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1.
Zusammenfassung In der vorliegenden Arbeit wird das Sedimentationsgleichgewicht der Systeme Na6[H2W12O40]—NaCI—H2O und Na6[H2W12O40]—NaClO4— H2O untersucht. Die scheinbare molare Masse Mapp des Natriummetawolframats wird in beiden Systemen als Funktion der Natriummetawolfrarnat-Anfangspartialdichte
0
PX
z gemessen. Durch lineare Extrapolation der Funktion Mapp = Mapp (PP,, ) auf die Polymerelektrolyt-Anfangspartialdichte Null können die Grenzwerte der scheinbaren molaren Masse (Mapp)o ermittelt werden. Aus den (Mapp)o-Werten wird die Abhängigkeit der Größe (ln
PXz
/m
BX
)
mPXz von der NaCI- bzw. NaClO4-Molalität berechnet.Die Bestimmung der molaren Masse und der (stöchiometrischen) Ladungszahl eines Polymerelektrolyten aus den experimentell ermittelten (Mapp)o-Werten unter Anwendung der Lamm-Williams-Gleichung wird diskutiert. Zur Ermittlung der beiden Größen müssen mehrere Versuchsreihen mit zwei verschiedenen Fremdelektrolyten durchgeführt werden. Externe Messungen sind nicht erforderlich.Man erhält auf diese Weise verläßliche Werte so-wohl der molaren Masse als auch der (stächiometrischen) Ladungszahl.
Mit 5 Abbildungen und 3 Tabellen 相似文献
Summary The sedimentation equilibria of the systems sodium metatungstate-sodium chloride-water and sodium metatungstate-sodium perchlorate-water are investiated. In both systems the apparent molecular mass Mapp of sodium metatungstate (PX z) is measured in dependence on partial density 0 PX z before centrifugation. By linear extrapolation of the function Mapp = Mapp ( 0 PX z the limiting value (Mapp)o for 0 PX z = 0 is obtained. The variation with sodium chloride and sodium perchlorate molality of the quantity (ln PX z m BX )mPXz is calculated from (Mapp)o data.The determination of the molecular mass and the algebraic valency of a polymeric ion by means of the (Mapp)o values calculated by Lamm-Williams equation is discussed. In order to obtain these two quantities at least two series of experiments are required, each of which using a different supporting electrolyte. External measurements are not necessary. In this way reliable values for the molecular mass as well as for the stoichiometric valency are obtained.
Mit 5 Abbildungen und 3 Tabellen 相似文献
2.
Zusammenfassung In der vorliegenden Arbeit wird das Sedimentations-gleichgewicht des Systems Na6[H2W12O40]-NaClO4-H2O bei 25 °C untersucht. Die scheinbare Ladungszahl des Natriummetawolframats wird als Funktion der NaClO4-MolalitätmNaClO4 ermittelt. Aus dieser Abhängigkeit kann für die summarische Dissoziation des NatriummetawolframatsNa2[H2W12O4o] 6Na+ + [H2W12O40]6– die DissoziationskonstanteK in Gegenwart von NaClO4 als Fremdelektrolyt zuK=0,08 mol6·kg–6 bestimmt werden.Der Kreuzdifferentialquotient
(
PXz
, ist der Trace-Aktivitätskoeffizient des Natriummetawolframats) wird ebenfalls als Funktion der NaClO4-Molalität ermittelt.Die Konzentrationsabhängigkeit des Trace-Aktivitätskoeffizienten zeigt einen Verlauf, wie er unseres Wissens nach noch nicht von anderen Autoren beobachtet wurde.
Mit 5 Abbildungen und 1 Tabelle 相似文献
Summary An ultracentrifugal study of the sedimentation equilibrium of the system Na2[H2W12O40]-NaClO4-H2Oat 25 °C is presented. The dependency of the apparent charge of the sodium metatungstate on NaClO4-molality is investigated. From these data the dissociation constant for the dissociation of the sodium metatungstate in the presence of NaClO4 according to the equationNa[H2W12O40] 6Na+ + [H2W12O40]6– is calculated toK=0.08 mol6·kg–6. The cross differential quotient ( PXz is the trace activity coefficient of the sodium metatungstate) shows a behavior in its dependence on NaClO4-molality which to our knowledge has not yet been reported by other authors.
Mit 5 Abbildungen und 1 Tabelle 相似文献
3.
John T. Stock 《Trends in analytical chemistry : TRAC》1983,2(11):261-262
The automatic control of certain physical phenomena, such as temperature and speed of rotation, has long been commonplace. However, the means by which this form of control can be applied to a chemical process are not so obvious. A sensing system must be found to monitor the status of the particular chemical system. 相似文献
4.
5.
6.
We have observed phase defects in quasi-2D Bose-Einstein condensates close to the condensation temperature. Either a single or several equally spaced condensates are produced by selectively evaporating the sites of a 1D optical lattice. When several clouds are released from the lattice and allowed to overlap, dislocation lines in the interference patterns reveal nontrivial phase defects. 相似文献
7.
Windsor WL Desain P Penel A Borkent M 《The Journal of the Acoustical Society of America》2006,119(2):1182-1193
A method for separating, profiling, and quantifying the contributions of different structural components to expressive musical performance is described. The method is demonstrated through its application to a set of expert piano performances of a short piece from the classical period. The results show that the output of the method aids in the understanding of how the different structural components in a piece of music combine in the generation of an expressive performance. A second demonstration applies the method to performances at different tempi to illustrate its effectiveness in pinpointing the structural features responsible for small but statistically significant differences between performances. The method is compared with other approaches to the analysis and modeling of musical performance, and a number of potential applications are identified. 相似文献
8.
Choi SK Coldea R Kolmogorov AN Lancaster T Mazin II Blundell SJ Radaelli PG Singh Y Gegenwart P Choi KR Cheong SW Baker PJ Stock C Taylor J 《Physical review letters》2012,108(12):127204
We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order. The onset of long-range magnetic order below T(N)=15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90° Ir-O-Ir bonds required for dominant Kitaev exchange. 相似文献
9.
Stone M Stock G Bunin K Kumar K Epstein M Kambhamettu C Li M Parthasarathy V Prince J 《The Journal of the Acoustical Society of America》2007,122(1):532-541
Speech is usually produced in an upright sitting or standing posture. Measurements and judgments of speech may be made in conditions requiring a supine position, however. These conditions include MRI recordings, and oral procedures, such as, adjustments to dental appliances, medical and surgical procedures. It is of interest, therefore, to see whether gravity has strong or systematic effects on tongue behavior. In the present study, 13 subjects repeated several words, which contained extreme consonant and vowel tongue positions, during upright and supine condition. Ultrasound imaging provided midsagittal tongue contours, in each condition, for comparison. A neck brace was used to stabilize transducer placement and the palate was used as a physiological reference to register the data sets. Results showed a significant subject effect. In supine position the tongue was more posterior than upright for seven subjects, more anterior for two subjects and varied by phoneme for four subjects. However, there was no significant phoneme effect. The direction of change and the amount of change were not directly related. Most subjects had small upright-supine differences. The largest differences, less than 3 mm on average, were in the posterior tongue. 相似文献
10.