Internally consistent thermodynamic dataset for divalent metal sulfate minerals

我们的主要目标是获得一个内部一致的二价金属硫酸盐水合物矿物的热力学数据集。在试点项目中，我们选择了MgS 〇 4- H2O系统来仔细测试我们的方法。最初，拟议的项目包括两个主要部分。第一个是修改和增强以前开发的软件包，用于推导硫酸盐系统中使用的内部一致的数据集。项目的第二部分包括用量热技术测定几种硫酸镁矿物的形成时间。该项目的两个部分都被证明是成功的-我们测量了MgSO 4·H2O（n = 1、2、6、7）的形成过程，并导出了MgSO 4- H2O系统的内部一致数据集，从而能够计算相图。在项目的最后一年，我们希望缩小一些剩余的差距：1。将合成相星沸石（MgS 〇 4·4 H20）并进行量热研究。此外，我们将尝试合成和表征低-7相镁橄榄石（MgSO 4·H2O）。2.在一项开创性的研究中，将使用Salzburg的PPMS®系统通过低温热容（Cp）测量获得泻盐和六水硫酸盐的熵。3.这些数据将用于进一步完善我们的热力学数据集。4.能够用Pitzer公式计算水溶液中离子活度的公式已经写出来了，但是我们仍然需要包括一个描述水溶液和固体的Cp行为的公式。

Our main goal is to derive an internally consistent thermodynamic data set for divalent metal sulfate hydrate minerals. In a pilot project, we have chosen the system MgS04 - H2O to carefully test our approach. Initially, the proposed project consisted of two principal parts. The first one was the modification and augmentation of a previously developed software package for the derivation of internally consistent data sets for the use in the sulfate system. The second part ofthe project included the determination of enthalpies of formation of several magnesium sulfate minerals by calorimetric techniques. Both parts of the project turned out to be successful - we measured the enthalpies of formation of MgS04·H20 (n = 1, 2, 6, 7) and derived an internally consistent data set of the system MgSO4 - H2O enabling the calculation of phase diagrams. In the last year of the project, we want to close some remaining gaps: 1. The phase starkeyite (MgS04-4H20) will be synthesized and investigated calorimetrically. Additionally, we will attempt to synthesize and characterize the low-7 phase meridianiite (MgS04·H20). 2. In a pioneering study, the entropy of epsomite and hexahydrite will be obtained by low temperature heat capacity (Cp) measurements using a PPMS® system at Salzburg. 3. These data will be used to refine our thermodynamic data set further. 4. Routines capable of calculating ion activities in aqueous solutions with the Pitzer fomialism were already written, but we still have to include a formalism describing the Cp behaviour of the aqueous solution and the solids.