Bestimmung von Ionenaktivitätskoeffizienten in wässrigen Lösungen mit Hilfe ionenselektiver Elektroden

Abstract

Für die Modellierung der Versuche mit reaktiven Mischungen wurde aufgrund dieser Ergebnisse die Modellvariante offene Verdampfung gewählt.Abb. 8 zeigt ein typisches Ergebnis einer Modellvorhersage, die mit dem oben beschriebenen Stufenmodell für die partielle reaktive Verdampfung einer Formaldehyd/ Wasser-Mischung erzielt wurde. Die Übereinstimmung zwischen den Messwerten und den Modellvorhersagen ist nicht nur für die pauschalen Zusammensetzungen des Kopf-und Sumpfprodukts gut, sondern auch für die besonders wichtige Speziesverteilung im Sumpfprodukt.

On the measurement of individual ion activities

“…In addition, Lin and Lee [12], Lee et al [13], and Schneider et al [14,15] have performed similar measurements and confirmed our results. The theory supporting the method used for these measurements was further elaborated in the work by Rodil and Vera [10] and all values of individual ions activity coefficients measured by our group were recently revised to correct for an error in sign of the term used to estimate the junction potential [11].…”

“…In any case, these numbers are not constant in the range of integration required by Eq. (14). Only assuming, as Malatesta does [25], that S − is exactly identical to (−RT/F) and t + is constant, we would obtain:…”

“…This fact suggests that the effect of errors in the estimate of the junction potential is also absorbed, in a way to be discussed below, by the process of calibration of the electrodes. Schneider et al [14,15] have used a slight modification of our method and considered the slope S i to be identical to its Nernstian value (RT/z i F). This assumption may not be justified.…”

On the measurement of the real values of individual ionic activities: A chemical engineering perspective

“…The basic question is: 'Are the ionic activity coefficients measurable as claimed by us (Khoshkbarchi and Vera, 1996;Wilczek-Vera et al, 2004, 2010Wilczek-Vera and Vera, 2009a) and also by other researchers (Shatkay and Lerman, 1969;Lee et al, 2002;Schneider et al, 2003Schneider et al, , 2004Zhuo et al, 2008) or, as claimed by Malatesta (2009Malatesta ( , 2010 the real values are still unknown?' The term 'real' is used here in the sense of the actual value of the physical property, the value that can be used for chemical engineering design.…”

Activities of aqueous Na+ and Cl- ions from homoionic measurements with n

“…We will not repeat the arguments here, but the interested reader can find in recent literature (Malatesta, 2006a;Wilczek-Vera et al, 2006a) all details and pertinent references of previous discussions on the subject. Although independent measurements in other laboratories (Lee et al, 2002;Schneider et al, 2003Schneider et al, , 2004 have confirmed the repeatability of results obtained by the method proposed by Khoshkbarchi and Vera (1996) to measure individual ionic activities, it may be argued that the same biased assumptions were used in all cases. This work presents innovative experiments designed to provide independent tests of the method to measure the activity of individual ions.…”