NaCl MgCl2 H2O Research Articles

Solid–Liquid Phase Equilibria of NaCl–NH4Cl–MgCl2–H2O and Its Subsystems NaCl–NH4Cl–H2O and NaCl–MgCl2–H2O at T = 303.15 K

Solid–Liquid Phase Equilibria of NaCl–NH₄Cl–MgCl₂–H₂O and Its Subsystems NaCl–NH₄Cl–H₂O and NaCl–MgCl₂–H₂O at <i>T</i> = 303.15 K

Volumetric Properties of Aqueous NaCl−MgCl2−H2O and KCl−MgCl2−H2O Solutions and Their Correlation with the Pitzer Model

The densities of aqueous solutions NaCl–MgCl2–H2O and KCl–MgCl2–H2O have been measured by vibrating-tube densimetry at 5 K intervals over the temperature range of 288 ≤ T/K ≤ 323 at atmospheric pressure. An experimental study was carried out for four total ionic strengths, for which the ionic strength fraction of MgCl2 was 0.2, 0.4, 0.6 and 0.8. The ion interaction approach developed by Pitzer was used to correlate the volumetric properties of aqueous mixtures. The mixing parameters of the Pitzer model were obtained by the least squares method. The calculated results are in good agreement with the experimental and literature data. The volume of mixing at constant ionic strength and at 298.15 K was calculated.

Cryogenic Raman Spectroscopic Studies on Common Ore-forming Fluid Systems

The composition and properties of ore-forming fluids are key to understanding the mechanisms of mineralization in ore deposits. These characteristics can be understood by studying fluid inclusions. Hydrates in fluid inclusions containing NaCl–H2O and MgCl2–H2O were studied using cryogenic Raman spectroscopy. The intensity ratio of peaks at 3401, 3464, 3514, and 3090 cm−1 shows a positive correlation with the concentration of hydrates in the inclusions, as does the ratio of the total integrated area of the MgCl2 hydrate peak (3514 cm−1) to the 3090 cm−1 peak with the concentration of MgCl2 (correlation coefficient &gt;0.90). These correlations are important in the quantitative analysis of MgCl2 in synthetic and natural NaCl–MgCl2–CaCl2–H2O-bearing fluid inclusions. Semi-quantitative analysis of NaCl–MgCl2–H2O solutions indicates that peaks at 3437 and 3537 cm−1 reflect the presence of NaCl in the solution. Further, a peak at 3514 cm−1 is indicative of the presence of MgCl2. The relative intensities of these peaks may be related to the relative abundances of NaCl and MgCl2. A quantitative attempt was made on NaCl–MgCl2–CaCl2–H2O system, but it was found that quantifying NaCl, MgCl2 and CaCl2 separately in NaCl–MgCl2–CaCl2–H2O system by the secondary freezing method is difficult.

Stable Phase Equilibria in Quaternary LiCl–NaCl–MgCl&lt;sub&gt;2&lt;/sub&gt;–H&lt;sub&gt;2&lt;/sub&gt;O and NaCl–Na&lt;sub&gt;2&lt;/sub&gt;B&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;–MgCl&lt;sub&gt;2&lt;/sub&gt;–MgB&lt;sub&gt;4&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;–H&lt;sub&gt;2&lt;/sub&gt;O Systems at 273 K

Phase equilibria of quaternary LiCl–NaCl–MgCl2–H2O and NaCl–Na2B4O7–MgCl2–MgB4O7–H2O systems at 273 K were studied by isothermal dissolution. The isothermal solubility of each salt was measured. Based on the experimental data and the corresponding equilibrium solid phases, equilibrium phase diagrams and water content diagrams were drawn. The results show that the quaternary LiCl–NaCl–MgCl2–H2O system forms a double salt LiCl·MgCl2·7H2O at 273 K. The phase diagram contains two invariant points, five univariant curves and four crystalline regions. The crystalline regions are LiCl·2H2O, NaCl, MgCl2·6H2O and LiCl·MgCl2·7H2O, respectively. There are two invariant points, five univariant curves and four crystallizing fields in the quaternary NaCl–Na2B4O7–MgCl2–MgB4O7–H2O system at 273 K, and the corresponding crystallizing fields are NaCl, Na2B4O7·10H2O, MgCl2·6H2O and MgB4O7·9H2O.

Mineral solubilities of salts in the three quaternary systems: LiCl–NaCl–MgCl2–H2O, LiCl–KCl–MgCl2–H2O and Li2SO4–K2SO4–MgSO4–H2O at 288.15 K

In this paper, the stable phase equilibria of the quaternary systems LiCl–NaCl–MgCl2–H2O, LiCl–KCl–MgCl2–H2O and Li2SO4–K2SO4–MgSO4–H2O were studied at 288.15 K using an isothermal dissolution equilibrium method and the solubility of each system was measured. Based on experimental solubility data, the dry salt diagrams and the diagrams of water-content vs composition of three quaternary systems were plotted. In addition to the single salts, there is a double salt LiCl·MgCl2·7H2O formation at 288.15 K in quaternary system LiCl–NaCl–MgCl2–H2O. In quaternary system LiCl–KCl–MgCl2–H2O, there are two kinds of double salt LiCl·MgCl2·7H2O and KCl·MgCl2·6H2O. It has been found that LiCl has a strong salting-out effect on both NaCl and KCl, which result in NaCl and KCl having larger crystallization regions in each phase diagram. At 288.15 K, the phase diagram of quaternary system Li2SO4–K2SO4–MgSO4–H2O has phase fields of single salt Li2SO4·H2O, K2SO4 and MgSO4·7H2O, and that of double salts K2SO4·MgSO4·6H2O and Li2SO4·K2SO4. The solubilities of the three quaternary systems at 288.15 K were calculated by using the Pitzer electrolyte solution theory model. The parameters involved but not previously reported were obtained by using the solubility data of ternary subsystems and the method of multivariate linear regression. The results show that the calculated results are in good agreement with the experimental results.

Phase diagram of the NaCl–MgCl2–H2O system at 25–75°C and its application for MgCl2 · 6H2O purification

The co-saturation line for the solid phases NaCl(s) and MgCl2 · 6H2O(s) in aqueous solution has been measured by a phase equilibrium at various temperatures. It was found that the Y b (Y b = w(NaCl)/(w(NaCl) + w(MgCl2))) value of the co-saturation line increase with increasing temperature. A new recrystallization approach has been suggested for the purification of MgCl2 · 6H2O(s) containing quite amount of impurity NaCl, i.e., dissolving the crude sample at low temperatures, followed by evaporating and phase separating at high temperatures. Applying the proposed approach a crude MgCl2 · 6H2O(s) sample can be purified to the level of Y b = 0.17% by only one crystallization process.

Solubilities and Modeling of Glycine in Mixed NaCl–MgCl2 Solutions in a Highly Concentrated Region

Electrolyte solution has an effect on growth and nonlinear optical properties of glycine crystals at certain conditions. The solubility of glycine in MgCl2–H2O solutions with molality from 0.5 to 3.5 was investigated by a dynamic method from (283.15 to 333.15) K. The solubilities of MgCl2·6H2O in glycine–water solution with molalities from 0.08 to 0.67 were also measured by the same method from (293.15 to 323.15) K. For model validation, the solubility of glycine in mixed NaCl–MgCl2 solutions was also measured. The solubilities of both glycine and MgCl2·6H2O solids were observed to increase with increasing temperature and concentration with respect to one another, acting as solutes. The OLI correlation with an existing model shows large errors in the solubility calculation for the glycine–NaCl–MgCl2–H2O system. A self-consistent model using a unified set of model parameters obtained by regressing the solubility of glycine in single salt systems was developed. The model can accurately predict the solubilit...

Hydrothermal dolomitization of the Bekhme formation (Upper Cretaceous), Zagros Basin, Kurdistan Region of Iraq: Record of oil migration and degradation

The common presence of oil seepages in dolostones is widespread in Cretaceous carbonate successions of the Kurdistan Region of Iraq. This integrated field, petrographic, chemical, stable C, O and Sr isotopes, and fluid inclusion study aims to link dolomitization to the origin and geochemical evolution of fluids and oil migration in the Upper Cretaceous Bekhme carbonates. Flux of hot basinal (hydrothermal) brines, which is suggested to have occurred during the Zagros Orogeny, resulted in dolomitization and cementation of vugs and fractures by coarse-crystalline saddle dolomite, equant calcite and anhydrite. The saddle dolomite and host dolostones have similar stable isotopic composition and formed prior to oil migration from hot (81–115°C) basinal NaCl–MgCl2–H2O brines with salinities of 18–22wt.% NaCl eq. The equant calcite cement, which surrounds and hence postdates saddle dolomite, has precipitated during oil migration from cooler (60–110°C) NaCl–CaCl2–H2O brines (14–18wt.% NaCl eq). The yellowish fluorescence color of oil inclusions in the equant calcite indicates that the oil had API gravity of 15–25° composition, which is lighter than present-day oil in the reservoirs (API of 10–17°). This difference in oil composition is attributed to oil degradation by the flux of meteoric water, which is evidenced by the low δ13C values (−8.5‰ to −3.9‰ VPDB) as well as by nil salinity and low temperature in fluid inclusions of late columnar calcite cement.This study demonstrates that linking fluid flux history and related diagenesis to the tectonic evolution of the basin provides important clues to the timing of oil migration, degradation and reservoir evolution.

Saddle dolomite and calcite cements as records of fluid flow during basin evolution: Paleogene carbonates, United Arab Emirates

Field observations indicate that tectonic compression, anticline formation and concomitant uplift events of marine Paleogene carbonates in eastern United Arab Emirates, which are related to the Zagros Orogeny, have induced brecciation, karstification, and carbonate cementation in vugs and along faults and fractures. Structural analysis, stable isotopes and fluid inclusion microthermometry are used to constrain the origin and geochemical evolution of the fluids. Fluid flow was related to two tectonic deformation phases. Initially, the flux of moderately 87Sr-rich basinal NaCl–MgCl2–H2O brines along reactivated deep-seated strike-slip faults have resulted in the precipitation of saddle dolomite in fractures and vugs and in dolomitization of host Eocene limestones (δ18OV-PDB −15.8‰ to −6.2‰; homogenization temperatures of 80–115 °C and salinity of 18–25 wt.% eq. NaCl). Subsequently, compression and uplift of the anticline was associated with incursion of meteoric waters and mixing with the basinal brines, which resulted in the precipitation of blocky calcite cement (δ18OV-PDB −22‰ to −12‰; homogenization temperatures of 60–90 °C and salinity of 4.5–9 wt.% eq. NaCl). Saddle dolomite and surrounding blocky calcite have precipitated along the pre- and syn-folding E–W fracture system and its conjugate fracture sets. The stable isotopes coupled with fluid-inclusion micro-thermometry (homogenization temperatures of ≤50 °C and salinity of <1.5 wt.% eq. NaCl) of later prismatic/dogtooth and fibrous calcites, which occurred primarily along the post-folding NNE–SSW fracture system and its conjugate fracture sets, suggest cementation by descending moderately 87Sr-rich, cool meteoric waters. This carbonate cementation history explains the presence of two correlation trends between the δ18OV-PDB and δ13CV-PDB values: (i) a negative temperature-dependent oxygen isotope fractionation trend related to burial diagenesis and to the flux of basinal brines, and (ii) positive brine-meteoric mixing trend. This integrated study approach allows better understanding of changes in fluid composition and circulation pattern during evolution of foreland basins.

Isopiestic Measurements of Water Activity for the NaCl–KCl–MgCl2–H2O Systems at 323.15 K

Water activity for binary KCl–H2O, NaCl–H2O and MgCl2–H2O, as well as two ternary NaCl–MgCl2–H2O and KCl–MgCl2–H2O, systems has been measured by using an isopiestic method at 323.15 K. The isopiestic results obtained show that the isopiestic composition lines of the NaCl–MgCl2–H2O system was found to obey the Zdanovskii rule, whereas the KCl–MgCl2–H2O system was observed to deviate slightly. The experimental water activities determined were applied to regress the parameters of the Pitzer model with a good agreement. The model with new parameters is validated by comparing water activity predictions with those given in the literature and not used in the parametrization process and calculating the solubility of the NaCl–MgCl2–H2O and KCl–MgCl2–H2O systems at various temperatures with the comparison of literature values.

Hydrocarbon fluid inclusions in the Argo salt, offshore Canadian Atlantic margin

Fluid inclusions hosted in rock salt from the Triassic Argo Formation in the Canadian Atlantic continental margin were studied to investigate the nature and origin of petroleum fluids in them. Inclusions were studied in two wells: Glooscap-C63 and Weymouth-A45. The pillow-shaped salt body intersected by the Glooscap-C63 well is autochthonous, and the salt is transparent and colorless compared with that in the allochthonous, canopy–diaper-shaped body cut by the Weymouth-A45 well which is translucent and buff-colored. Aqueous (AFI), petroleum (PFI), and heterogeneously trapped, mixed petroleum – aqueous (MFI) fluid inclusions were identified using transmitted and fluorescent microscopy, and representative samples were analyzed microthermometrically. Petroleum-bearing fluid inclusions (PFI and MFI) are more common and contain more concentrated petroleum phases in the allochthonous salts of Weymouth-A45 well. Based on microthermometric studies, the AFI and MFI in Glooscap-C63 salt mostly belong to NaCl–H2O and NaCl–H2O–petroleum systems, respectively; in contrast, those of Weymouth-A45 belong to NaCl–MgCl2–H2O and (or) NaCl–CaCl2–H2O and NaCl–MgCl2–H2O–petroleum and (or) NaCl–CaCl2–H2O–petroleum systems, respectively. Each of the AFI, PFI, and MFI types consists of different phases. The medians of Tf (freezing temperature), Tim (initial melting temperature), Te (Eutectic temperature), Tm (final melting (peritectic) temperature), and Th (homogenization temperature) in the AFI and MFI in the salts of Glooscap-C63 well are (−82, −75 °C), (−39, −38 °C), (−25, −24 °C), (−1.8, −3 °C), and (291, 287 °C), respectively. The corresponding medians for the Weymouth-A45 well are (−71, −78 °C), (−52, −52 °C), (−37, −38 °C), (−2.7, −3 °C), and (122, 20 °C), respectively. The median Th of PFI in Glooscap-C63 and Weymouth-A45 salts are 79 and 23 °C, respectively. The most probable source rocks for the petroleum are the shales of the Late Triassic – Early Jurassic Eurydice Formation which is widely distributed at depth underlying the Argo salt.

Prediction of the freezing point of multicomponent liquid refrigerant solutions

The freezing point is one of the most critical properties required to complete the mathematical formulation related to the transport phenomena involved in the immersion chilling and freezing (ICF) of foods. Unfortunately, data for ternary and higher order systems are scarce. The aim of this work was to verify the validity of an excess Gibbs energy model for predicting the freezing point of multicomponent mixtures of electrolytes and non-electrolytes, considering the processing conditions used in immersion chilling and freezing of foods. The extended UNIQUAC model was used. Data obtained from literature corresponding to freezing points of the ternary systems: NaCl–KCl–H2O, NaCl–CaCl2–H2O, NaCl–MgCl2–H2O and NaCl–EtOH–H2O, were compared with predicted values. The model accuracy was satisfactory, the highest absolute deviation being smaller than 1.71°C for the 378 data compared.

Petrographic, REE, fluid inclusion and stable isotope study of magnesite from the Upper Triassic Burano Evaporites (Secchia Valley, northern Apennines): contributions from sedimentary, hydrothermal and metasomatic sources

Sparry and microcrystalline magnesite are minor constituents of the Upper Triassic Burano Evaporite Formation of the northern Apennines in Italy. Petrography and geochemistry of magnesite suggest three modes of formation. (1) Evaporitic precipitation of stratified microcrystalline magnesite layers associated with sulfate and carbonate rocks. Most REE are below ICP-MS detection limits. δ18O is +20.2‰ (SMOW) and δ13C is –2.6‰ (PDB). (2) Hydrothermal infill of Fe-rich (9.78 wt% FeO) lenticular sparry magnesite. This type of magnesite is characterized by very low LREE concentrations, whereas HREEs are relatively high. The fluid inclusion composition is NaCl–MgCl2–H2O, salinity is ~30 wt% NaCl equiv., and total homogenization temperatures range from 204–309 °C; δ18O is +17.5‰ and δ13C is +1‰. (3) The partial or total replacement of dolostones by lenticular sparry magnesite. LREEs are lower in magnesite compared with the partly replaced dolostones. Magnesite yields δ18O and δ13C compositions of +17.3 to +23.6‰ and +0.5 to +1.4‰, respectively, whereas the partly replaced dolostones yield δ18O and δ13C values of +25.0 to +26.2 and +1.3 to +1.9, respectively. Complete replacement of dolostones produced massive lenticular sparry magnesite rock containing ooids and axe-head anhydrite relicts; LREEs are depleted compared to unaffected dolostones; δ18O and δ13C compositions range from +16.4 to +18.4‰ and +0.4 to +0.9‰, respectively. These data and the association between fracture-filling and replacive magnesite suggests a metasomatic system induced by hydrothermal circulation of hot and saline Mg-rich fluids. These processes probably occurred in the Oligocene–Miocene, when the Burano Formation acted as main detachment horizon for the Tuscan Nappe during the greenschist facies metamorphism of the Apuane complex. Thrusting over the Apuane zone produced large scale fluid flow focused at the Tuscan Nappe front. Sources of Mg-rich fluids were metamorphic reactions in the Apuane complex and dissolution of Mg-salts at the thrust front. Considering a maximum tectonic burial depth of 10 km, as inferred from the geometry of the chain, the pressure-corrected temperature of magnesite precipitation (380 to 400 °C) and the calculated fluid composition (δ18O=+13.3±1.2‰) are in the range of the published Apuane metamorphic temperatures (300–450 °C) and fluid compositions (δ18O=7–16‰). The results of this study support the hydrothermal-metasomatic model for the formation of sparry magnesite deposits at the expense of dolostone units involved in thrusting and low-grade metamorphism, as proposed for the Northern Graywacke Zone (Alps) and the Eugui deposit (western Pyrenees).

A New Predictive Equation for the Depression in Freezing Points of Multicomponent Aqueous Solutions Conforming to the Linear Isopiestic Relation

The linear isopiestic relation has been used together with a well-known thermodynamic equation to establish a new predictive equation for freezing point depression. This equation can provide predictions for multicomponent solutions conforming to the linear isopiestic relation using only information on the corresponding binary subsystems. The predictive capability of the equation has been tested by comparing with the experimental data at 25°C reported in the literature and particularly those of Pathwardhan and Kumar. The systems used are NaCl—MgCl2—H2O, NaCl—BaCl2—H2O, NaCl—CaCl2—H2O, LiCl—NaCl—H2O, LiCl—KCl—H2O, LiCl—CsCl—H2O, NaCl—KCl—H2O, and NaBr—KBr—H2O. The predictions of the two equations agree well with the experimental data although our new equation is, in general, better.

A new equation for predicting the density of multicomponent aqueous solutions conforming to the linear isopiestic relation

The linear isopiestic relation has been used together with well-known thermodynamic equations to establish a new simple predictive equation for density. This equation can provide the density for multicomponent solutions conforming to the linear isopiestic relation using only information on the corresponding binary sub-systems of equal water activity. No additional empirical parameters are involved. The predictive capability of the equation has been tested by comparison with the density measurements for the ternary systems NaCl–KCl–H2O, NaCl–CaCl2–H2O, KCl–CaCl2–H2O, NaCl–MgCl2–H2O, NaCl–Na2SO4–H2O, NaCl–MgSO4–H2O and NaBr–KCl–H2O and their corresponding binary subsystems over the whole experimental composition ranges at 298.15 K. The agreement between the predicted and measured densities is excellent over the entire experimental composition ranges.