Showing papers on "Antimony published in 1979"

Particle Analysis for the Detection of Gunshot Residue. I: Scanning Electron Microscopy/Energy Dispersive X-Ray Characterization of Hand Deposits from Firing

Abstract: Several methods of bulk elemental analysis, such as fiameless atomic absorption, flame emission spectroscopy, neutron activation analysis, and photoluminescence spectroscopy, can reliably and quantitatively determine the amounts of antimony and barium (antimony and lead in the case of photoluminescence) removed from the hand. The information thus furnished, however, in most cases is not sufficient to constitute presumptive evidence of the presence of gunshot residue. Many analyses are inconclusive because the amounts of antimony and barium (lead) are less than certain “thresholds” considered necessary because these elements are not unique to gunshot residue. Firings from .22 caliber weapons, unless the cartridge is known to be a Federal brand, are not usually analyzed because domestic rimfire primers, except Federal, do not contain antimony. Understandably, there has been great interest in alternative analysis methods capable of furnishing additional information of potentially higher specificity for gunshot residue.

n‐Type Doping Techniques in Silicon Molecular Beam Epitaxy by Simultaneous Arsenic Ion Implantation and by Antimony Evaporation

Abstract: High quality silicon molecular beam epitaxial films (Si MBE) were successfully grown in an ultrahigh vacuum system with an arsenic ion (As+) source or an antimony effusion source For As+ ions at 600 eV, the sticking coefficient was >075 at growth temperatures ranging from 750° to 950°C, while that of evaporated antimony strongly depended on the growth temperature Excellent arsenic doping control from 1014 to high 1018 cm−3 was obtained Good antimony doping control was realized from 1014 to high 1017cm−3 for growth temperatures ranging from 1050° to 500°C, respectively By these techniques, various types of doping profiles in the epitaxial film were obtained

The effect of lead on zinc deposit structures obtained from high purity synthetic and industrial acid sulphate electrolytes

Abstract: Zinc deposits contaminated with lead were found to have characteristic morphologies and orientations which were dependent on the amount of lead present in the zinc deposits and to a lesser extent on the presence of other impurities such as antimony and glue in the deposits. Increasing lead in the zinc deposits progressively changed the orientations from (1 1 2) to (1 0 1) to (1 0 0) to finally a poorly crystalline (0 0 2) structure. The lead content of the zinc deposits was dependent on both the concentration and chemical composition of lead added to the electrolyte, the current density and also on the presence of antimony or glue in the electrolyte. A relationship was shown to exist between the effect of lead contamination on zinc deposit morphology and orientation and on the overpotentials associated with zinc electrodeposition in the presence of lead.

Evaluation of a method for determination of total antimony, arsenic and tin in foodstuffs using measurement by atomic-absorption spectrophotometry with atomisation in a silica tube using the hydride generation technique.

Abstract: A method is described for the determination of antimony, arsenic and tin in foodstuffs in which organic matter is destroyed using a wet-oxidation procedure, except for arsenic in samples of marine origin in which organic matter is destroyed by the dry-ashing technique. Each element is obtained in the highest valency state and converted into the respective normal hydride with sodium tetrahydroborate(III), prior to atomisation in a flame-heated silica tube and atomic-absorption spectrophotometric measurement. The optimum conditions for this procedure are discussed and direct and indirect interference effects are described. The accuracy of the procedure is assessed for each element, and where possible the accuracy of the method in application is considered. Standard deviations of the results for levels normally found in foodstuffs have been calculated and derived limits of detection and confidence intervals are given.

Determination of germanium, arsenic, selenium, tin and antimony in complex samples by hydride generation-microwave-induced plasma atomic-emission spectrometry

Abstract: This paper describes the utilisation of a semi-automatic hydride generation device coupled to a microwave-induced argon-helium plasma that is used with a 0.5-m monochromator for the analysis of germanium, arsenic, selenium, tin and antimony in several complex samples. Incorporated in the system are a condensation tube and a Chromosorb 102 column that are used to separate the analyte species from hydrogen evolved during the course of the generation reaction, and to separate the analytes from condensed contaminants that cause spectral background interferences.Results reported are standard recoveries and relative precision for germanium, arsenic, selenium, tin and antimony in whole blood and in enriched flour. Also reported are arsenic and antimony values for NBS orchard leaves. Results obtained on complex samples are compared with the precision obtained for aqueous standards.

Incorporation of implanted In and Sb in silicon during amorphous layer regrowth

Abstract: Annealing of indium and antimony implanted into silicon at doses sufficient to produce an amorphous layer (1014–1015 ions cm−2) has been studied using high‐energy Rutherford backscattering. Annealing of these amorphous layers followed the behavior reported for layers formed by silicon ion bombardment and has a pronounced influence on both the retention and lattice‐site location of the impurities, with marked differences between substrates of (111) and (100) orientation. Following epitaxial regrowth on both orientations at 550 °C substitutional concentrations in excess of the solid solubility were observed. Impurity redistribution was not detected at this annealing temperature nor for 940 °C annealing of (100) and (110) substrates, but migration toward the surface was observed after high‐temperature annealing of (111) material. This resulted in a loss of ∼60% of implanted In after 1 h annealing, whereas antimony accumulated behind the native thermal oxide. Impurity atoms continued to migrate after lattice ...

Process for the production of ethanol and/or acetaldehyde by reacting methanol with synthesis gas

Abstract: Ethanol and/or acetaldehyde is (are) produced by reacting methanol and synthesis gas at elevated temperature and pressure in the presenee of a catalyst consisting of (a) cobalt, (b) an iodide or a bromide and (c) a polydentate ligand wherein the donor atoms are selected from nitrogen, phosphorus, arsenic, antimony and bismuth, ethanol being the predominant product when the donor atoms are exclusively nitrogen or phosphorus, particularly phosphorus, and acetaldehyde being the major product when the donor atoms are exclusively arsenic, antimony or bismuth. A particularly effective polydentate ligand is one having the formula: (R') (R2)X-(C (R3) (R6)]n -Y(R3)(R4) (II) in which X and Y are independently nitrogen, phosphorus, arsenic, antimony or bismuth; n is an integer; (R'), (R2), (R3) and (R4) are independently saturated monovalent organic radicals containing from 1 to 20 carbon atoms. Examples of polydentate ligands which are effective in the production of ethanol are those having the formula (II) in which (R1), (R2), (R3) and (R4) are C6H5, X and Y are phosphorus and n has the value 4 to 6.

Electrical behaviour of powdered tin–antimony mixed oxide catalysts

Abstract: A series of tin + antimony mixed oxide powders, calcined at 773 K, has been studied by electrical conductivity. A continuity in the electrical behaviour is found between semiconducting SnO2 and insulating Sb2O4. Pure stannic oxide is an n-type semiconductor and its free electrons come from the first ionization of anionic vacancies whose concentration is ≈ 1018 cm–3 at 608 K under 2.13 × 104 Pa O2. The enthalpy of formation of these vacancies and the ionization energy of their 2nd electrons have been estimated. As the Sb content increases, antimony dissolves into the SnO2 structure in the 5+ state, which increases the conductivity, σ, up to a maximum corresponding to 6.1 Sb atom %. Around this value formation of the Sb2O4 phase begins. The increased conductivity of mixed oxides with high Sb content (>20 atom %), compared with that of Sb2O4, which is an insulator, is attributed to a doping effect by Sn4+ cations in Sb3+ lattice positions of Sb2O4. Comparison of how both σ and catalytic properties vary with Sb content shows that electron transfer between catalyst and adsorbed species is not the rate limiting step in propene oxidation and that the solid solution of Sb5+ in SnO2 cannot constitute the active phase for acrolein formation.

Determination of lead, bismuth, zinc, silver and antimony in steel and nickel-base alloys by atomic-absorption spectrometry using direct atomisation of solid samples in a graphite furnace

Abstract: A fast and simple method of determining lead, bismuth, zinc, silver and antimony in steel and nickel-base alloys has been developed using unmodified commercial atomic-absorption equipment. The method is based on the direct atomisation of solid metal samples in a graphite furnace. The samples can weigh between 1 and 20 mg, but test results are influenced by the shape of the samples. The matrix effects are very slight. Calibration graphs have been drawn using steel samples with known contents. Practical content ranges, e.g., lead 0.03–150 µg g–1 and bismuth 0.03–6 µg g–1, and low detection limits, down to 0.02 µg g–1, have been obtained by selecting suitable lines of analysis. The relative standard deviation (1s) is approximately 6% of the content of all elements investigated throughout the stated range of content. The time required for analysis is short, being about 6 min for a duplicate determination.

A survey of the elemental composition of alloy for dental amalgam

Abstract: Analyses of 51 alloys (conventional, 41, and high-copper, 10) currently available in Australia were made. A rapid and precise procedure was developed that relied on wet-way methods for silver and tin while copper, zinc, mercury, indium and low-level constituents, such as lead, cadmium and antimony, were determined by atomic absorption spectroscopy. The conventional alloys, with two minor exceptions, all complied with the compositional requirements of modern standards and little quantitative variations was noted when the range of the major component was compared with the values obtained in two surveys made over thirty years ago. The high-copper contained, among other factors, an average copper concentration about four times that of conventional alloys. Rather surprising were the contents of mercury, indium, and cadmium found in some of the alloys as well as the low-level concentration of lead, and in a few cases antimony. Other elements were not detected by the sensitive technique used. It is justifiable to recommend that the maximum zinc content to be permitted in zinc-free type alloys should not be greater than 0.01%, and this value was subsequently incorporated in the revised Australian standard 2110-1977: Alloy for Dental Amalgam.

Process for recovering metal values from materials containing arsenic

Abstract: An improvement in hydrometallurgical recovery of metals, i.e. copper, zinc, cadmium, germanium, indium, lead, silver, gold, antimony and bismuth from materials such as flue dust containing arsenic in which the metals are selectively separated in successive process steps for final recovery, the improvement comprising precipitating arsenic as an insoluble ferric-arsenic compound in the first processing step, carrying the insoluble arsenic compound through subsequent processing steps in which it is insoluble until the other metals have been recovered leaving the ferric-arsenic compound as the final residue which can be disposed of without violating pollution requirements or converted to soluble sodium arsenate and recovered from solution by crystallization.

Dehydrocoupling of toluene

Abstract: Toluene dehydrocoupled products are produced by heating toluene in the vapor phase with an inorganic metal/oxygen composition which functions as an oxygen carrier and has an empirical formula selected from: where M 1 is at least one element selected from silver, zinc, gallium, indium, thallium, germanium, phosphorus, arsenic, thorium, the lanthanides, Groups 1 a, 2a, 3b, 4b, and 8 of the Periodic Table of the Elements and mixtures thereof, and M 2 is an element selected from bismuth and antimony, and wherein a is 0.01 to 10, b is 0 to 10, and x is a number taken to satisfy the average valences of lead, M 1 and M 2 in the oxidation states in which they exist in the composition, with the proviso that when M 2 is bismuth, M 1 cannot be gallium or thallium; and when M 2 is antimony, M 1 cannot be indium, thallium, germanium, phosphorus, or thorium; and where M 3 is at least one element selected from zinc, germanium, thorium, the lanthanides, Groups 1a, 3b, 4b, and 8 of the Periodic Table of the Elements and mixtures thereof, and M 4 is at least one element selected from indium, silver, Group 2a of the Periodic Table of the Elements, and mixtures thereof, and wherein a is 0.01 to 10, b is 0 to 10, and x is a number taken to satisfy the average valences of bismuth, M 3 , and M 4 in the oxidation state in which they exist in the composition to yield the toluene dehydrocoupled toluene product. Alternatively, the same inorganic metal/oxygen composition can be employed as a catalyst or as a combination catalyst/oxygen carrier for the dehydrocoupling reaction when oxygen or an oxygencon- taining gas is heated with the toluene.

Catalyst and process for producing methacrylic acid

Abstract: A catalyst composition useful for the oxidation of unsaturated aldehydes, particularly the oxidation of methacrolein to produce methacrylic acid, comprises the combination of oxides of molybdenum, copper, phosphorus, antimony, and cesium and/or calcium and optionally may include one or more of the elements Ni, Zn, Ru, Rh, Pd, Pt, As, K, Rb, Sr, Ba, Cr, V, Nb, W, Mn, Re, and rare earth metals including La.

Process of preparing conductive tin dioxide powder

Abstract: A process of preparing a conductive tin dioxide powder doped with 0.001-2.0 mole % of antimony oxide by heating a mixture of stannous oxalate and an antimony compound, preferably a halide, to form tin dioxide through thermal decomposition of stannous oxalate and accomplish firing of the formed tin dioxide without causing sintering. Preferably the mixture is prepared by using a solution of an antimony halide, followed by evaporation of the solvent. This process gives a tin dioxide powder low in specific resistance for the dopant concentration, high in whiteness and small in particle size.

Flame retardant epoxy molding compound method and encapsulated device

Abstract: The high temperature stability of devices encapsulated with a flame retardant epoxy molding compound is improved by including in the encapsulant as synergistic flame retardant a halogen-containing organic compound (preferably of the reactive type) and antimony pentoxide. The encapsulant may be prepared from an epoxy, a hardener preferably of the novolac or anhydride type, a catalyst, a mold release agent, preferably a filler, preferably a colorant, preferably a coupling agent, the halogen-containing organic compound (which may be part of the resin or the hardener) and antimony pentoxide. Such encapsulants, when used to encapsulate semiconductor devices, have improved high temperature compatability compared to similar molding compounds with antimony trioxide or antimony tetraoxide.

Influence of antimony catalysts with hydroxyethoxy ligands on polyester polymerization

Abstract: The effectiveness of antimony polymerization catalysts for polyester, with varying numbers of hydroxyethoxy ligands on antimony, was studied. The ligand number, ranked in decreasing effectiveness was 5 = 3 > 2 > 1 ≫ 0. Results for this series of compounds are consistent with a mechanism in which antimony bonds with polyester chain ends to catalyze intermolecular condensation.

Preparation and characterization of tetrafluorophosphonium(V) hexadecafluorotriantimonate(V), [PF4][Sb3F16], the adduct arsenic pentafluoride–trifluorophosphine (1/1), and the redox reactions of trifluorophosphine with arsenic, antimony, and bismuth pentafluoride

Abstract: Phosphorus pentafluoride and SbF5 form a 1 : 3 adduct the vibrational spectrum of which is consistent with the formulation [PF4][Sb3F16]. The 1 : 1 donor–acceptor adduct formed at –130 °C between PF3 and AsF6 has been characterized by Raman spectroscopy. The adduct is in equilibrium with its dissociated components between –130 and –78 °C; however, a redox reaction occurs at –78 °C. Phosphorus trifluoride also undergoes redox reactions with antimony and bismuth pentafluorides.

Study of the oxidative reactions of butenes over mixed tin–antimony oxides

Abstract: Primary selectivities and specific activities for partial oxidation of butene isomers over a range of mixed tin–antimony oxides of varying bulk and surface composition have been obtained using a tubular reactor operating in the differential mode. Reaction rate and product distribution vary with antimony to tin content of the catalyst and with calcination temperature. Reaction mechanisms containing positively charged allylic and vinylic intermediates, operating at specific acid–base and acid surface centres, explain the product distributions of the butene isomers. Reaction rate varies with content of surface antimony associated with the rutile structure and decreases on formation of antimony oxide phases. The influence of catalyst structure and surface composition on determining catalytic and acid–base properties is elucidated.

Molybdenum-promoted antimony phosphate oxide complex catalysts also containing at least one of bismuth and tellurium

Abstract: Molybdenum-promoted antimony phosphates also containing at least one of tellurium and bismuth have been found to exhibit significant catalytic activity in various oxidation-type reactions.