A close relation between thermal data and the thermodynamic stability of intermetallic compounds is pointed out. Several series of intermediate phases formed by metals of theA and transition groups with elements of groups IB to IVB have been considered. The dependence of the thermal and thermodynamic stabilities on the atomic size, the electronic configuration, the electronegativity and the melting temperature of the component is discussed.
Authors:V. Garcia, P. Colonna, D. Lourdin, A. Buleon, H. Bizot, and M. Ollivon
Order-disorder transitions were investigated in native cassava starch at intermediate moisture contents (35 to 60% wt. water), using Differential Scanning Calorimetry (DSC) and dynamic Wide Angle X-ray Diffractometry (WAXS) with a synchrotron radiation source.
Authors:D. Gilliland, G. Basmadjian, A. Marchand, G. Hinkle, A. Earlywine, and R. Ice
A simple, one-step micro-synthesis of aromatic radioiodides which utilizes the in-situ formation of arylthallium bis (trifluoroacetate)
intermediates has been developed. Thallium(III) trifluoroacetate was used in the thallation of aryl compounds to yield the
intermediate arylthallium bis (trifluoroacetate). The latter was isolated, purified and used for radioiodination. Alternatively,
in-situ radioiodination was accomplished by the addition of radioactive aqueous NaI plus excess non-radioactive iodide to
complete the reaction. Yields of up to 81% of radiochemically pure compounds were obtained. Using the modified thallation-radioiodination
method, aromatic radiopharmaceuticals can be easily and quickly labelled with123I.
CS biopolymer for the removal of phenol and its intermediates. Both TiO 2 and CS layers were immobilized onto a glass plate which acted as the inert photo-chemical support. Phenol was chosen as the model pollutant because it is a colorless and
An intermediate neutron moderation method for measurement of moisture and/or hydrogen contents of small samples is presented.
The sample is placed on the top face of a neutron howitzer, with a cadmium sheet between. Thermal neutrons resulting from
intermediate neutron moderation in the sample are detected with a3He proportional counter placed on the sample, by a cadmium difference method. With a 500 mCi Am-Be neutron source, the limit
of moisture detection for a 10×20×1.8 cm3 asbestos plate in 1 min count time is 0.5 wt.%. The precision of measuring the hydrogen contents of 250 ml hydrocarbons containing
112 mg H/ml is 0.9% under the same conditions.
Authors:N. Foster, R. Dannals, H. Burns, and N. Heindel
Pyrrolidyl triazenes prepared by interception of the diazonium transient in the Sandmeyer reaction of amines can serve as
useful intermediates in the iodination and radioiodination of aryl rings. Decomposition of such triazenes in the presence
of iodide is acid-catalyzed and is sensitive to choice of solvent, acid, and triazene structure. A condition variation study
by HPLC of four different solvent systems and two non-nucleophilic acids was carried out on the123I iodination of the triazenes of p-nitroaniline, p-anisidine and p-toluidine. This method has proven useful in radiolabeling
of two pharmaceutical analogs which were not amenable to labeling through the classic Sandmeyer method.
Authors:A. Markowicz, N. Haselberger, H. El Hassan, and M. Sewando
Problems connected with quantitative EDXRF analysis of intermediate thickness samples are addressed. The first one is a systematic study of the various contributions to the total error of the E-T method. Special attention is also given to the enhancement effect for intermediate thickness samples; in this context both monochromatic and bichromatic approaches are adapted to a known theoretical model.
Authors:Ana Reverdito, Mariano García, Alejandra Salerno, Oscar Locani, and Isabel Perillo
When the components of a reaction mixture cannot be quantified by UV-visible spectrophotometry, because the
values of their absorption bands overlap, the components can be separated and quantified by spectrodensitometric thin-layer chromatography (SDTLC). In this work an aminolysis reaction mixture in aqueous medium was studied by TLC on silica gel plates with densitometric detection. The reaction, an intramolecular rearrangement involving migration of an acyl group, was studied by monitoring a carbinolamine intermediate for which
was identical with those of the substrate and product. SDTLC not only enabled detection of all three components of the mixture when the plate was developed but also enabled detection of covalent and ionic forms of the reaction intermediate by comparison of their absorbance/reflectance spectra with those of structurally related imidazolidine and amidinium salt derivatives, respectively, used as model compounds. Kinetic studies, among others, may also be performed by SDTLC to determine the mechanism of the reaction.
An improved method based on the moderation of intermediate neutrons for the measurement of hydrogen in small samples is described.
With the aid of boron and cadmium filters, a space shielded from slow neutrons is set up close to an isotopic neutron source
shrouded by water moderator. A BF3 proportional counter enclosed with a sample cell is placed in this space. The neutron count rate of the counter increases
when a hydrogen-containing material is introduced into the cell, due to the moderation of intermediate neutrons passing through
the filters. With a 1.3 μg252Cf neutron source, the lower limit of hydrogen detection for 200 ml samples in 10 min count time is 0.01 wt.%. This method
is suitable for measuring the H2O content of heavy water.