(V) to antimony(III) by l-cysteine. The main factors affecting the cloud point extraction, such as pH, concentration of APDC and Triton X-114, equilibrium temperature and incubation time, sample volume were investigated in detail. Under the optimum conditions, the detection limit (3 sigma) of the proposed method was 0.02 ng mL(-1) for antimony(III), and the relative standard deviation was 7.8% (c=1.0 ng mL(-1), n=7). The proposed method was successfully applied to speciation of inorganic antimony in the leaching solutions of different food packaging materials with satisfactory results.

Application of Cloud Point Extraction for Copper, Nickel, Zinc and Iron Ions in Environmental Samples

AbstractA cloud point extraction procedure was presented for the preconcentration of copper, nickel, zinc and iron ions in various samples. After complexation by 2‐(6‐(1H‐benzo[d]imidazol‐2‐yl)pyridin‐2‐yl)‐1H‐benzo[d]Imidazole (BIYPYBI), analyte ions are quantitatively extracted in Triton X‐114 following centrifugation. 1.0 mol L−1 HNO3 nitric acid in methanol was added to the surfactant‐rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for BIYPYBI, Triton X‐114 and HNO3 and bath temperature, centrifuge rate and time were optimized. Detection limits for Cu2+, Fe3+, Zn2+ and Ni2+ ions was 1.4, 2.2, 1.0 and 1.9 ng mL−1, respectively. The preconcentration factors for all ions was 30, while the enrichment factor of Cu2+, Fe3+, Zn2+ and Ni2+ ions was 35, 25, 39 and 30, respectively. The proposed procedure was applied to the analysis of real samples.

Cloud point extraction for the determination of copper, nickel and cobalt ions in environmental samples by flame atomic absorption spectrometry

A cloud point extraction procedure was presented for the preconcentration of copper, nickel and cobalt ions in various samples. After complexation with methyl-2-pyridylketone oxime (MPKO) in basic medium, analyte ions are quantitatively extracted to the phase rich in Triton X-114 following centrifugation. 1.0 mol L −1 HNO 3 nitric acid in methanol was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for MPKO, Triton X-114 and HNO 3, bath temperature, centrifuge rate and time were optimized. Detection limits (3 SDb/m) of 1.6, 2.1 and 1.9 ng mL −1 for Cu 2+, Co 2+ and Ni 2+ along with preconcentration factors of 30 and for these ions and enrichment factor of 65, 58 and 67 for Cu 2+, Ni 2+ and Co 2+, respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed procedure was applied to the analysis of biological, natural and wastewater, soil and blood samples.

Rapid Chemical Separation for Bk

An anion exchange in mineral acid and methanol system was examined in view of rapid chemical separation. An elution behavior of Bk in hydrochloric acid–methanol system was obtained using Bk. An elution behavior of Bk in nitric acid–methanol system was predicted from the relationship between an elution position and an ionic radius. The separation was completed for nitric acid–methanol system and for hydrochloric–methanol system within 40 and 25 min, respectively.

Analysis of Curium Isotopes in Mixed Oxide Fuel Irradiated in Fast Reactor

Curium is one of the key elements in recycling and transmutation of minor actinides (MA) because of its high ra- diotoxicity and difficulty of transmutation. In order to make isotopic analysis of curium in heavily irradiated fuel, the isolation technique of curium was developed by adopting anion exchange chromatography in nitric acid-methanol mixed media. The technique was successfully applied to the analysis of curium in mixed oxide (MOX) fuel irradiated in the experimental fast reactor “JOYO”. The transmutation behaviors of curium in fast reactor are discussed on the basis of observed isotopic ratio of curium.

Microstructural characteristics of the eutectoid mixture Zr2Cu and Zr7Cu10

During their investigation into the phase transformations of an equiatomic ZrCu alloy, Carvalho et al. [1] found that two kinds of solid-state transformation occur: a martensitic transformation with Ms = 440± 5 K and a eutectoid reaction with TE = 985± 5 K. The equiatomic alloy has a bcc-based ordered structure (B2) which exists as a line phase above TE [2]. Below TE, the B2 structure undergoes a eutectoid decomposition to Zr7Cu10 and Zr2Cu which have orthorhombic and tetragonal structures, respectively [2]. By rapid cooling the B2 structure to below 413 K, however, the eutectoid decomposition process is suppressed and the B2 structure transforms martensitically into at least two monoclinic structures [3, 4]. The microstructural features associated with the martensitic transformation have been studied in detail by Soe et al. [5]. As for the microstructure after eutectoid decomposition, Nicholls et al. showed it possesses a fine lamellar morphology [6]. No further information is available in the literature with respect to this lamellar structure. The present paper reports the microstructural characteristics of the eutectoid mixture Zr7Cu10 and Zr2Cu examined by transmission electron microscopy (TEM). The orientation relationship between Zr7Cu10 and Zr2Cu is also reported. The equiatomic ZrCu alloy ingots were prepared from Zr (99.5 at%) and Cu (99.9%) by melting in a water-cooled copper hearth of a high-frequency induction furnace. In order to avoid oxidation of Zr and thus obtain high quality ingots, the furnace system was initially evacuated to a pressure of approximately 2× 10−3 Pa, and then refilled with high purity argon gettered by hot Ti granules prior to melting. The ingots were remelted several times to make them homogeneous. To produce a eutectoid-type microstructure at room temperature, the ingots were sealed in a silica tube, annealed at 550 ◦C for 24 h and quenched into liquid nitrogen. Afterwards, the structure of the ingots was characterized by X-ray diffractometry (XRD) at room temperature. Samples for the electron microscopy observations were electropolished in a Tenupol 2 twin-jet polisher using a solution of 15% nitric acid in methanol at−30 ◦C and a voltage of 30 V. The samples were examined in a Jeol FX4000 transmission electron microscope operating at 200 kV. Samples annealed at 550 ◦C for 24 h and subsequently liquid nitrogen quenched, consist of two phases Zr7Cu10 and Zr2Cu which are shown in the XRD pattern of Fig. 1. The ratio of Zr7Cu10 to Zr2Cu is about 2 as estimated by TEM and is consistent with the phase diagram of the Zr-Cu system [2]. These two phases adopt a lamellar morphology as illustrated in Figs 2 and 3. No martensitic phase was detected or observed by either XRD or TEM. These results indicate that the samples had undergone a complete eutectoid transformation during annealing, which is in good agreement with the reported results [1, 2, 6]. Figs 2 and 3 show two distinct microstructural features: i) regular lamellae (Fig. 2), and ii) irregular lamellae or isolated islands (Fig. 3). The regular lamellae constitute a well-developed structure with a high degree of parallelism. It is usually continuous over a large distance. The dark lamellae with an average thickness of

Separation of strontium from calcium by means of anion exchanger and alcoholic solution of nitric acid

A possibility of mutual separation of calcium and strontium on an anion-exchange column has been studied and then used in working out methods of separation of radioactive strontium from natural samples. All examinations, carried out on model systems, showed that calcium could be completely separated from strontium on the column with the anion exchanger Amberlite CG-400 using 0.25M HNO3 in methanol as eluent. The flow velocity of this eluent in the range between 1 ml/min and 5 ml/min did not influence the efficiency of separation of calcium from strontium. The increase of the concentration of nitric acid in methanol reduced the efficiency of their mutual separation and the increase of exchanger column height neutralized the influence of the increase of acid concentration. Calcium was separated from strontium in the mass concentration ratio γ(Ca2+)/γ(Sr2+) in the range between 1∶1 to 100∶1. This separation procedure may be used for the isolation of radioactive strontium from real samples instead of using fuming nitric acid.

Determination of Total Tin and Tributyltin in Biological Tissues

Abstract Analytical procedures have been developed for the determinations of total tin and tributyltin in biological tissues using graphite furnace atomic absorption spectrometric (GFAAS) technique. For total tin determination, the acid digested sample solution of the tissues is allowed to pass through an anion exchanger column in the chloride form in order to remove the dissolved solids and residual lipids which interfere with the GFAAS measurements. Tin chloride is recovered in the eluate with 4M HNO3. For the measurements of tributyltin, the acid-homogenised tissue solution is extracted directly with n-pentane. Dibutyl- and monobutyltin and inorganic tin are removed by back-wash with 0.8M NaOH. The extract is further cleaned up by passing through a C18 solid phase extraction (SPE) tube. Tributyltin recovered in a methanol-nitric acid mixture is determined by GFAAS using tungstate-treated graphite tube. The method developed has been applied for the analysis of bivalve samples and a detection limit of 0....

Effect of Cr on the ordering behavior and ductility of an Ni-Ni4Mo alloy

Two approaches have been identified to improve the ductility of polycrystalline intermctallic compounds depending upon the embrittlement mechanism. Microalloying involving small additions of B has been proved effective in those cases where the embrittlement is associated with intrinsic weak cohesion along grain boundaries, as in the case of intermetallics based upon the L! ~ superlattice, such as Ni3AI m and Ni3Si. m Macroalloying is used when the embrittlement is caused by a restricted number of slip systems imposed by the crystal structure. For example, the crystal structure of Co3V could be changed from hexagonal (low ductility) into cubic (high ductility) by substituting Ni and Fe for some Co. TM In contrast to the cases of Ni3A1 and Co,V, most evidence points out that the embrittlement of Ni-Ni4Mo alloys is caused by a discontinuous grain boundary reaction. 14'~'61 Such a reaction can be described in terms of strain-induced recrystallization to minimize the strain energy associated with matrix ordering. 17'~} It is the objective of this communication to demonstrate that macroalloying involving an addition of Cr to a Ni-27Mo alloy which otherwise orders to Ni4Mo stabilizes a PhMo-type superlattice, producing about the same level of strengthening as with NiaMo ordering but with considerably improved ductility. Alloys examined included Ni-27Mo and Ni-27Mo-5Cr in all weight percent. Table 1 summarizes their chemical compositions. At the hypostoichiometric Ni-27Mo composition, Ni4Mo (tetragonal, D I , superlattice) precipitates from the parent face-centered cubic (fcc) lattice. Both alloys were prepared by vacuum melting and then processed into 1.5-mm-thick sheets by hotand coldrolling. Experimental specimens were solution annealed for 15 minutes at 1065 ~ in argon atmosphere and then water quenched. To examine the ordering behavior of the two alloys, annealed specimens were exposed at 700 ~ for up to 1000 hours. Mechanical properties were determined from roomand elevated-temperature tensile tests (50.8-ram gage length). Transmission electron microscopy (TEM) was used to characterize the ordered microstructure. Thin-foil specimens were prepared by the jet polishing technique in a solution consisting of 30 pet nitric acid in methanol at about 2 0 ~ Fractography was conducted in a scanning electron microscope. Both alloys were found to contain short-range order in the as-quenched condition, as was evidenced from the observation of {I I / 2 0} diffuse intensity maxima in

Evaluation of methods for the radiometric measurement of americium-241 in environmental samples

The presence of substantial amounts of manganese in a series of soil samples (about 7000 p.p.m.) led to the failure of an established method for the determination of 241Am in soils and environmental samples. A review of alternative approaches led to the development and optimisation of a more robust technique. After acid dissolution, solvent extraction of iron and anion-exchange separation of plutonium isotopes, manganese is removed by cation exchange. Rare earth elements and americium are coprecipitated on Fe(OH)3, separated by anion exchange in nitric acid-methanol and the remaining impurities removed by anion exchange in nitric acid. Chemical yields are greatly improved and analysis of reference materials gives satisfactory results.

Microstructures and Precipitation in a Rapidly Solidified Copper-Beryllium Alloy

A study of direct strip cast copper-beryllium alloys is of interest to determine if enhanced properties could be obtained from rapidly solidified material compared to those of conventionally processed material. The present investigation was undertaken to characterize the as-cast microstructure of this material and to study the metastable phases which formed in this alloy as a result of precipitation from the rapidly quenched condition.The melt spinning technique was used to produce ribbons of a copper-beryllium alloy of nominal composition Cu-1.90wt% Be containing 0.25 wt% cobalt. The as-cast ribbon was approximately 0.1 mm thick and 12 mm wide. The Metglas Products Division of Allied Corporation provided the material. As-cast specimens were salt bath aged at 370 C for 5 min or 3 hours. Thin foils for transmission electron microscopy (TEM) were prepared from the melt spun ribbons by electrolytically thinning in a twin-jet electropolisher using a solution of 30% nitric acid in methanol at -30 C and 25 volts. The specimens were examined in a Siemens 102 transmission electron microscope operating at 125 kV.