Harmon L. Finston

Further studies of the rate affected synergic solvent extraction of Fe(III)-TTA—I: The effect of tri-n-octylphosphine oxide on the solvent extraction of iron(III) with 2-thenoyltrifluoroacetone

Abstract The extraction of iron(III) from aqueous perchloroc acid into a solution of 2-thenoyltrifluoroacetone (TTA) in benzene is known to be very slow. The system does not reach equilibrium within a practical contact time of the two phases. The rate and percent of iron(III) extraction was found to increase considerably upon the addition of tributyl phosphate (TBP). An increase in temperature of 10°C results in further increase in the rate and percent of iron(III) extraction by a factor of 1·5. From the results of detailed investigation, the reason for this effect is considered to be the replacement of a slow step (the direct formation of the iron(III)-TTA complex in the aqueous phase) by a series of fast reactions (the formation of an iron(III) TBP complex in the aqueous phase, the extraction of the iron-(III)-TBP complex to the organic phase, and the replacement of TBP by TTA in the organic phase). All the observations in this system are readily explained by the previously demonstrated kinetic effect.

Quantitative analysis by proton-induced X-ray emission utilizing an inexpensive external-beam system

Abstract We describe a sensitive and convenient system for PIXE analysis in which an external beam impinges on samples in a helium-filled target chamber. Samples are presented to the beam by an ordinary slide projector, slightly modified, which can accommodate 80 slides. The numerous advantages of the system are enumerated. The sensitivity and range of detectable elements are the same as for PIXE systems employing the more usual vacuum chamber; absorption of low-energy X-rays in the helium is insignificant compared to absorption in the beryllium window of standard Si(Li) detectors.

The effect of SCN− on the extraction of Fe(III)-TTA☆

Abstract The extraction of iron from perchloric acid solution into TTA-benzene is known to be very slow and does not reach equilibrium within a practical contact time of the two phases. The addition of thiocyanate was found to enhance the rate considerably. From the results of detailed investigation, the reason for this effect is considered to be the replacement of a slow step, the direct formation of Fe-TTA complex, by a series of fast reactions, i.e. the formation of Fe-SCN complex in aqueous phase, followed by its extraction into the organic phase and the replacement of SCN − in the complex with TTA in the organic phase. The possibility for a synergistic effect based on this phenomenon is suggested.

Street level versus rooftop sampling: Carbon monoxide and aerosol in New York city

Abstract Aerosol samples were simultaneously collected with three cascade impactors for 2-h periods; two of the impactors were located at street level and the third was located on the 16th floor, all on the same city block in Manhattan. Carbon monoxide was also measured at all three sites. Particle-size distributions of the respective elements were similar, in contrast with the concentrations, which were not. The concentrations at street level, e.g. lead and CO, decreased with height as expected. On the other hand, the concentrations of particulate sulfur did not diminish with height. The results obtained from the two cascade impactors and CO monitors located around the corner from each other at street level show significantly different pollutant concentrations, thereby indicating the difficulty in obtaining representative samples at street level.

A rate promoted synergistic effect on the solvent extraction system Fe(III)-TTA-SCN☆

The promotion of the extraction rate of iron by TTA-benzene in the presence of ammonium thiocyanate was previously attributed to the rapid extraction of Fe(SCN)3 and the subsequent replacement of SCN− by TTA− in the organic phase. The replacement of the benzene solvent by a benzene-hexone mixture was found to yield both an even greater enhancement of the extraction rate and a definite synergism. It was confirmed that these effects are attributable to the mechanism previously proposed.

PIXE studies using a target chamber with helium atmosphere

Abstract The use of a helium atmosphere in the target chamber has advantages which will be discussed. The sensitivity of the system and some recent results will be discussed.

Sulfur in aerosol versus wind direction in New York City and a nearby rural site

Abstract Analysis of aerosol samples collected simultaneously in New York City and in a rural area in New Jersey showed that concentrations of sulfur were similar at both locations. Summer measurements in New York City, five months later, showed that sulfur in aerosol was as much as ten times greater when the wind blew from the southwest quarter compared to other wind directions. We infer from these results that the bulk of particulate sulfur in New York City is transport from the west.

Activation of Tl, Pb and Bi by 10–160 MeV neutrons: Possible application to the analysis of Bi+

The medium energy intense neutrons (MEIN) available at the Brookhaven Chemistry Linac Irradiation Facility have an energy distribution up to ∼160 MeV an effective neutron flux of ∼1.3×1011 cm−2s−1. The present work explores the feasibility of using this facility for the analysis of Tl, Pb and Bi by activation with MEIN. The most sensitive reactions, from a practical standpoint, were found to be Tl (n, xn)200Tl (x=4, 6), Pb (n, xn)204mPb (x=0, 3, 4. 5) and209Bi (n, 6n)204Bi. The absolute sensitivities attainable with these reactions are 0.1, 0.05 and 0.08 μg of Tl, Pb and Bi respectively, for 1 h irradiation at 1.3×1011 n cm−2s−1 with samples counted 2 h after the end of irradiation. The advantages of the method over thermal neutron activation analysis are that all three elements can be assayed at the sub-microgram concentration levels by γ-spectrometry with the help of a simple radiochemical purification and the analytical results can be verified by cross checking via the multiple (n, xn) reaction products. However, interference from Bi in the determination of Pb and from Pb and Bi in the determination of Tl limits its usefulness to the analysis of Bi.

Chemical analysis with a low energy particle accelerator

The low energy particle accelerator at Brooklyn College is being applied to chemical analysis by studies of: charged particle induced nuclear reactions, proton induced X-ray emission, and inelastic neutron scattering. Fluorine-containing gaseous compounds in the atmosphere and fluorine in airborne particulates will be determined by detection of the prompt gamma-rays and/or alpha particles emitted in the reaction19F(p,a)16O. The PIXE technique is being applied to analysis of a variety of environmental samples, and activation by inelastic neutron scattering is being investigated for elements which are not amenable to thermal neutron activation.

PIXE as an Analytical Tool: An External-Beam System in Helium and the Role of Sample Preparation

A PIXE system in which samples in a helium-filled target chamber are irradiated by an external proton beam is described. The system is well suited for study of a wide range of materials, some merely calling for qualitative analysis, and others requiring quantitative measurements. This variety mandates a flexible approach to sample preparation in order to obtain full sensitivity of the system. Some examples taken from our work are given.