Search results for "Diss"
showing 10 items of 2500 documents
Thermometric study of the dissociation equilibria of the maleinimidodioxime
1982
The values of the dissociation constants of the maleinimidodioxime are potentiometrically determined at various ionic strengths, and extrapolated to zero ionic strength (pK1T=10.41;pk2T=11.60). From these values and from the thermometric titration curves the enthalpies of neutralization (ΔHN1=−21.76,ΔHN2=−23.77 kJ/mol) and the thermodynamic parameters of dissociation of this substance at 25.0 °C are determined (ΔG1θ=59.41,ΔG2θ=66.23,ΔH1θ=34.06,ΔH2θ=32.05 kJ/mol;ΔS1θ=−85.06,ΔS2θ=−114.64 J/(K mol)).
Leitfahigkeitsmessungen an Polystyrylnatrium in Dimethoxiäthan (DME) und Tetrahydrofuran (THF)
1971
An Polystyrylnatrium werden in zwei polaren organischen Losungsmitteln Leitfahigkeitsmessungen uber einen groseren Temperaturbereich ausgefuhrt. Aus der Temperaturabhangigkeit der Dissoziationskonstante ergibt sich, das die undissoziierte Verbindung in zwei Formen, dem Kontaktionenpaar (I) und dem solvatgetrennten Ionenpaar (II), vorkommt. Enthalpie- und Entropiedifferenz beim ubergang von I nach II, sowie die entsprechenden thermodynamischen Parameter der Dissoziation von II werden ermittelt. Der effektive Ladungsabstand im solvatgetrennten Ionenpaar betragt etwa 7 A. Conductivity measurements were carried out with polystyryl sodium in two polar solvents within a large temperature range. T…
The Dissociation Constant of Pyruvic Acid: Determination by Spectrophotometric Measurements
1991
Aqueous solutions of sodium pyruvate/hydrochloric acid mixtures were studied with regard to changes in the intensity of optical absorption at 317 nm wavelength, caused by varying pH and temperature. The data were evaluated to determine the pyruvic acid apparent dissociation constant at infinite dilution. Its temperature dependence followed the relation ln Kod = −(0.55 ± 0.47) − (1538 ± 135)/T or, if previous results of Pedersen at two temperatures are included, In Kod = −(0.97 ± 0.35) − (1418 ± 102)T. The effective absorption coefficient for pyruvic acid and its anion differ because the former species is largely hydrated, whereas the latter is not. The known hydration constant and its tempe…
1984
Zur kinetik der anionischen polymerisation von methyl-methyacrylat in tetrahydrofuran bei −75°C
1973
Die anionische Polymerisation von Methylmethacrylat (MMA) in Tetrahydrofuran (THF) verlauft bei −75°C mit Cumylcasium bzw. oligomerem α-Methylstyrylcasium als Initiatoren ohne erkennbare Nebenreaktionen analog der anionischen Polymerisation von unpolaren Monomeren in atherischen Losungsmitteln. Als Beweis wird hauptsachlich die enge Molekulargewichtsverteilung der unter diesen Bedingungen hergestellten Polymethylmethacrylate angefuhrt. Bei −75°C betragen die Geschwindigkeitskonstanten fur die Monomeranlagerung an das Ionenpaar kw(±) = 80 dm3 mol−1 s−1 und an das freie Anion etwa kw(−) ≈ 6 · 104 dm3 mol−1 s−1. Leitfahigkeitsmessungen ergeben, das die Dissoziationskonstante des Polymethylmeth…
Calcification is not the Achilles'heel of cold-water corals in an acidifying ocean
2015
Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Omega ara) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2 1058 µatm, Omega ara 1.29),…
On the interlayer spacing collaps of the Cloisite® 30B organoclay
2011
Spatial and seasonal changes of dissolved and particulate organic C in the North Sea
2009
Sampling of the central region of the North Sea was carried out to study the spatial and seasonal changes of dissolved and particulate organic C (DOC and POC, respectively). The surface waters were collected during four cruises over a year (Autumn 2004–Summer 2005). DOC and POC concentrations were measured using high temperature catalytic oxidation methods. The surface water concentrations of DOC and POC were spatially and temporally variable. There were significantly different concentrations of DOC and POC between the inshore and offshore waters in winter and summer only, with no clear trend in autumn and spring. Highest mean concentrations of DOC were measured in spring with lower and sim…
Widening the applicability of AnMBR for urban wastewater treatment through PDMS membranes for dissolved methane capture: Effect of temperature and hy…
2021
[EN] AnMBR technology is a promising alternative to achieve future energy-efficiency and environmental-friendly urban wastewater (UWW) treatment. However, the large amount of dissolved methane lost in the effluent represents a potential high environmental impact that hinder the feasibility of this technology for full-scale applications. The use of degassing membranes (DM) to capture the dissolved methane from AnMBR effluents can be considered as an interesting alternative to solve this problem although further research is required to assess the suitability of this emerging technology. The aim of this study was to assess the effect of operating temperature and hydrodynamics on the capture of…
Natural Organic Compounds in Soil Solution: Potential Role as Soil Quality Indicators
2013
This review focuses on the chemical nature of that fraction of already dissolved organic matter into soil solution, or extracted by mild extractants, which is truly readily available for microbial activity and, consequently, more sensitive than total soil organic matter to changes in management and/or environmental conditions. In particular, we deal with low molecular weight compounds such as monosaccharides, amino sugars and amino acids. Soil sampling strategy and extraction procedure, prior to analyses, are crucial to make comparable results among laboratories. Although soil management and climatic conditions may cause large variability, extractable organic C and N may indicate the amount…