Titration of phytic acid

Titrimetric assays for phytic acid by titration with iron(III) or thorium are described. Stannous chloride interferes in both systems, causing negative errors directly proportional to the amount of stannous chloride. The thorium:phytate ratio in the complex formed is 2:1, which is interpreted as resulting from the possession of two chelating centres by phytic acid.     

Anticosmic-shielded ultralow-background germanium detector systems for analysis of bulk environmental samples

A low-level gamma-ray counting system has been developed which reduces system background, relative to other typical low-background systems, by a factor of ten in the energy region below one MeV, and by as much as a factor of forty at higher energies. This germanium-diode gamma-ray spectrometer was constructed for a modest investment above that required for a conventional germanium detector. The techniques involved use: (1) materials of known radiopurity to surround the diode, (2) an active external anticosmic shield to reduce the background continuum due to interactions of cosmic particles with the detector and passive lead shielding, and (3) nitrogen exhausted from the cryogenic dewar to minimize the introduction of ubiquitous radon decay nuclei into the sample counting chamber. A novel method for handling samples prior to counting is presented. Also; some of the difficulties encountered in calibrating a system intended for bulk samples are discussed.Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830.     

Poly(amidoamine-organosilicon) (PAMAMOS) multi-arm star polymers

A new class of hydrophilic core – hydrophobic arms multi-arm star polymers is described: the first such materials to have silicon located in the side arms. They belong to the broad family of radially layered copolymeric amidoamine-organosilicon (PAMAMOS) dendritic macromolecules and may be viewed as nanostructured, covalently bonded, inverse micelles. Two types of hydrophobic, silicon-containing arms have been used, one based on polydimethylsiloxane (PDMS) and another based on predominantly alkyl chains attached by organosilicon chemistry to the hydrophilic polyamidoamine (PAMAM) core. The former polymers are synthesized by a reaction of amine-terminated PAMAMs by mono-functional epoxy PDMS, while the latter are obtained by haloalkylation of the same PAMAMs with a suitable unsaturated silane followed by alkylthiol addition. The Langmuir film behavior of the multi-arm star polymers with PDMS arms is described and rationalized in comparison with that of other hydrophobically modified PAMAM dendrimers reported in the literature. Their uptake of Cu²⁺ from aqueous solutions is also described.     

A tube-excited X-ray fluorescence spectrometer for use in small-diameter boreholes

A portable in-situ x-ray fluorescence analytical system that uses an x-ray tube excitation source and a cooled Si(Li) spectrometer for detecting characteristic emission x rays has been developed for use in small-diameter wells and boreholes. The 15-watt, iron-anode x-ray tube operates up to 30 kV. Three wells at the Sandia National Laboratory Chemical Waste Landfill, lined with 76 thick polyethylene, were logged specifically for Cr contamination. Detection limits below 50 ppm were achieved with counting intervals of 600 seconds and with the Si(Li) detector operating at 450-eV resolution (full width at half maximum [FWHM] for the Mn K-alpha x ray).     

THE CHEMILUMINESCENT NO—O-ATOM REACTION

Abstract— New additional experimental data were obtained to give further information pertinent to the mechanism for the chemiluminescent NO—O-atom reaction. Results were obtained for the change of emission intensities from 10 to 300 microns pressure. Some studies were also made of the effect of various third bodies. The results support a simple two body recombination for the mechanism for the light emission: NO+O + NO₂+ hv .     

The effect of cation size on ion pairing of methyl orange dye with tetraalkylammonium and benzyltrialkylammonium ions in aqueous solution

Formation constants have been measured by a solvent distribution method for the ion pairing of an arene sulfonate, methyl orange dye, with two series of quaternary ammonium ions: R₄N⁺(R=Et,n-Pr,n-Bu, andn-Pent) and C₆H₅CH₂R₃N⁺ (R=Me, Et,n-Pr,n-Bu,n-Pent, andn-Hex). Ion pairing increases dramatically as the length of the R group increases beyond butyl. Using a hard-sphere model for contact ion pairs, it is estimated that coulombic attraction contributes about –kT to the binding free energy and decreases slightly with increasing size of R₄N⁺. Other factors related to solvation effects, of which cosphere overlap predominates, contribute from –2kT to –7kT of binding energy. Plots of logK for association as a function of cation size show an inflection with decreasing slope between R=propyl and R=butyl. Possible causes for the inflection are considered.     

Electronic properties of the trimethylenemethaneiron tricarbonyl group

The substituent electronic effects of trimethylenemethaneiron tricarbonyl [TMMFe(CO)₃] have been studied, with σ values reported. Determination of these values was accomplished through three different techniques: a study of acidity relative to benzoic acid with TMMFe(CO)₃ acting as a substituent of benzoic acid; ¹⁹F-nuclear magnetic resonance (NMR) shielding analysis of m-fluorophenylTMMFe(CO)₃; and ¹³C-NMR shielding analysis of phenylTMMFe(CO)₃. The TMMFe(CO)₃ group behaves in much the same manner as a phenyl group (i.e. weakly electron releasing by resonance and weakly electron attracting by induction). The syntheses of the substituted phenyltrimethyleneiron tricarbonyl compounds are described.     

Selective Bromination of Aromatic Ethers with Pyridinium Hydrobromide Perbromide

In aqueous polar solvents, various aromatic ethers were selectively brominated using pyridinium hydrobromide perbromide.