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Updated: Dec 22, 2025

Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence
Published on: September 23, 2018
Sodium sulfite heptahydrate and its relation to sodium carbonate heptahydrate
Matthias Weil1, Kurt Mereiter1
1Institute for Chemical Technologies and Analytics, Division of Structural Chemistry, TU Wien, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria.
Abstract:
The monoclinic crystal structure of Na2SO3(H2O)7 is characterized by an alternating stacking of (100) cationic sodium-water layers and anionic sulfite layers along [100]. The cationic layers are made up from two types of [Na(H2O)6] octahedra that form linear 1∞[Na(H2O)4/2(H2O)2/1] chains linked by dimeric [Na(H2O)2/2(H2O)4/1]2 units on both sides of the chains. The isolated trigonal-pyramidal sulfite anions are connected to the cationic layers through an intricate network of O-H...O hydrogen bonds, together with a remarkable O-H...S hydrogen bond, with an O...S donor-acceptor distance of 3.2582 (6) Å, which is about 0.05 Å shorter than the average for O-H...S hydrogen bonds in thiosalt hydrates and organic sulfur compounds of the type Y-S-Z (Y/Z = C, N, O or S). Structural relationships between monoclinic Na2SO3(H2O)7 and orthorhombic Na2CO3(H2O)7 are discussed in detail.
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