SrCl₂ · 1/2 H₂O und SrCl₂ · H₂O Röntgenographische, thermoanalytische, Raman‐ und IR‐spektroskopische Untersuchungen

Abstract

SrCI2 · 1/2 H2O. konnte mit Hilfe von Hochtemperatur‐Guinier‐ und Hochtemperatur‐Raman‐Messungen nachgewiesen und durch Entwässerung Höherer Hydrate des Strontiumchlorids bei 165°C unter einem Wasserdampfpartialdruck von 1 bar dargestellt werden. Der Verlauf der Entwässerung des SrCI2 · 6 H2O und SrCI2 · 2H2O wird diskutiert. Die Röntgenpulverdaten sowie die IR‐ und Raman‐Spektren des SrCl2 · 1/2 H2O und des SrCI2 · H2O werden mitgeteilt. SrCI2 · H2O Kristallisiert orthorhombisch im BaCl2 · H2O‐Typ (Raumgruppe Pnma) mit a = 1088,1(1), b = 416,2(1) und c = 886,(1) pm. Die Schwingungen der Kristallwassermolekeln sowie die kraftkonstanten und die Bindungsenthalpien der Wasserstoffbrücken werden diskutiert.

On the Thermal Dimorphy of the Strontium Perrhenate Sr[ReO4]2

“…The first signal corresponds to the dehydration of SrCl 2 ⋅ 6 H 2 O, however, since only the loss of half a water molecule per molar unit is observed the precursor powder of formal “SrCl 2 ⋅ 6 H 2 O” has been drained to form a roughly equimolar mixture of SrCl 2 ⋅ H 2 O and SrCl 2 as could be proven later by PXRD measurements. The second signal can be assigned to “Sr[ReO 4 ] 2 ⋅ H 2 O”, which in fact was a mixture of Sr[ReO 4 ] 2 ⋅ H 2 O and Sr[ReO 4 ] 2 ⋅ 2 H 2 O, as indicated by a loss of more than one, but less than two water molecules per molar unit [13–15] …”

“…An exothermal signal at 625 °C in the DSC curve can not be assigned clearly to a particular process, but may be a recrystallization event or a phase transformation. However, the melting point of SrCl 2 [13–15] and the expected melting point of possibly formed Sr 4 OCl 6 [17] both range at higher temperatures. Alternatively, the lower melting point of the reaction mixture could be caused by the formation of dys‐ or peritectica.…”

“…This means that equimolar mixtures of Sr [ O, as indicated by a loss of more than one, but less than two water molecules per molar unit. [13][14][15] Upon further heating no additional signal is observed until 584 °C, revealing that the complete dehydration process of the reaction mixture has already taken place with the previous events. The endothermic signal at 584 °C without any correlating mass loss in the thermogravimetric curve (TG) indicates a possible melting process or a phase transition.…”