Mechanism of decomposition of manganese(II) oxalate dihydrate and manganese(II) oxalate trihydrate

Oxalate Biominerals

“…for example [52,53]), and in the case of manganese(II) a trihydrated oxalate, MnC 2 O 4 ·3H 2 O, is also known [54,55], and has been found in some mineral deposits (cf. Section 5.4)…”

“…The vibrational spectra of synthetic moolooite samples were also recently investigated, showing some differences with the natural material [177]. Besides, the thermal behavior of humboldtine [178] and moolooite [179] as well as that of the di-and tri-hydrated Mn(II) oxalates [55] were also investigated.…”

Vibrational spectroscopic investigation of the hydrates of manganese(II) oxalate

“…This possibility is also supported by the relatively high bonding energy determined for one of these water molecules (59 kJ/mol). [23] In the same form, the strong 3137 cm −1 band found in γ -Mn(C 2 O 4 ) · 2H 2 O, also suggests in this case the presence of a relatively strong hydrogen bond (H· · ·O lengths, for these stronger bonds, in the order of 1.7 Å). [24] Regarding the deformational modes of the water molecules, they are evidently overlapped by the very strong oxalate bands found around 1600 cm −1 .…”

“…In the first case the dehydration occurs in one unique step, beginning at 130 • C, whereas for the trihydrate it starts at 80 • C and occurs in three steps, in agreement with the presence of structurally different water molecules. [23] The spectrum of γ -Mn(C 2 O 4 ) · 2H 2 O would also suggest the presence of different kinds of water molecules, although the structural study does not show important differences between them [20] and the results of our preliminary study of its thermal behavior, show that water is released in an unique step, beginning at about 145 • C.…”

In situ Thermal Magnetic Investigation of γ-MnC2O4.2H2O Decomposition

“…The thermal investigation was performed in a synthetic air atmosphere (20 ml/min) with sample mass of 2 mg at a heating rate of 10 • C/min in the range of 25-500 • C using LABSYSTEM EVO instrument (SETARAM, France). The measurements of magnetic susceptibility were carried out in the range of 25-300 • C with a Faraday type magnetic balance in accordance with the method described in [ 4,6 ]. The respective weight loss (WL) was also determined.…”