Search results for "SOLVENT"
showing 10 items of 1395 documents
Solubility of solid carnosic acid in supercritical CO2 with ethanol as a co-solvent
2005
Abstract The present study is devoted to the experimental measurement and thermodynamic modeling of solid carnosic acid solubility in supercritical CO 2 + ethanol as a co-solvent. Measurements were carried out at temperatures in the range of 313.15 and 333.15 K, pressures ranging from 280 to 400 bar, and at different content of the modifier ethanol (from 0.7 to 10%). The Group Contribution Associating Equation of State (GCA-EoS) [H.P. Gros, S.B. Bottini, E.A. Brignole, High pressure phase equilibrium modeling of mixtures containing associating compounds and gases, Fluid Phase Equilibria 139 (1997) 75–87] was applied in this work to represent the experimental solubility data obtained. Due t…
Formation of Calcium-Deficient Hydroxyapatite via Hydrolysis of Nano-Sized Pure Α-Tricalcium Phosphate
2015
Nano-sized pure α-tricalcium phosphate (α-TCP) fabricated by a novel synthesis approach shows great potential for a faster transformation into calcium-deficient hydroxyapatite (CDHA) than conventionally prepared α-TCP. In this work, amorphous tricalcium phosphate precursors were precipitated and treated with a solvent (water or ethanol), and dried (freeze-dried and oven-dried) before heating at 775 °C. Nanosized α-TCP powders were investigated for their phase composition and crystallinity, particle shape and size, reactivity and cellular biocompatibility. Reaction with water showed faster CDHA formation for freeze-dried powder, at 6 hours, compared to ethanol treated powders, whereas a high…
A green way to gamma-lactams through a copper catalyzed ARGET-ATRC in ethanol and in the presence of ascorbic acid
2011
Abstract A ‘green’ ARGET-ATRC, for the CuCl[PMDETA] catalysed cyclo -isomerization of N -allyl-α-polychloroamides to γ-lactams is described. The process works efficiently (yields 78–96%), uses a bio-solvent, as ethanol, and exploits the reducing feature of ascorbic acid to limit, at a low level (2–4%), the amount of catalyst. To preserve the efficacy of the catalytic cycle, addition of Na 2 CO 3 is essential, which quenches the HCl released during the CuCl[PMDETA] regeneration step. Profitable features of the process are: mild reaction temperatures (25–37 °C), relatively short reaction times (usually 5 h) and low solvent volumes (2 mmol of substrate/mL of ethanol). The method, upon stoichio…
Conductance of potassium lodide in mixed solvents
1976
The conductance of potassium iodide has been measured in the solvents ethylene carbonate, water, methyl ethyl ketone, and pairwise mixtures of these solvents at 40°C; and ethylene carbonate-water, tetramethylene sulfone-water, dimethyl sulfoxide-water, tetrahydrofuran-water, ethylene carbonate-tetramethylene sulfone-water, ethylene carbonate-tetramethylene sulfone, and tetrahydrofuran-dimethyl sulfoxide at 25°C. For dielectric constants greater than about 60, the pairing constants KA are in the range 0.3–2.0; no correlation between KA and solvent properties could be established. For lower dielectric constants, KA increases exponentially with decreasing dielectric constant. Addition of a pro…
Studying the stability of Solvent Red 19 and 23 as excise duty components under the influence of controlled factors
2020
Abstract In this study, we examine the chemical stability of two disazo dyes, namely Solvent Red 19 and 23 (SR 19 and SR 23), under simulated conditions. Both dyes are considered to be chemically stable under normal exploitation conditions and therefore, are used extensively as excise duty components that enable a rapid visual verification of the tax levels that were imposed on fuel products as well as identifying fuel usage. However, the results from this study confirmed that the colour of the samples that had been fortified with either SR 19 or SR 23 fades under the influence of external conditions such as UV-A irradiation and temperature over time. The UV-A irradiation was the dominant f…
Directed Assembly of Soft Colloids through Rapid Solvent Exchange
2015
We studied the directed assembly of soft nanoparticles through rapid micromixing of polymers in solution with a nonsolvent. Both experiments and computer simulations were performed to elucidate the underlying physics and to investigate the role of various process parameters. In particular, we discovered that no external stabilizing agents or charged end groups are required to keep the colloids separated from each other when water is used as the nonsolvent. Furthermore, the size of the nanoparticles can be reliably tuned through the mixing rate and the ratio between polymer solution and nonsolvent. Our results demonstrate that this mechanism is highly promising for the mass fabrication of un…
Highly selective chemical sensing in a luminescent nanoporous magnet.
2012
Among the wide variety of properties of interest that a given material can exhibit, luminescence is attracting an increasing attention due to its potential application in optical devices for lighting equipment and optical storage, [ 1a − c] optical switching, [ 1d ,e] and sensing. [ 1f − i ] At this respect, many scientists, working in the multidisciplinary fi eld of the materials science, have directed their efforts to the obtention of luminescent materials with potential sensing applications. For instance, sensitive and selective detection of gas and vapor phase analytes can result specially interesting because of the variety of applications that can be found in many different fi elds. A …
Studies of short-lived fission products by means of the multistage solvent extraction system SISAK
1990
The multistage solvent extraction system SISAK is described. The system is used for online studies of nuclides with half-lives down to ∼1 s. Some of the chemical separation procedures are presented, and a survey is given on the results obtained so far. The possiblity to gain access to nuclides with even shorter half-lives is also discussed.
Pēc sešiem mirkļiem 100 gadi : izstādes plakāti
2013
Izstāde, kas veltīta Latvijas Universitātes 94. gadadienai, atspoguļo informāciju par 18 LU Kultūras, Mākslas un Izglītības jaunrades biedrības "Juventus" mākslinieciskās pašdarbības kolektīviem.
Approaches to model the retention and peak profile in linear gradient reversed-phase liquid chromatography.
2012
Abstract The optimisation of the experimental conditions in gradient reversed-phase liquid chromatography requires reliable algorithms for the description of the retention and peak profile. As in isocratic elution, the linear relationship between the logarithm of the retention factor and the solvent contents is only acceptable in relatively small concentration ranges of modifier. However, more complex models may not allow an analytical integration of the general equation for gradient elution. Alternative approaches for modelling the retention in linear gradient elution are here proposed. Those based on the quadratic logarithmic model and a model proposed for normal liquid chromatography yie…