Authors:Sonia Freire, H. Casas, Esther Rilo, Luisa Segade, O. Cabeza, and E. Jiménez
Summary In this paper we present excess molar volumes and excess molar enthalpies of binary and ternary mixtures containing propyl propanoate, hexane and cyclohexane as components at 298.15 K. Excess molar volumes were calculated from the density of the pure liquids and mixtures. The density was measured using an Anton Paar DMA 60/602 vibrating-tube densimeter. Excess molar enthalpies were obtained using a Calvet microcalorimeter
The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical
processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical
properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB
rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure
the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining life-time of DB rocket
In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures,
in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties
were studied using dynamic mechanical analyser (DMA).
The results obtained have shown that the ageing causes significant changes of DMA curve’s shape and positions. These changes
are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus,
loss modulus and tanδ at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the
ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass
transition and softening temperature, and tanδ at viscoelastic region.
Instrumental neutron activation analysis (INAA) was used to determine trace elemental contamination in bird feathers. Primary
feathers from twelve mallard (Anas platyrhynchos) ducks, migrating through the Thousand Islands region of Ontario, Canada, were analyzed for selenium, mercury, chromium,
arsenic and antimony. Certified reference materials were used to assess the quality of the analytical procedure. Quantification
of chemical elements was performed using Ortec Gamma Vision software. Five chemical elements were quantified, with corresponding
analytical uncertainties of less than 20%. Results indicated the presence of As (max = 0.13 mg kg−1), Cr (max = 2.6 mg kg−1), Hg (max = 7.7 mg kg−1), Sb (max = 0.31 mg kg−1) and Se (max = 1.31 mg kg−1). To assess the validity of using INAA as a quantitative analytical technique for feather samples, two standard reference
materials were examined and mercury results were compared to those obtained from both direct mercury analysis (DMA) and cold
vapour atomic absorption spectroscopy (CVAAS). Several CVAAS results differed significantly from the INAA results; in many
instances CVAAS appeared to under-report when compared to INAA, with relative percent difference values as high as 126%. Conversely,
results obtained using DMA compared favourably with INAA. For all samples, RPD values were within 30%. This is the first study
to use INAA to examine feather contamination in Canadian migratory waterfowl and the first to corroborate INAA feather results
by comparing them to those obtained using CVAAS and DMA.
Authors:P. Verdes, M. Mato, J. Legido, and M. Paz Andrade
Densities at 298.15 K and atmospheric pressure have been measured, using a DMA 4500 Anton Paar densimeter, for the ternary
mixture methyl tert-butyl ether (MTBE)+1-pentanol+nonane and for the involved binary mixture 1-pentanol+nonane. In addition, excess molar volumes
were determined from the densities of the pure liquids and mixtures. Suitable fitting equations have been used in order to
correlate adequately the excess molar volumes.
Experimental data were also used to test several empirical expressions for estimating ternary properties from experimental
Authors:Malgorzata Wszelaka-Rylik and W. Zielenkiewicz
Calorimetric and volumetric investigations of ovalbumin salting by sodium
chloride, lithium chloride, potassium chloride, lithium sulfate and ammonium
sulfate buffered solutions in the range of concentrations of about 0.2–1.2
M of salts are reported. The evolution of enthalpies and apparent molar volumes vs. salts concentration was investigated using ITC
MicroCal titration microcalorimeter and Anton Paar DMA 60/602 digital densimeter.
It was found that the changes in enthalpies of salting and apparent molar
volumes follow a similar trend. Conclusions about the ability of salts: to
precipitate ovalbumin solution are presented.
Authors:M. M. Mato, S. M. Cebreiro, P. V. Verdes, J. L. Legido, and M. I. Paz Andrade
Summary Experimental excess molar enthalpies and excess molar volumes of the ternary system x1MTBE+x21-propanol+(1-x1-x2) hexane and the involved binary mixtures have been determined at 298.15 K and atmospheric pressure. Excess molar enthalpies were measured using a standard Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a DMA 4500 Anton Paar densimeter. The UNIFAC group contribution model (in the versions of Larsen et al., and Gmehling et al.) has been employed to estimate excess enthalpies values. Several empirical expressions for estimating ternary properties from experimental binary results were applied.
Authors:M. M. Mato, S. M. Cebreiro, P. V. Verdes, A. V. Pallas, J. L. Legido, and M. I. Paz Andrade
Summary Experimental densities for the ternary mixture x1MTBE+x21-propanol+(1-x1-x2)decane and the binary mixtures xMTBE +(1-x)1-propanol and x1-propanol+(1-x)decane have been measured at 298.15 K and atmospheric pressure, using a DMA 4500 Anton Paar densimeter. Excess molar volumes were determined from the densities of the pure liquids and mixtures. Attending to the symmetry of the studied mixtures, suitable fitting equations have been used in order to correlate adequately the experimental data. For the ternary mixture, experimental data were also used to test several empirical expressions for estimating ternary properties from experimental binary results.
Authors:W. James, T. Raghvan, T. Gentry, G. Shan, and R. Loeppert
Sensitivities for the measurement of four arsenic species, AsIII, AsV, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in environmental waters and rice extracts by a new neutron
activation analysis (NAA) method using pre-separation of the species by liquid chromatography were determined. A manual fraction
collection was used to isolate the species, followed by instrumental neutron activation analysis procedures. The sensitivities
determined for arsenic species in the samples varied from 1.21 to 1.47 ng per vial or about 30 μg·L−1 in sample solutions which translates to about 900 ng arsenic per gram of rice for our HPLC-NAA experiments.
Thermal and dynamic mechanical properties of carbon dioxide and propylene oxide alternative copolymer, poly(propylene carbonate) (PPC), and the end-capped PPC with maleic anhydride were investigated by means of TG and DMA. A master curve of the storage modulus vs. frequency can be deduced from the isochronal curves. Physical parameters of both plain and MA end-capped PPC were discussed. The results showed that for maleic anhydride (MA) end-capping PPC, an improvement of its thermal stability and mechanical properties accompanied with some modifications of the viscoelastic behavior were obtained.
Authors:J. Van Elteren, H. Das, C. De Ligny, J. Agterdenbos, and D. Bax
Differentiation between As(III) and As(V) is accomplished using earlier developed selective preconcentration methods (carbamate and molybdate mediated (co)precipitation of As(III) and As(V) respectively) follewed by AAS detection of the (co)precipitates. Apart from this, separation of methylated arsenic species is performed by an automatable system comprising a continuous flow hydride generation unit in which monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) are converted into their corresponding volatile methylarsines, monomethylarsine (MMA) and dimethylarsine (DMA) respectively. These species are cryogenically trapped in a Teflon-line stainless stell U-tube packed with a gas chromatographic solid-phase and subsequently separated by selective volatilization. A novel gas drying technique by means of a Perma Pure dryer was applied successfully prior to trapping. Detection is by atomic absorption spectrometry (AAS). MMAA and DMAA are determined with absolute limits of detection of 0.2 and 0.5 ng, respectively. Investigation of the behaviour of the methylarsines in the system was conducted with synthesized73As labeled methylated arsenic species. It was found that MMA is taken through the system quantitatively whereas DMA is recovered for about 85%. The opumized system combined with selective As(III)/As(V) preconcentration has been tested out for arsenic speciation of sediment interstitial water from the Chemiehaven at Rotterdam. The obtained concentrations are 28.5, 26.8 and 0.60 ng·ml–1 for As(III), As(V) and MMAA, respectively, whereas the DMAA concentration was below 0.16 ng·ml–1.