Chemische Untersuchungen von Silicaten, XXXI. Über Beziehungen zwischen dem Polymerisationsgrad silicatischer Anionen und ihrem Reaktionsvermögen mit Molybdänsäure

Abstract

Es werden die Geschwindigkeiten bestimmt, mit denen sich aus Silicaten verschiedene Konstitution Silicomolybdänsäure bildet. Aus Mono‐, Di‐ und Tetrametasilicaten bildet sich der Komplex nach einem Gesetz erster Ordnung mit den Geschwindigkeitskonstanten kMono = 1,7 min−1, kDi = 0,90 min−1 und kTetrameta = 0,67 min−1. Höherkondensierte Silicate werden beim Lösen zum Teil abgebaut. Ihre höchstmolekularen Anteile reagieren aber eben falls nach einem Gesetz erster Ordnung, wobei die Geschwindigkeitskonstanten gesetzmäßig vom (Na2O:SiO2)‐Verhältnis bzw. vom Kondensationsgrad abhängen. Ihrer Reaktionsgeschwindigkeit nach enthalten die Ca2SiO4‐γ‐Hydrate (C I‐ und C II‐Hydrat) mono‐ und dimere, das Ca2SiO4‐β‐Hydrat (B‐Hydrat) und ein Mg‐Silicathydrat hochmolekulare Kettenanionen.

The formation of glass: a quantitative perspective

“…By contrast, the crystallization constants of KNO 3 , RbNO 3 and CsNO 3 are relatively small, corresponding to ease of glass formation. These findings are consistent with the experimental results reported by Thilo et al [148]; furthermore, they allow for quantitative interpretations of GFA. Unlike Thilo et al [148], who determined the ease of glass formation based on the difference in field strength, we applied thermodynamics and kinetics to make quantitative predictions of the locations of the glass-forming region using mathematical methods.…”

“…These findings are consistent with the experimental results reported by Thilo et al [148]; furthermore, they allow for quantitative interpretations of GFA. Unlike Thilo et al [148], who determined the ease of glass formation based on the difference in field strength, we applied thermodynamics and kinetics to make quantitative predictions of the locations of the glass-forming region using mathematical methods. There are some deviations between the calculations and the actual glass-forming regions in the case of binary systems that contain RbNO 3 , which may be attributed to the use of an inaccurate value for the heat of fusion for RbNO 3 .…”

“…In a binary nitrate melt, glass formation only occurs in a system that contains both monovalent and divalent nitrates; it is difficult for a system that contains either only monovalent or only divalent nitrates to form glass. Thilo et al [148] studied multiple binary nitrate glass systems, and their research concerning the field strengths of positive ions indicated that glass forms when the difference in the field strengths of positive ions is greater than 0.7. However, this difference in the field strengths of positive ions does not cause negative ions to be distorted during glass formation.…”

“…However, this difference in the field strengths of positive ions does not cause negative ions to be distorted during glass formation. Although the field-strength-based analysis contributes to the classification of the nitrate system based on its difficulty or facility of glass formation, determining the glass-forming regions of specific systems based on this analysis remains difficult [49,147,148]. Thilo et al [148] experimentally observed nitrate glass-forming regions near the eutectic regions, and they found that the glass-forming regions became larger as the eutectic region became lower.…”

“…Although the field-strength-based analysis contributes to the classification of the nitrate system based on its difficulty or facility of glass formation, determining the glass-forming regions of specific systems based on this analysis remains difficult [49,147,148]. Thilo et al [148] experimentally observed nitrate glass-forming regions near the eutectic regions, and they found that the glass-forming regions became larger as the eutectic region became lower. From the dynamical perspective, a lower temperature implies a higher viscosity, and it is easier to form glass when the degree of under cooling of the eutectic glass-forming region is lesser.…”