Solubility Of H2O Research Articles

Experimental Simulation of Closed-System Degassing in the System Basalt–H2O–CO2–S–Cl

Magma degassing processes are commonly elucidated by studies of melt inclusions in erupted phenocrysts and measurements of gas discharge at volcanic vents, allied to experimentally constrained models of volatile solubility. Here we develop an alternative experimental approach aimed at directly simulating decompression-driven, closed-system degassing of basaltic magma in equilibrium with an H^C^O^S^Cl fluid under oxidized conditions (fO2 of 1·0^2· 4l og units above the Ni^NiO buffer). Synthetic experimental starting materials were based on basaltic magmas erupted at the persistently degassing volcanoes of Stromboli (Italy) and Masaya (Nicaragua) with an initial volatile inventory matched to the most undegassed melt inclusions from each volcano. Experiments were run at 25^400 MPa under super-liquidus conditions (11508C). Run product glasses and starting materials were analysed by electron microprobe, secondary ion mass spectrometry, Fourier transform infrared spectroscopy, Karl-Fischer titration, Fe 2þ /Fe 3þ colorimetry and CS analyser. The composition of the exsolved vapour in each run was determined by mass balance. Our results show that H2O/ CO2 ratios increase systematically with decreasing pressure, whereas CO2/S ratios attain a maximum at pressures of 100^300 MPa. S is preferentially released over Cl at low pressures, leading to a sharp increase in vapour S/Cl ratios and a sharp drop in the S/Cl ratios of glasses. This accords with published measurements of volatile concentrations in melt inclusion and groundmass glasses at Stromboli (and Etna). Experiments with different S abundances show that the H2O and CO2 contents of the melt at fluid saturation are not affected. The CO2 solubility in experiments using both sets of starting materials is well matched to calculated solubilities using published models. Models consistently overestimate H2O solubilities for the Stromboli-like composition, leading to calculated vapour compositions that are more CO2-rich and calculated degassing trajectories that are more strongly curved than observed in experiments. The difference is less acute for the Masaya-like composition, emphasizing the important compositional dependence of solubility and melt^ vapour partitioning. Our novel experimental method can be readily extended to other bulk compositions.

The Process to Recover Soda Ash from Mining Solution in a Pilot Plant

The process to recover soda ash from mining solution is combined CO2stripping with falling film evaporation, and the stripping operation is the key step in the process, the processing installations include a CO2stripping tower, falling film evaporators and other accessories. The stripping and combined operation(linking CO2stripping with falling film evaporation) are implemented to examine tower operational conditions and ascertain how to efficiently concentrate mining solution, respectively. As a result, after the better design scheme(17-meter height packing) is evidently proposed and the process design is also favorably optimized, such as diminishing equipment sizes in a following industrial scale. Besides, the work also analyzes the solubility of Na2CO3and NaHCO3in H2O and discusses its probable equilibrium in the operation.

Structure and Dynamics of Neat and CO2-Reacted Ionic Liquid Tetrabutylphosphonium 2-Cyanopyrrolide

Results of molecular dynamics simulations are reported in which the structure and dynamics of the reacted and unreacted forms of the task-specific ionic liquid (TSIL) tetrabutylphosphonium 2-cyanopyrrolide were computed. This particular ionic liquid is one of several newly discovered TSILs containing aprotic heterocyclic anions designed specifically for CO2 capture. The physical properties, liquid structure, and dynamics of the ionic liquid were computed as a function of extent of reaction with CO2. Translational and rotational dynamics showed little change upon reaction with CO2, in sharp contrast to traditional TSILs and consistent with experimental viscosity measurements. It is shown that this is due to the failure of a hydrogen-bond network to form upon reaction with CO2. The Henry’s law constants for the physical solubility of CO2, N2, O2, and H2O were computed for the unreacted TSIL and found to be comparable to values observed with other ionic liquids. In the reacted state, the solubility of CO2, N...

Petrolog3: Integrated software for modeling crystallization processes

This paper introduces Petrolog3, software for modeling (1) fractional and equilibrium crystallization, (2) reverse fractional crystallization at variable pressure, melt oxidation state and melt H2O contents, and (3) postentrapment reequilibration of melt inclusions in olivine. Petrolog3 offers an algorithm that allows calculations with a potentially unlimited number of (1) mineral-melt equilibrium models for major and trace elements and (2) models describing melt physical parameters such as density and viscosity, melt oxidation state, and solubility of fluid components in silicate melts. The current version of the software incorporates 46 mineral-melt equilibrium models for 8 minerals; 3 models describing distribution of trace elements between minerals and melt; 4 models of melt oxidation state; 1 model for H2O solubility in silicate melts; and 4 models describing melt density and viscosity. The idea behind the program is to provide the community of igneous petrologists and geochemists with a user-friendly interface for using any combinations of available mineral-melt equilibrium models for computer simulation of the crystallization process.

C–O–H–S fluids and granitic magma: how S partitions and modifies CO2 concentrations of fluid-saturated felsic melt at 200 MPa

Hydrothermal volatile-solubility and partitioning experiments were conducted with fluid-saturated haplogranitic melt, H2O, CO2, and S in an internally heated pressure vessel at 900°C and 200 MPa; three additional experiments were conducted with iron-bearing melt. The run-product glasses were analyzed by electron microprobe, FTIR, and SIMS; and they contain ≤0.12 wt% S, ≤0.097 wt% CO2, and ≤6.4 wt% H2O. Apparent values of log fO2 for the experiments at run conditions were computed from the [(S6+)/(S6++S2−)] ratio of the glasses, and they range from NNO −0.4 to NNO + 1.4. The C–O–H–S fluid compositions at run conditions were computed by mass balance, and they contained 22–99 mol% H2O, 0–78 mol% CO2, 0–12 mol% S, and <3 wt% alkalis. Eight S-free experiments were conducted to determine the H2O and CO2 concentrations of melt and fluid compositions and to compare them with prior experimental results for C–O–H fluid-saturated rhyolite melt, and the agreement is excellent. Sulfur partitions very strongly in favor of fluid in all experiments, and the presence of S modifies the fluid compositions, and hence, the CO2 solubilities in coexisting felsic melt. The square of the mole fraction of H2O in melt increases in a linear fashion, from 0.05 to 0.25, with the H2O concentration of the fluid. The mole fraction of CO2 in melt increases linearly, from 0.0003 to 0.0045, with the CO2 concentration of C–O–H–S fluids. Interestingly, the CO2 concentration in melts, involving relatively reduced runs (log fO2 ≤ NNO + 0.3) that contain 2.5–7 mol% S in the fluid, decreases significantly with increasing S in the system. This response to the changing fluid composition causes the H2O and CO2 solubility curve for C–O–H–S fluid-saturated haplogranitic melts at 200 MPa to shift to values near that modeled for C–O–H fluid-saturated, S-free rhyolite melt at 150 MPa. The concentration of S in haplogranitic melt increases in a linear fashion with increasing S in C–O–H–S fluids, but these data show significant dispersion that likely reflects the strong influence of fO2 on S speciation in melt and fluid. Importantly, the partitioning of S between fluid and melt does not vary with the (H2O/H2O + CO2) ratio of the fluid. The fluid-melt partition coefficients for H2O, CO2, and S and the atomic (C/S) ratios of the run-product fluids are virtually identical to thermodynamic constraints on volatile partitioning and the H, S, and C contents of pre-eruptive magmatic fluids and volcanic gases for subduction-related magmatic systems thus confirming our experiments are relevant to natural eruptive systems.

CO2 transport–Depressurization, heat transfer and impurities

Abstract Detailed knowledge on depressurization, heat transfer and impurities in CO2 pipelines has shown to be important for safe and cost effective design of CCS chains. The aim of this paper is to present the latest results on the modelling and experimental verification of these aspects. A newly developed CO2 module in the flow engineering software OLGA from SPT Group has been used to model experimental results on depressurization, which is a two-phase transient flow with evaporation and Joule-Thomson cooling. A visual comparison of model and experiments in PT-diagrams showed that the new CO2 module in OLGA captures the depressurization behaviour reasonably well, but still has room for improvement. Heat transfer coefficients for heat transfer from aqueous surroundings to cold CO2 in a pipeline segment was measured in a dedicated rig. A thin layer of ice formation was observed on the bottom of the pipeline. The overall heat transfer coefficient at the experimental conditions has been calculated to be 45.0 W/m2K, where the outer heat transfer coefficient was 162.3 W/m2K, and the inner heat transfer coefficient 166.2 W/m2K. 46 Experiments and modelling of H2O solubility in vapour and liquid CO2 were performed for verifying the VLHE-behaviour at low H2O concentrations down to −50 °C. Hydrafact’s model HWHyd 2.2 model predicted the experimental result with average 8.2% deviation. Hence, the model can be used for setting hydrate formation limited H2O specifications in transport of pure CO2.

The H2O solubility of alkali basaltic melts: an experimental study

Experiments were conducted to determine the water solubility of alkali basalts from Etna, Stromboli and Vesuvius volcanoes, Italy. The basaltic melts were equilibrated at 1,200°C with pure water, under oxidized conditions, and at pressures ranging from 163 to 3,842 bars. Our results show that at pressures above 1 kbar, alkali basalts dissolve more water than typical mid-ocean ridge basalts (MORB). Combination of our data with those from previous studies allows the following simple empirical model for the water solubility of basalts of varying alkalinity and fO2 to be derived: $$ {\text{H}}_{ 2} {\text{O}}\left( {{\text{wt}}\% } \right) = {\text{ H}}_{ 2} {\text{O}}_{\text{MORB}} \left( {{\text{wt}}\% } \right) + \left( {5.84 \times 10^{ - 5} *{\text{P}} - 2.29 \times 10^{ - 2} } \right) \times \left( {{\text{Na}}_{2} {\text{O}} + {\text{K}}_{2} {\text{O}}} \right)\left( {{\text{wt}}\% } \right) + 4.67 \times 10^{ - 2} \times \Updelta {\text{NNO}} - 2.29 \times 10^{ - 1} $$ where H2OMORB is the water solubility at the calculated P, using the model of Dixon et al. (1995). This equation reproduces the existing database on water solubilities in basaltic melts to within 5%. Interpretation of the speciation data in the context of the glass transition theory shows that water speciation in basalt melts is severely modified during quench. At magmatic temperatures, more than 90% of dissolved water forms hydroxyl groups at all water contents, whilst in natural or synthetic glasses, the amount of molecular water is much larger. A regular solution model with an explicit temperature dependence reproduces well-observed water species. Derivation of the partial molar volume of molecular water using standard thermodynamic considerations yields values close to previous findings if room temperature water species are used. When high temperature species proportions are used, a negative partial molar volume is obtained for molecular water. Calculation of the partial molar volume of total water using H2O solubility data on basaltic melts at pressures above 1 kbar yields a value of 19 cm3/mol in reasonable agreement with estimates obtained from density measurements.

ChemInform Abstract: Aromatic Nucleophilic Substitution. Part 3. Preparation of Novel 9-Oxo- 9H-thioxanthene- and 9-Oxo-9H-xanthenedicarboximides and - dicarboxylates.

By aromatic nucleophilic substitution followed by intramolecular acylation, 9-oxo-9H-thioxanthene- and 9-oxo-9H-xanthene-dicarboximides were prepared from nitro- or chlorophthalimides and the dianions of thiosalicylic and salicylic acids (Scheme). The 9-oxo-9H-thioxanthene-3,4-dicarboximides were converted to 9-oxo-9H-thioxanthene-3,4-dicarboxylic-acid derivatives such as anhydride, esters, and further imides. Some of these derivatives proved to be excellent photosensitizers with special properties such as liquid aggregation form, H2O solubility, solubility in lipophilic organic solvents and polymers, or bathochromic shifts of the absorption wavelengths.

Aqueous fluids at elevated pressure and temperature

AbstractThe general major component composition of aqueous fluids at elevated pressure and temperature conditions can be represented by H2O, different non‐polar gases like CO2 and different dissolved metal halides like NaCl or CaCl2. At high pressure, the mutual solubility of H2O and silicate melts increases and also silicates may form essential components of aqueous fluids. Given the huge range of P–T–x regimes in crust and mantle, aqueous fluids at elevated pressure and temperature are highly variable in composition and exhibit specific physicochemical properties. This paper reviews principal phase relations in one‐ and two‐component fluid systems, phase relations and properties of binary and ternary fluid systems, properties of pure H2O at elevated P–T conditions, and aqueous fluids in H2O–silicate systems at high pressure and temperature. At metamorphic conditions, even the physicochemical properties of pure water substantially differ from those at ambient conditions. Under typical mid‐ to lower‐crustal metamorphic conditions, the density of pure H2O is , the ion product Kw = 10−7.5 to approximately 10−12.5, the dielectric constant ε = 8–25, and the viscosity η = 0.0001–0.0002 Pa sec compared to , Kw = 10−14, ε = 78 and η = 0.001 Pa sec at ambient conditions. Adding dissolved metal halides and non‐polar gases to H2O significantly enlarges the pressure–temperature range, where different aqueous fluids may co‐exist and leads to potential two‐phase fluid conditions under must mid‐ to lower‐crustal P–T conditions. As a result of the increased mutual solubility between aqueous fluids and silicate melts at high pressure, the differences between fluid and melt vanishes and the distinction between fluid and melt becomes obsolete. Both are completely miscible at pressures above the respective critical curve giving rise to so‐called supercritical fluids. These supercritical fluids combine comparably low viscosity with high solute contents and are very effective metasomatising agents within the mantle wedge above subduction zones.

Lipid- and water-soluble bilirubins

Novel bilirubin analogs with two nonionic, water-solubilizing polyethyleneglycol (PEG) β-substituents of varying chain length on the lactam ring of each dipyrrinone were synthesized. In contrast to bilirubin, which is insoluble in CH3OH and in H2O at pH 7 but somewhat soluble in CHCl3 (~1 mM), the PEGylated rubins are soluble in all three solvents, with H2O solubility increasing with increasing number of ethyleneglycol units in the PEG chain(s). Vapor pressure osmometry indicates that, like bilirubin, they are monomeric in CHCl3 and in CH3OH. Nuclear magnetic resonance (NMR) studies indicate that their most stable structure in these solvents and in H2O has the 4Z,15Z configuration that is bent into a ridge-tile shape with the pigment’s dipyrrinones engaged in intramolecular hydrogen bonding to the propionic acid carboxyl groups. Aqueous pK a values for the intramolecularly hydrogen-bonded carboxyl groups of these compounds, determined by vacuum-assisted multiplexed capillary electrophoresis in H2O–CH3OH mixtures followed by Yesuda-Shedlovsky extrapolations to pure H2O, were found to be 4.9, as previously determined by NMR titrations for mesobilirubin-XIIIα.

Solubility of C-O-H mixturesin natural melts: new experimental data and application range of recent models

The effect of pressure, temperature, and melt composition on CO2 and H2O solubilities in aluminosilicate melts, coexisting with CO2-H2O fluids, is discussed on the basis of previously published and new experimental data. The datasets have been chosen so that CO2 and H2O are the main fluid components and the conclusions are only valid for relatively oxidizing conditions. The most important parameters controlling the solubilities of H2O and CO2 are pressure and composition of melt and fluid. On the other hand, the effect of temperature on volatile solubilities is relatively small. At pressures up to 200 MPa, intermediate compositions such as dacite, in which both molecular CO2 and carbonate species can be dissolved, show higher volatile solubilities than rhyolite and basalt. At higher pressures (0.5 to 1 GPa), basaltic melts can incorporate higher amounts of carbon dioxide (by a factor of 2 to 3) than rhyolitic and dacitic melts. Henrian behavior is observed only for CO2 solubility in equilibrium with H2O-CO2 fluids at pressures <100 MPa, whereas at higher pressures CO2 solubility varies nonlinearly with CO2 fugacity. The positive deviation from linearity with almost constant CO2 solubility at low water activity indicates that dissolved water strongly enhances the solubility of CO2. Water always shows non-Henrian solubility behavior because of its complex dissolution mechanism (incorporation of OH-groups and H2O molecules in the melt). The model of Newman and Lowenstern (2002), in which ideal mixing between volatiles in both fluid and melt phases is assumed, reproduces adequately the experimental data for rhyolitic and basaltic compositions at pressures below 200 MPa but shows noticeable disagreement at higher pressures, especially for basalt. The empirical model of Liu et al. (2004) is applicable to rhyolitic melts in a wide range of pressure (0-500 MPa) and temperature (7001200°C) but cannot be used for other melt compositions. The thermodynamic approach of Papale (1999) allows to calculate the effect of melt composition on volatile solubilities but needs an update to account for more recent experimental data. A disadvantage of this model is that it is not available as a program code. The review indicates a crucial need of new experimental data for scarcely investigated field of pressures and fluid compositions and new models describing evident non-ideality of H-C-O fluid solubility in silicate melts at high pressures.

Increasing antitumor activity in vivo by enhancing acridine dimer solubility with salt preparations

The potent activities of many anticancer agents have been demonstrated by in vitro assays. However, their poor solubility may result in diminishing anticancer activities in vivo. Previously, we synthesized a series of bisacridine derivatives shown to be potent in cytotoxicity and DNA intercalating activity in vitro. Initially, the compound 1, (N-(6-chloro-2-methoxy-acridin-9-yl)-N′-[3-(6-chloro-2-methoxy-acridin-9-ylamino)-propyl]-propane-1,3-diamine), is insoluble in polar solvent and does not reveal antihuman COLO 205 solid-tumor activity in vivo. To enhance its solubility, three salt forms (CH3COOH, CH3SO3H, and CF3COOH) of compound 1 were synthesized and their solubility was found to be greatly improved compared with that of the free base. Among these salts, the compound 1 · (tris)acetate salt has shown good solubility in H2O and 2.5% Cremophor (v/v) and demonstrated anti-COLO205 solid-tumor activity in vivo.

Divergent Dendronization of Deep‐Cavity Cavitands to Tune Host Solubility

AbstractResorcinarene‐based deep‐cavity cavitands (DCCs) are useful components in supramolecular chemistry because their extended cavity enables the encapsulation of relatively large guests. To provide H2O solubility, they have been modified with hydroxyl functionalized dendrons. This has been carried out by the divergent dendronization of aliphatic poly(ester) dendrons through the third dendritic generation. The resultant macromolecule demonstrated the desired H2O solubility.

Kieserite Solubility in the Aqueous FeCl3 + MgCl2 + HCl System between (338 and 378) K

Kieserite (MgSO4·H2O) solubility was measured at temperatures between (338 and 378) K, FeCl3 concentrations of 1.0 mol·kg−1, MgCl2 concentrations between (1.1 and 3) mol·kg−1, and HCl concentrations between (0.5 and 2.3) mol·kg−1. These conditions are of interest because of their relevance for processes designed to extract nickel from oxide ores by atmospheric leaching in mixed sulfate−chloride solutions. Experimental data were compared with model predictions generated by use of OLI Software’s mixed solvent electrolyte (MSE) model. Model predictions for MgSO4·H2O solubility were found to match experimental results with an average absolute deviation of ± 0.09 mol·kg−1 and an average absolute relative deviation of 11.1 %. The ability of the model to accurately predict solubility trends in solutions not used in the development of model parameters validates the model.

Solubility of H2O and CO2 in ultrapotassic melts at 1200 and 1250 C and pressure from 50 to 500 MPa

The solubility of H2O-CO2 fluids in a synthetic analogue of a phono-tephritic lava composition from Alban Hills (Central Italy) was experimentally determined from 50 to 500 MPa, at 1200 and 1250 °C. Contents of H2O and CO2in experimental glasses were determined by bulk-analytical methods and FTIR spectroscopy. For the quantification of volatile concentrations by IR spectroscopy, we calibrated the absorption coefficients of water-related and carbon-related bands for phono-tephritic compositions. The determined absorption coefficients are 0.62 ± 0.06 L/(mol·cm) for the band at ~4500 cm−1 (OH groups) and 1.02 ± 0.03 L/(mol·cm) for the band at ~5200 cm−1 (H2O molecules). The coefficient for the fundamental OH-stretching vibration at 3550 cm−1 is 63.9 ± 5.4 L/(mol·cm). CO2 is bound in the phono-tephritic glass as CO32− exclusively; its concentration was quantified by the peak height of the doublet near the 1500 cm−1 band with the calibrated absorption coefficient of 308 ± 110 L/(mol·cm). Quench crystals were observed in glasses with water contents exceeding 6 wt% even when using a rapid-quench device, limiting the application of IR spectroscopy for water-rich glasses. H2O solubility in the ultrapotassic melts (7.52 wt% K2O) as a function of pressure is similar to the solubility in basaltic melts up to 400 MPa (~8 wt%) but is higher at 500 MPa (up to 10.71 wt%). At 500 MPa and 1200 °C, the CO2 capacity of the phono-tephritic melt is about 0.82 wt%. The high CO2 capacity is probably related to the high K2O content of the melt. At both 200 and 500 MPa, the H2O solubility shows a non linear dependence on XH2Of in the whole XH2Of range. The variation of CO2 solubility with XCO2f displays a pronounced convex shape especially at 500 MPa, implying that dissolved H2O promotes the solubility of CO2. Our experimental data on CO2 solubility indicate that the interaction between phono-tephritic magma and carbonate rocks occurring in the Alban Hills magmatic system may result in partial dissolution of CO2 from limestone into the magma. However, although the CO2 solubility in phono-tephritic melts is relatively high compared to that in silicic to basaltic melts, the capacity for assimilation of limestone without degassing is nevertheless limited to <1 wt% at the P - T conditions of the magma chamber below Alban Hills.

Silicate melt properties and volcanic eruptions

Knowledge about the properties of silicate melts is needed by volcanologists and petrologists to evaluate the dynamics of volcanic eruptions and magmatic processes. These properties include the solubility and diffusivity of volatile components in silicate melts, silicate melt viscosity, and the fragmentation condition. Data and models of each property are reviewed and assessed. For rhyolitic melts many properties are sufficiently well known to allow realistic modeling of volcanic and magmatic processes. One interesting example is the role of speciation in the solubility and diffusivity of H2O and CO2. Even though both H2O and CO2 are present in silicate melts as at least two species, the complexity in the solubility and diffusion behavior of H2O and the simplicity of CO2 are due to differences in the speciation reaction: For the H2O component the stoichiometric coefficient is one for one hydrous species (molecular H2O) but is two for the other hydrous species (OH) in the species interconversion reaction, whereas for CO2 the stoichiometric coefficients for all carbon species are one. The investigation of the species reaction not only helps in understanding the solubility and diffusion behavior, but the reaction among the hydrous species also serves as a geospeedometer (cooling rate indicator) for hydrous rhyolitic pyroclasts and glass and provides a method to infer viscosity. For melts other than rhyolite, a preliminary description of their properties is also available, but much more experimental and modeling work is necessary to quantify these properties more accurately.

Controlled Release of Volatile Aldehydes and Ketones from Dynamic Mixtures Generated by Reversible Hydrazone Formation

AbstractDelivery systems generated by reversible hydrazone formation from hydrazine derivatives (see Fig. 1) and carbonyl compounds in H2O efficiently increase the long‐lastingness of volatile aldehydes and ketones (R1R2CO) in various perfumery applications. The hydrazones are usually obtained in an (E) configuration at the imine double bond (NHNC) and, in the case of aliphatic acylhydrazones R′CONHNCR1R2 (R′=alkyl), as syn and anti conformers with respect to the amide bond (CONHN). An average free‐energy barrier of ca. 78 kJ/mol was determined for the amide‐bond rotation by variable‐temperature 1H‐NMR measurements (Fig. 2). In the presence of H2O, the hydrazone formation is entirely reversible, reaching an equilibrium composed of the hydrazine derivative, the carbonyl compound, and the corresponding hydrazone. Kinetic measurements carried out by UV/VIS spectroscopy showed that the same equilibrium was reached for the formation and hydrolysis of the hydrazone. Rate constants are strongly pH‐dependent and increase with decreasing pH (Table 1). The influence of the hydrazine structure on the rate constants is less pronounced than the pH effect, and the presence of surfactants reduces the rate of equilibration (Tables 1 and 3). The full reversibility of the hydrazone formation allows to prepare dynamic mixtures by simple addition of a hydrazine derivative to several carbonyl compounds. Dynamic headspace analysis on dry cotton showed that the presence of a hydrazine derivative significantly increased the headspace concentrations of the different carbonyl compounds as compared to the reference sample without hydrazine (Table 4). The release of the volatiles was found to be efficient for fragrances with high vapor pressures and low H2O solubility. Furthermore, a special long‐lasting effect was obtained for the release of ketones. The simplicity of generating dynamic mixtures combined with the high efficiency for the release of volatiles makes these systems particularly interesting for practical applications and will certainly influence the development of delivery systems in other areas such as the pharmaceutical or agrochemical industry.

Calcium carbonate supersaturation and precipitation in Chinese mitten crab (Eriocheir japonica sinensis) larval ponds in China: Mass mortality, crystal form analysis, and safety saturation index

In recent years, mass mortalities of Chinese mitten crab (Eriocheir japonica sinensis) larvae have been reported in several crab culture regions in China and have resulted in great economic losses. The mass mortality usually occurs in seawater ponds in the afternoon of sunny days when water color suddenly changes from dark green or brown to cloudy white or light yellow, and mineral precipitate occurs. Moribund and dead larvae are typically covered with debris. A series of experiments was conducted to examine the cause of precipitation and mass mortality of crab larvae. Analysis of the precipitate from ponds with mass mortalities showed that CaCO3 was the main component of the precipitate, accounting for 70.8% of the total weight. In an animal experiment, mortalities were observed within 48 h in all groups with CaCO3 precipitate, and generally increased as pH and CaCO3 saturation rates increased. Mortalities in groups with CaCO3 precipitate were greater than those in groups without CaCO3 precipitate (P≤0.05). All larvae in groups with CaCO3 precipitate sank to the bottom of the beaker within 48 h. The animal experiment also showed that increased pH (up to 9.4) alone without CaCO3 precipitate did not result in larval mortality within 48 h. Results from the present investigation indicate that mass mortalities of the crab larvae are caused by CaCO3 supersaturation and rapid precipitation possibly triggered by increased pH as a result of intensive photosynthesis of phytoplankton in the seawater ponds. By comparing mean Ca2+ and CO32− ionic product obtained at the equilibrium with solubility product constants for various CaCO3 crystal forms, it appears that CaCO3·H2O is the main CaCO3 form. Based on the CaCO3·H2O solubility product constant and our field investigations, we suggest that CaCO3·H2O saturation indices of 2.5 and below be considered safe and 3.4 as warning signal for CaCO3 precipitation. Since several factors may cause CaCO3 supersaturation and precipitation in crab larval ponds, preventive measures should be implemented to stabilize pH and reduce the CaCO3 saturation rate.

Melt pockets in phenocrysts and decompression rates of silicic magmas before fragmentation

A new method is presented to estimate the decompression rate of silicic magma prior to fragmentation and is applicable to rates of 1–100 kPa/s. This method uses the remaining concentrations of H2O and CO2 in bubble‐free cylindrical melt (now glass) pockets in phenocrysts that are connected to the surrounding bubbly melt. These melt pockets are common in volcanic rocks. During magma ascent, bubbles grow in the surrounding melt, and the concentrations of dissolved H2O and CO2 decrease, establishing a boundary condition of low volatile concentration at the outlet of the melt pocket. In turn, volatiles diffuse from the melt pocket into the surrounding bubbly magma and form a gradient that is time dependent. The volatile concentration at the inner limit of the melt pocket likewise diminishes with time. Knowing the diffusivity and solubility of H2O and CO2 permits the remaining H2O and CO2 contents to be estimated for different decompression rates using diffusion equations. We apply this approach to the measured H2O and CO2 contents in quartz‐hosted melt pockets in pumice from the phreatomagmatic 26.5 ka Oruanui eruption, Taupo, New Zealand. A decompression rate of 1–7 kPa/s (∼5–35 cm/s) was obtained for Oruanui magma.

Solubility of corundum + kyanite in H2O at 700°C and 10 kbar: evidence for Al‐Si complexing at high pressure and temperature

AbstractThe solubility of the assemblage corundum + kyanite in H2O was determined at 700°C and 10 kbar, using a piston‐cylinder apparatus and rapid‐quench/fluid‐extraction techniques. Weighted mean concentrations of total Al and Si were 5.80 ± 0.03 mmol kg−1 H2O and 0.308 ± 0.003 mol kg−1 H2O, respectively (1σ errors). The Al concentration is nearly five times higher than that of corundum solubility in pure H2O. This difference is interpreted to arise from complexing between Si and Al to form HAlSiO4,aq species. Charged or more polymerized species are also possible, but their abundance cannot be constrained based on these experiments. Assumption of a single aqueous aluminosilicate complex permits calculation of the thermodynamic consequences of Al‐Si interaction in high‐pressure fluids, as well as phase diagrams for the system Al‐Si‐O‐H. Formation of Al‐Si complexes leads to a large increase in dissolved Al with increasing Si in solution, such that Al concentration in equilibrium with kyanite + quartz is predicted to be 7.1 mmolal, higher than with kyanite + corundum. The elevated concentration of Si in deep‐crustal and mantle aqueous fluids suggests that Al must readily be dissolved and transported by Al‐Si complexing in high‐pressure metamorphic and metasomatic environments. The results provide a simple explanation for the common observation of kyanite + quartz segregations in eclogites and Barrovian metamorphic rocks.