E (R3) differs from calcite (R3c) only inside the absence with the c-glide plane due to the alternation of cation layers along the c-axis. Intuitively, the resemblance and similarity involving the element Ca and Mg (alkaline earth metals in adjacent periods) may indicate that the formation of dolomite may be just executed by Mg partially replacing Ca in calcite. The experimental tests as a result far having said that have shown that this conjecture is nowhere close to reality. The difficulty to incorporate Mg into the calcite structure at ambient conditions is overwhelmingly attributed Inositol nicotinate Protocol towards the stronger (relative to Ca2 ) hydration of Mg2 ions [170]. The rationale for this reasoning is definitely the heightened charge density from the Mg2 ion originating in the cation’s smaller size (ionic radius 0.72 relative to Ca2 [21]. Assuming a spherical geometry, the charges per surface location on magnesium cations are hence nearly twice of that on calcium cations. A high surface charge density can result in a substantial charge transfer from ions to solvent, resulting in decreased reactivity on the ions. For magnesium, the net charge on the central Mg2 of Mg[H2 O]6 2 was calculated to be only 1.18 [15]. Also, the hydration energy for Mg2 is estimated at about 30 greater than that for Ca2 [228], indicating indeed a reduce reactivity of Mg2 in an aqueous atmosphere. Oddly, the cation hydration retardation theory doesn’t look to offer valid predictions when applied to siderite (FeCO3 , R3c). Applying precisely the same arguments for the lack of magnesite MgCO3 formation at atmospheric circumstances, the model is set to predict that the ferrous carbonate phase is a minimum of equally tough to crystallize in ambient aqueous solutions offered that Fe2 includes a related size (0.61 0.78 depending around the spin state) along with a slightly higher ( 7 ) hydration power in comparison with Mg2 . Having said that, it is actually well-known [29] that siderite mineralizes often at surface conditions, including in the scale layers on steel pipes in industrial settings related to oil and gas production and transportation. Additional critically, direct tests of magnesite crystallization in the absence of water (i.e., non-aqueous Mg2 solvation) haven’t supported the Mg hydration theory. Crucially insightful data with regard for the non-aqueous synthesis of MgCO3 was 1st provided by a century-old study exactly where Neuberg and Rewald [30] examined the interactions of CO2 gas with CaO and MgO in methanolic suspensions. In the case of CaO, a gel-like compound was obtained and subsequently identified as calcite. For the MgO experiment, no strong solution was observed in the end. A a lot more current study [31] at settings slightly different (larger T and P at 500 C and three bar pCO2 ) from those employed by Neuberg and Rewald obtained an anhydrous magnesium carbonate precipitate but only located to become nano-aggregates of amorphous MgCO3 . In light on the hydration retardation theory’s implication that magnesite (and dolomite) should really crystallize if the hydration shell around Mg2 is breached or weakened, these results appear to strongly contradict the assumed hydration impact as all the PF-06454589 Technical Information syntheses have been performed inside the absence of water. An even more intriguing case inconsistent using the Mg hydration retardation theory would be the binary carbonate mineral norsethite MgBa(CO3 )2 [32,33]. Apart from the size difference amongst the cation pairs of Mg vs. Ba ( 0.eight and Mg vs. Ca ( 0.three , norsethite is quite similar to dolomite structure-wise, using the primary distinction being that th.