Dilute KCl Research Articles

Thermodynamically Traceable Calorimetric Results for Dilute Aqueous Potassium Chloride Solutions at Temperatures from 273.15 to 373.15 K. Part 2. The Quantities Associated with the Partial Molar Heat Capacity

In previous articles (Partanen J. Chem. Eng. Data 2019, 64, 16−33 and Partanen J. Chem. Eng. Data 2019, 64, 2519–2535), we presented traceable and transparent two-parameter Hückel equations (with parameters B and b1) for the activity coefficients of the salt and for the osmotic coefficients of water in aqueous KCl solutions in the temperature range of 273.15–383.15 K. The latter article is the first part (Part 1) of the calorimetric study. We showed in these articles that our equations for these solutions explain within experimental error the literature data on almost all thermodynamic quantities including the partial molar enthalpies at least up to a molality of 0.2 mol·kg–1 and up to 373 K. In this model, parameter B is regarded as a constant but parameter b1 has a quadratic temperature dependence. No calorimetric data were needed in the parameter estimation. In the second part (Part 2) of the calorimetric study, now, the results obtained for the heat capacity quantities of KCl (aq.) are considered. We show here that all heat capacity literature available for KCl solutions at least up to 0.5 mol·kg–1 is possible to explain within experimental error using exactly the same Hückel equations as those considered previously in our studies for dilute KCl solutions from 273 to 373 K. Because of the success of the used model, we supplement the existing thermodynamic tables with new values for the relative apparent and partial molar heat capacities for KCl solutions. It is likely that the new tables contain the most reliable values available for these heat capacity quantities.

Improving the safety of high-concentration potassium chloride injection

ObjectivesSerious adverse effects, including arrhythmia and cardiac arrest, result from rapid intravenous high concentration of potassium chloride (KCl). We aimed to eliminate prescription of undiluted KCl and encourage dilution of...

Thermodynamically Traceable Calorimetric Results for Dilute Aqueous Potassium Chloride Solutions at Temperatures from (273.15 to 373.15) K. Part 1. The Quantities Associated with the Partial Molar Enthalpy

In our previous study (Partanen, J. I.; Partanen, L. J.; Vahteristo, K. P., J. Chem. Eng. Data 2019, 64, 16–33), we presented a fully traceable two-parameter Huckel equation with parameters B and b1 for activity and osmotic coefficients in dilute KCl(aq) in the temperature range of (273.15 to 383.15) K. This equation applies within experimental error to almost all thermodynamic data in the literature at least up to a molality of 0.2 mol·kg–1. In our Huckel model, parameter B is treated as a constant, whereas parameter b1 depends quadratically on the temperature. In the present study, the same model is applied to the molar enthalpies of the components in KCl solutions. No new parameter estimations are necessary for the treatment of these calorimetric data. We also extend now the previous enthalpy results for dilute NaCl solutions (see Partanen, J. I.; Partanen, L. J.; Vahteristo, K. P., J. Chem. Eng. Data 2017, 62, 2717–2632) up to 373 K because in that study the treatment of calorimetric data was limited ...

Traceable Thermodynamic Quantities for Dilute Aqueous NaCl Solutions at Temperatures from (353.15 to 383.15) K and for Dilute Aqueous KCl Solutions from (273.15 to 383.15) K

We present fully traceable two-parameter Hückel equations with parameters B and b1 for the activity coefficient of sodium chloride and for the osmotic coefficient of water in aqueous NaCl solutions at temperatures from (353.15 to 383.15) K. In our most successful parametrization of these equations, parameter B is treated as a constant whereas b1 is a quadratic function of the temperature. The new calculations extend the tables presented up to 353.15 K in our previous study (Partanen, J. I.; Partanen, L. J.; Vahteristo, K. P. J. Chem. Eng. Data 2017, 62, 2617–2632), showing that our Hückel equations apply up to 383.15 K. We also present fully traceable activity quantities from (273.15 to 383.15) K for dilute KCl solutions. Our equations apply to these solutions at least up to a molality of 0.2 mol·kg–1. This article contains the most important new test results of the Hückel equations, where the literature data have been obtained by direct and isopiestic vapor measurements and boiling-point determinations at various pressures. In forthcoming studies, the test results obtained using these equations from KCl solutions will be published for the existing calorimetric data. On the basis of the extensive testing of our models against the experimental data available, the new tables contain the most reliable values of activity and osmotic coefficients for dilute NaCl and KCl solutions published so far. Finally, we report vapor pressures of water in NaCl and KCl solutions above 383 K up to 473 K. These values are obtained with a new and simplified parametrization of the Hückel equation, and our tests show that the parametrization applies well up to a molality of 6 mol·kg–1 in both cases at the high temperatures.

Efficient Electrocatalytic Reduction of Carbon Dioxide in 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate and Water Mixtures

The catalytic activity of room-temperature ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) for carbon dioxide (CO2) reduction is reported on a polycrystalline silver electrode as a function of the water content and solution pH. The optimal aqueous dilution was determined to be ca. 10% (v/v), resulting in a reduction of the overpotential required to reduce CO2 in [EMIM][OTf] by 400 mV. The reduction process and products are largely insensitive to pH. CO2 reduction in [EMIM][OTf] with 10% 0.1 M NaHCO3 is achieved with high selectivity for CO with 93.0 ± 4.6% Faradaic efficiency. Hydrogen evolution reaction (HER) is suppressed in the range of neat [EMIM][OTf] (500 ppm water content) to a [EMIM][OTf]/H2O mixture of 10% water content. Conductivity and viscosity of the [EMIM][OTf]/H2O mixture suggest that the ionic liquid ion pair fully dissociates, analogous to dilute KCl solution, where each ion is completely hydrated by water molecules.

A Comparison of Diffusion-Conductimetric and Distillation-Titration Methods in Analyzing Ammonium- and Nitrate-Nitrogen in the KCl-Extracts of Georgia Soils

ABSTRACTSoil mineral (or inorganic) nitrogen (SMN), which primarily exists as exchangeable and soluble ammonium (NH4+) and the nitrate (NO3−) ions, represents readily available nitrogen for plant growth. Over the years a 2M potassium chloride (KCl) solution has become the extraction solution of choice for extracting SMN. In the research and service laboratories, either distillation-titration method (DTM) or colorimetric method (CM) is virtually the standard to measure NH4+- and NO3−-N in the 2M KCl soil extracts. However, being a time-consuming and labor intensive method, DTM generally has a very low throughput. Likewise, CM is affected by interferences from pH variation, color, turbidity, presence of organic species, and some other constituents in the extracts. In contrast, diffusion conductivity method (DCM) is a less expensive and high throughput one, which is also relatively free from common interferences. In this study, we, therefore, compared the extraction efficiency of various KCl concentrations and performance of diffusion conductivity method (DCM) with DTM in measuring NH4+-N and NO3−-N in KCl extracts of 32 agricultural soils of Georgia. A 0.2M KCl solution extracted statistically similar amounts of NH4+-N and NO3−-N as did 2M KCl, suggesting that a 10-fold dilute KCl solution than the standard 2M KCl might be good enough to extract and estimate the most of SMN. For the analyses of NH4+- and NO3−-N in the KCl extracts, the DCM produced results statistically similar to those produced by DTM. The deviation between the results given by DCM and DTM was no more than ±10%. Thus, DCM appears to be an attractive alternative to the labor intensive and time-consuming DTM for measuring NH4+- and NO3−-N in the KCl extract of soils in the research and service laboratories.

Crystallinity and surface state of cellulose in wet ball‐milling process

ABSTRACTWe report the effect of wet ball‐milling process under mild neutral salt conditions on the alteration of crystallinity and surface state of microcrystalline cellulose (MC). The ball‐milling experiments were performed when the MC was immersed in H2O, NaCl aqueous solution, and KCl aqueous solution. Two collation groups, i.e., MC immersed in H2O2 and nonimmersed MC were additionally investigated for comparison. Except when H2O2 was present, the highest decrease in the cellulose crystallinity index (CI) was observed in dilute KCl. On the other hand, the CI of wet‐milled MC/NaCl was greater than that of the wet‐milled MC/H2O, however, still lower than that of the non‐immersed MC. XPS results showed that the carbonization progressed in dry‐milled MC and wet‐milled MC/NaCl surfaces. Though, the surface oxidization progressed in wet‐milled MC/H2O and wet‐milled MC/KCl. Lastly, the ball‐milling processes in different solutions led to various decreases of the crystallinity and the surface degradation due to carbonization and/or oxidization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44903.

Properties and Lithium Battery Applications of Solvate Ionic Liquid/CO2 Binary Mixtures

Introduction We have previously reported the intriguing physico-chemical properties of a series of solvate ionic liquids (SILs), which share many of the features of conventional ionic liquids, including high thermal stabilities, wide electrochemical windows and high ionic conductivities, making them attractive as electrolytes for future energy storage applications.1,2SILs may be exemplified by the 1:1 combination of Li[TFSA] and tetraglyme (G4), forming [Li(G4)][TFSA], shown in Fig.1. Recently, we extended our study of the properties of these SILs upon dilution with several molecular solvents.3 An important criterion4 of a SIL is the stability of the complex cation i.e. [Li(G4)]+. This can be conveniently determined by pulsed field gradient NMR (ratio of self-diffusion coefficients Dglyme/DLi is approximately unity), and furthermore by assessment of the residual (“free”) glyme in solution by Raman spectroscopy (deconvolution of the relevant modes gives typically <5% “free” glyme). Of particular note are the low polarity solvents such as toluene and HFE (1,1,2,2-tetrafluoroethyl,2,2,3,3-tetrafluoropropyl ether), which can effectively dilute the SILs, decreasing viscosity and increasing ionic conductivity, without disruption of the complex cation, [Li(G4)]+. Indeed, we have previously demonstrated the use of HFE in particular as a diluting solvent for a SIL applied to the lithium-sulfur battery.5Dilution of the SIL with HFE enables increased coulombic efficiency and rate capability, and also further reduces the solubility of the polysulfides. Moreover, as HFE is a non-flammable diluting solvent, the inherent safety advantage of the low-volatility SIL is not compromised. However, the use of a perfluorinated diluting solvent may be problematic environmentally. The formation of binary mixtures of ILs and high pressure carbon dioxide (CO2) has been studied extensively.6 As a low polarity solvent, it is reasonable to assume that CO2 would also not disrupt the complex cation structure of the SIL. Inspired by these analogous systems, we report here our findings for the dilution of a SIL with environmentally benign, high pressure CO2. Experimental Conductivity was measured by the complex impedance method with two platinum electrodes. The cell constant was determined by calibration with a dilute KCl solution, before transfer of the electrode assembly to the high pressure vessel. The determination of solubility of CO2 in the SIL was performed as described in detail elsewhere.7 Briefly, (i) the pressure change upon sorption of a known quantity of CO2 in the SIL, and (ii) the volume expansion of the SIL upon CO2sorption were determined, from which the solubility could be calculated. The Li deposition/dissolution and battery measurements were performed in a hand-made screw-plate cell that was assembled and then placed inside the high pressure vessel in an Ar-filled glovebox. Results and Discussion The large solubility of CO2 in the SIL promotes a dramatic enhancement in conductivity, as shown in Fig.2 below. This increase is conductivity is not unprecedented. Notable earlier reports in this area include that of Tominaga et al., who, after studying the effect of high pressure CO2 processing on polymer electrolytes, observed in situ a significant enhancement in conductivity for a series of solid polymer electrolytes, such as PMEO10LiTFSA (PMEO: poly-(oligo-oxyethylene glycol methacrylate)), under CO2 pressure.8 The reversible deposition and dissolution of lithium metal was studied in this SIL/CO2 binary mixture, as shown in Fig.3. The result obtained under Ar pressure is also shown for comparison. CO2, with high solubility, promotes efficient deposition and dissolution of Li. This can in part be attributed to higher conductivity (the use of high pressure Ar does not dramatically change the conductivity of the SIL). As shown in Fig.4, the binary SIL/CO2 mixture can also be applied to a typical Li-ion battery cathode such as LiCoO2(LCO), showing improved energy efficiency. In our presentation of this work, we will further discuss the solution properties of the SIL/CO2binary system, further electrochemical characterisation of the Li deposition/dissolution process, and comment on the application of this novel electrolyte for other conventional battery electrodes, including graphite. Acknowledgement This study was supported in part by the Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST).

Desorption kinetics of cesium from Fukushima soils

Understanding the behaviors of Cs+ in soils is crucial for evaluation of the impacts of disposal of soils contaminated by radiocesium, 137Cs. The desorption rate of Cs+ evaluated in relatively short periods of time may not be adequate for such a purpose. In this study, we investigated long-term desorption kinetics of 137Cs and 133Cs from soils collected in Fukushima Prefecture by batch desorption experiments in the presence of cation exchange resin as a sorbent. The sorbent can keep the concentration of Cs+ in the aqueous phase low and prevent re-sorption of desorbed Cs+. Up to 60% of 137Cs was desorbed after 139 d in dilute KCl media, which was larger than the desorption by conventional short-term extraction with 1 M ammonium acetate. Desorption of 137Cs continued even after this period. It was also found that high concentration of K+ prevented desorption of Cs+ in the initial stage of desorption, but the effect was alleviated with time. The desorbed fraction of stable Cs was smaller than that of 137Cs. This indicated that 137Cs may gradually move to more stable states in soils. The half-life of 137Cs desorption from the slowest sorption site was estimated to be at least two years by a three-site desorption model.

A Comprehensive Study of Extraction of L-Lysine with Sec-Octylphenoxy Acetic Acid in Sulfonated Kerosene

Extraction of L-lysine with sec-octylphenoxy acetic acid (CA-12) in sulfonated kerosene was investigated under different pH and CA-12 concentrations, and optimized conditions were determined. Half-saturation fluorometric analysis and atomic force microscopy showed that the electrovalent bond between L-lysine and CA-12 acted as the main force to partition L-lysine into organic phase. Moreover, the mathematically analyzed extraction process indicated that the extractive complex was a 1:2 L-lysine • CA-12 structure. The initial extraction efficiency could reach 78.9 ± 1.2% and the total strip extraction efficiency after three strip extractions could reach 95.7 ± 1.8% by using a dilute KCl solution.

Traceable mean activity coefficients and osmotic coefficients in aqueous magnesium chloride solutions at T = 298.15 K up to a molality of 3.0 mol · kg−1

The Hückel equation used in this study for the thermodynamic activity quantities in dilute MgCl2 solutions up to an ionic strength (=Im) of 1.5mol·kg−1 contains two parameters being dependent on the electrolyte, i.e., those of B and b1. The former is linearly related to the ion-size parameter in the Debye–Hückel equation and the latter is the coefficient of the linear correction term with respect to the molality. For more concentrated solutions up to Im of 9.0mol·kg−1, an extended Hückel equation was used. For it, the Hückel equation was extended with a quadratic term in molality, and the coefficient of this term is the third parameter b2. Parameters B and b1 for dilute MgCl2 solutions were obtained from the isopiestic data of Robinson and Stokes for solutions of this salt and KCl [Trans. Faraday Soc. 36 (1940) 733] by using the previous Hückel parameters for dilute KCl solutions [J. Chem. Eng. Data 54 (2009) 208]. The resulting parameters for MgCl2 solutions were successfully tested with all isopiestic data available in the literature for dilute solutions of this salt. For less dilute solutions, new values for parameters b1 and b2 were determined for the extended version of the Hückel equation of MgCl2 solutions from the isopiestic data of Rard and Miller [J. Chem. Eng. Data 26 (1981) 38] for NaCl and MgCl2 solutions but the dilute-solution value for parameter B was used. The previous extended Hückel equation for concentrated NaCl solutions was used in this estimation (see the KCl citation above). In the tests of the new parameter values for these less dilute solutions, the existing vapor pressure and isopiestic data were used, and these data support well the new parameters. Reliable thermodynamic activity quantities for MgCl2 solutions can, therefore, be obtained using the new Hückel and extended Hückel equations. The activity coefficients, osmotic coefficients, and vapor pressures obtained with these equations are tabulated here at rounded molalities. These values were compared to those reported in the several previous important tabulations.

Conductivity and electrophoretic mobility of dilute ionic solutions

Two complementary continuum theories of electrokinetic transport are examined with particular emphasis on the equivalent conductance of binary electrolytes. The "small ion" model [R.M. Fuoss, L. Onsager, J. Phys. Chem. 61 (1957) 668] and "large ion" model [R.W. O'Brien, L.R. White, J. Chem. Soc. Faraday Trans. 2 (74) (1978) 1607] are both discussed and the "large ion" model is generalized to include an ion exclusion distance and to account in a simple but approximate way for the Brownian motion of all ions present. In addition, the "large ion" model is modified to treat "slip" hydrodynamic boundary conditions in addition to the standard "stick" boundary condition. Both models are applied to the equivalent conductance of dilute KCl, MgCl(2), and LaCl(3) solutions and both are able to reproduce experimental conductances to within an accuracy of several tenths of a percent. Despite fundamental differences in the "small ion" and "large ion" theories, they both work equally well in this application. In addition, both "stick-large ion" and "slip-large ion" models are equally capable of accounting for the equivalent conductances of the three electrolyte solutions.

Ion-Rejection, Electrokinetic and Electrochemical Properties of a Nanoporous Track-Etched Membrane and Their Interpretation by Means of Space Charge Model

Due to their straight cylindrical pores, nanoporous track-etched membranes are suitable materials for studies of the fundamentals of nanofluidics. In contrast to single nanochannels, the nano/micro interface, in this case, can be quantitatively considered within the scope of macroscopically 1D models. The pressure-induced changes in the concentration of dilute KCl solutions (salt rejection phenomenon) have been studied experimentally with a commercially available nanoporous track-etched membrane of poly (ethylene terephthalate) (pore diameter ca. 21 nm). Besides that, we have also studied the concomitant stationary transmembrane electrical phenomenon (filtration potential) and carried out time-resolved measurements of the electrical response to a rapid pressure switch-off (within 5-10 ms). The latter has enabled us to split the filtration potential into the streaming potential and membrane potential components. In this way, we could also confirm that the observed nonlinearity of filtration potential, as a function of the transmembrane volume flow, was primarily caused by the salt rejection. The results of experimental measurements have been interpreted by means of a space charge model with the surface charge density being a single fitting parameter (the pore size was estimated from the membrane hydraulic permeability). By using the surface charge density fitted to the salt rejection data, the results of electrical measurements could be reproduced theoretically with a typical accuracy of 10% or better. Taking into account the simplifications made in the modeling, this accuracy appears to be good and confirms the quantitative applicability of the basic concept of space charge model to the description of transport properties of dilute electrolyte solutions in nanochannels of ca. 20 nm.

Re-Evaluation of the Thermodynamic Activity Quantities in Aqueous Lithium Chloride Solutions at 25 °C up to a Molality of 6.0 mol·kg−1

The Hückel equation used in this study to correlate the experimental activities of dilute LiCl solutions up to a molality of about 1.0 mol·kg−1 contains two parameters being dependent on the electrolyte: B [that is related closely to the ion-size parameter (a*) in the Debye−Hückel equation] and b1 (this parameter is the coefficient of the linear term with respect to the molality, and this coefficient is related to hydration numbers of the ions of the electrolyte). In more concentrated solutions up to a molality of 6.0 mol·kg−1, an extended Hückel equation was used. It contains additionally a quadratic term with respect to the molality, and the coefficient of this term is the parameter b2. The values of parameters B and b1 for dilute LiCl solutions were determined from the isopiestic data measured by Robinson and Sinclair for KCl and LiCl solutions (J. Am. Chem. Soc. 1934, 56, 1830−1835) by using the Hückel parameters determined recently by Partanen and Covington for dilute KCl solutions (J. Chem. Eng. Data 2009, 54, published ASAP July 24, 2008). The resulting parameter values were tested with the sparse cell potential and isopiestic data existing in the literature for dilute LiCl solutions. In more concentrated solutions, new values of parameters b1 and b2 were determined for the extended Hückel equation of LiCl but the same value of parameter B was used as for dilute solutions. The values of b1 and b2 for LiCl were determined from the isopiestic data measured by Robinson for NaCl and LiCl solutions (Trans. Faraday Soc. 1945, 41, 756−758) by using the extended Hückel equation determined recently by us for concentrated NaCl solutions (see the citation above). The resulting extended Hückel equation was tested with all reliable experimental data presented in the literature on the basis of electrochemical, isopiestic, and direct vapor pressure measurements. Most of these data can be reproduced within experimental error by means of the extended Hückel equation up to a molality of 6.0 mol·kg−1. Reliable activity and osmotic coefficients for LiCl solutions can, therefore, be calculated by using the new Hückel equations, and they have been tabulated here at rounded molalities. The activity quantities obtained from these equations were compared to the values suggested by Robinson and Stokes (Trans. Faraday Soc. 1949, 45, 612−624), to those calculated by using the Pitzer equations of Pitzer and Mayorga (J. Phys. Chem. 1973, 77, 2300−2308), of Kim and Frederick (J. Chem. Eng. Data 1988, 33, 177−184), and of Marshall et al. (J. Chem. Eng. Data 1995, 40, 1041−1052), and to those calculated by using the extended Hückel equation of Hamer and Wu (J. Phys. Chem. Ref. Data 1972, 1, 1047−1099).

Direct measurement of particle–bubble interaction forces using atomic force microscopy

Interaction forces between a hydrophilic silica particle and an air bubble were measured by atomic force microscopy using simplified model systems with deionized water and dilute KCl solutions. Contributions from the hydrodynamic force were minimized by using a low piezo speed. Particle–bubble separation distance and the bubble spring constant were calculated from linear regression of the piezo extension versus cantilever deflection. The bubble surface potential was then estimated from fitting the AFM-measured forces to the Hogg–Healy–Fuerstenau (HHF) model, using the surface element integration (SEI) method. Surface potentials obtained for the bubble at a low applied force were comparable with the literature data, suggesting that the simplified model used here can give a reasonable estimation of the bubble surface potential under moderate applied forces. Interaction forces between a silica particle and an air bubble were also measured at different locations on the air bubble surface. The force curves obtained at the edges of the bubble fitted very well to the theoretical force curves regardless of the applied force, while curves obtained at the center and halfway to the center, were more difficult to fit, in particular at higher applied forces (> 13 nN), suggesting that force curves obtained at the edges of the air bubble might be less prone to deformation effects.

Re-Evaluation of the Thermodynamic Activity Quantities in Aqueous Sodium and Potassium Chloride Solutions at 25 °C

The Huckel equation is used to correlate the experimental activities of dilute NaCl and KCl solutions up to a molality of about 1.0 mol·kg−1. The two parameters of this equation are dependent on the electrolyte and are B [which is simply related to the ion-size parameter (a*) in the Debye−Huckel equation] and b1 (which is the coefficient of the linear term in molality and related to hydration numbers of the ions of the electrolyte). In more concentrated solutions up the saturation for both electrolytes, an extended Huckel equation was used, and it contains, additionally, a quadratic term with respect to the molality with parameter b2. The values of parameters B and b1 for dilute KCl solutions were determined from the cell potential differences measured by Hornibrook et al. on concentration cells with transference (J. Am. Chem. Soc. 1942, 64, 513−516). With these values of KCl, the corresponding parameter values for NaCl solutions were determined from the isopiestic data of Robinson for NaCl and KCl soluti...

Structure and dehydration of layered perovskite niobate with bilayer hydrates prepared by exfoliation/self-assembly process

The crystals of an H-form niobate of HCa 2Nb 3O 10· xH 2O ( x=0.5) being tetragonal symmetry (space group P4/ mbm) with unit cell parameters a=5.4521(6) and c=14.414(2) Å were exfoliated into nanosheets with the triple-layered perovskite structure. The colloid suspension of the nanosheets was put into dialysis membrane tubing and allowed self-assembly in a dilute KCl solution. By this method, a novel layered K-form niobate KCa 2Nb 3O 10· xH 2O ( x=1.3, typically) with bilayer hydrates in the interlayer was produced. The Rieveld refinement and transmission electron microscope (TEM)/selected-area electron diffraction (SAED) observation indicated that the orientations of the a-/ b-axis of each nanosheet as well as the c-axis are uniform, and the self-assembled compound had the same symmetry, tetragonal ( P4/ mbm) with a=5.453(2) and c=16.876(5) Å, as the H-form precursor; the exfoliation/self-assembly process does not markedly affect the two-dimensional lattice of the layer. The large basal spacing resulted from the interlayer K + ions solvated by two layers of water molecules. The interlayer bilayers-water was gradually changed to monolayer when the temperatures higher than 100 °C, and all the water molecules lost when over 600 °C. Accompanying the dehydration, the crystal structure transformed from tetragonal to orthorhombic symmetry. Water molecules may take an important role for the layer layered compound to adjust the unit cell to tetragonal symmetry.

Influence and Interference by Thymol added as a Biocide on the Analysis of Precipitation Samples

Thymol (2-isopropyl-5-methyl phenol) is recommended for the preservation of precipitation samples to suppress the microbial activity and conversion of organic acids unless refrigeration can be used. However, the addition of thymol to precipitation samples influences and interferes with the analysis of samples. The pH value of dilute (10-4M) KCl solution decreased when the amount of thymol added was more than 100 mg/100 ml dilute KCl solution. In contrast, the pH value increased when the amount of thymol added was less than 10 mg /100 ml precipitation sample. The absorbance in the colorimetric method (indophenol blue method for NH4+analysis) was decreased by the addition of thymol. This result was probably caused by the competitive reaction of thymol and phenol through their similar chemical structures. The decrease in the absorbance was dependent on the amount of thymol added. Therefore, the indophenol blue method cannot be recommended for samples to which thymol is added before starting collection because it is impossible to add an appropriate amount of thymol.

ζ potential measurement of volcanic rocks from Aso caldera

We deduced the ζ potential of various rocks in Aso caldera from streaming potential measurements in laboratory. In contrast to the conventional observation that the ζ potential of crustal rocks is mostly negative under typical geologic conditions, almost half of the samples equilibrated with dilute KCl solution show positive values of ζ potential at pH 4.5–5.5. The samples showing positive ζ are characterized by relatively low SiO2 content and abundance of elements having high isoelectric points, and found to be localized around the summit of Mt. Takadake where the positive correlation between self‐potential (SP) and altitude is observed. We emphasize that measurements of ζ potential of volcanic rocks are very important to give more appropriate interpretations of SP data from volcanic fields.

Direct evidence for fixed ionic groups in the hydrogel of an electrolyte diode

Current–voltage characteristics of polyvinyl alcohol (PVA)–glutardialdehyde hydrogel cylinders were measured in dilute KCl solutions. The gel was the same type which had been applied in previous electrolyte diode experiments. Below 10−2 molar KCl concentration the measured characteristics were nonlinear and at higher voltages the current was unstable. These results were explained by concentration polarization phenomena due to fixed negative charges present in the hydrogel and by electroconvection in the anodic boundary layer of the gel cylinder where a strong electric field can appear. To confirm these hypotheses further experiments were performed where spatially resolved concentration polarization data could be obtained inside the gel and in its close neighbourhood. The proposed model was also supported with semi-quantitative simulations which were able to reproduce the measured nonlinear characteristics and the observed concentration polarization phenomena. The fixed negative charges are most probably ionized carboxylic acid groups contaminating the PVA and the PVA-based hydrogel.