Excess Hydroxide Research Articles

A Synopsis on CO2 Capture by Synthetic Hydrogen Bonding Receptors.

Carbon dioxide (CO2) is one of the most abundant greenhouse gases in Earth's atmosphere and responsible for global warming. Therefore, aerial CO2 capture and sequestration has become a major task for human community. Though several adsorbents for CO2 including activated carbon, zeolites, metal-organic frameworks (MOFs), and other surface-modified porous materials are well developed, the supramolecular approaches using synthetic hydrogen-bonding receptors are less explored. This review article highlights the synthetic development of various artificial receptors and their properties toward fixation of aerial CO2 as carbonate (CO3 2-), bicarbonate (HCO3 -), or carbamate (-NHCOO-/>NCOO-) ions, induced by excess fluoride (F-) or hydroxide (OH-) ions as their tetrabutylammonium salts. The utilization of encapsulated carbonate/bicarbonate/carbamate complexes in anion exchange metathesis for separation of oxyanions from aqueous solutions are also discussed. In addition, the release of CO2 and regeneration of receptor molecules are described in a number of occasions. Most importantly, the formation of anion complexes as crystalline materials in solid-state is described in terms of supramolecular chemistry and correlated with their solution-state properties. Finally, the types of receptors containing various functional groups are scrutinized in CO2 uptake, storage, and release processes and hints of endeavours for future research are delineated.

Structure-property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives.

Presented here is the design, synthesis, and study of a variety of novel hydrogen-bonding-capable π-conjugated N-heteroacenes, 1,4-dihydropyrazino[2,3-b]quinoxaline-2,3-diones (DPQDs). The DPQDs were accessed from the corresponding weakly hydrogen-bonding dicyanopyrazinoquinoxaline (DCPQ) suspensions with excess potassium hydroxide, resulting in moderate to good yields. Both families of compounds were analyzed by UV-vis and NMR spectroscopy, where the consequences of hydrogen bonding capability could be assessed through the structure-property studies. Conversion of the DCPQs into hydrogen-bonding capable DPQDs results in modulation of frontier MO energies, higher molar extinction coefficients, enhanced crystallinity, and on-average higher thermal stability (where in some cases the 5% weight loss temperature is increased by up to 100 °C). Single crystal X-ray diffraction data could be obtained for three DPQDs. One reveals pairwise hydrogen bonding in the solid state as well as a herringbone packing arrangement rendering it a promising candidate for additional studies in the context of organic optoelectronic devices.

A CoII-Hydroxide Complex That Converts Directly to a CoII-Acetamide during Catalytic Nitrile Hydration.

In exploring structural and functional mimics of nitrile hydratases, we report the synthesis of the pseudo-trigonal bipyramidal CoII complexes (K)[CoII(DMF)(LPh)] (1(DMF)), (NMe4)2[CoII(OAc)(LPh)] (1(OAc)), and (NMe4)2[CoII(OH)(LPh)] (1(OH)) (LPh = 2,2',2''-nitrilo-tris-(N-phenylacetamide; DMF = N,N-dimethylformamide; -OAc = acetate)). The complexes were characterized using NMR, FT-IR, ESI-MS, electronic absorption spectroscopy, and X-ray crystallography, showing the LPh ligand to bind in a tetradentate tripodal fashion alongside the respective ancillary donor. One of the complexes, 1(OH), is an unusual structural and functional mimic of the Co active site in Co nitrile hydratases. 1(OH) reacted with acetonitrile to yield the CoII-acetamide complex (NMe4)2[CoII(NHC(O)CH3)(LPh)], 2, which was also thoroughly characterized. In the presence of excess hydroxide, 1(OH) was found to catalyze quantitative conversion of the added hydroxide into acetamide. Despite the differences in Co oxidation state in nitrile hydratases and 1(OH) (CoIII versus CoII, respectively), 1(OH) was nonetheless an effective nitrile hydration catalyst, selectively producing acetamide over multiple turnovers.

Chemiluminescence initiated by nebulization of oxidant- and catalyst-free aqueous luminol solutions

Chemiluminescence (CL), i.e., the emission of light during chemical reactions without external optical excitation, is widely used in clinical medicine, bioassays, reporter gene assays, and bioimaging. Given the complexity of traditional CL systems, which typically contain catalysts and oxidants, one-component (i.e., luminophore-only) alternatives are urgently required. Herein, to demonstrate the feasibility of such simple systems, we realize CL by nebulizing oxidant- and catalyst-free aqueous luminol solutions and demonstrate that it originates from the oxidation of luminol by the •OH radicals spontaneously formed on the microdroplet surface. The higher intensity of this CL system compared to that observed for a reference bulk-phase CL system containing H2O2 as an oxidant and FeSO4 as a catalyst is ascribed to the high specific surface area and luminol adsorption capacity of the microdroplets, and excess hydroxide ions on their surface. Thus, this work demonstrates that microdroplets provide a favorable environment for CL reactions and paves the way for the establishment of one-component CL systems.

Developing machine-learned potentials to simultaneously capture the dynamics of excess protons and hydroxide ions in classical and path integral simulations.

The transport of excess protons and hydroxide ions in water underlies numerous important chemical and biological processes. Accurately simulating the associated transport mechanisms ideally requires utilizing abinitio molecular dynamics simulations to model the bond breaking and formation involved in proton transfer and path-integral simulations to model the nuclear quantum effects relevant to light hydrogen atoms. These requirements result in a prohibitive computational cost, especially at the time and length scales needed to converge proton transport properties. Here, we present machine-learned potentials (MLPs) that can model both excess protons and hydroxide ions at the generalized gradient approximation and hybrid density functional theory levels of accuracy and use them to perform multiple nanoseconds of both classical and path-integral proton defect simulations at a fraction of the cost of the corresponding abinitio simulations. We show that the MLPs are able to reproduce abinitio trends and converge properties such as the diffusion coefficients of both excess protons and hydroxide ions. We use our multi-nanosecond simulations, which allow us to monitor large numbers of proton transfer events, to analyze the role of hypercoordination in the transport mechanism of the hydroxide ion and provide further evidence for the asymmetry in diffusion between excess protons and hydroxide ions.

On the Propensity of Excess Hydroxide Ions at the Alcohol Monolayer–Water Interface

Atomistic molecular dynamics simulations have been employed to study the self-ion (H+ and OH-) distribution at the interface between long-chain C16-OH alcohol (cetyl alcohol) monolayer and water. It is well known that the free air-water interface is acidic due to accumulation of the hydronium (H3O+) ions at the interface. In the present study, we have observed that contrary to the air-water interface, at the long-chain alcohol monolayer-water interface, it is the hydroxide (OH-) ion, not the hydronium ion (H3O+) that gets accumulated. By calculating the potential of mean forces, it is confirmed that there is extra stabilization for the OH- ions at the interface relative to the bulk, but no such stabilization is observed for the H3O+ ions. By analyzing the interaction of the self-ions with other constituents in the medium, it is clearly shown that the favorable interaction of the OH- ions with the alcoholic -OH groups stabilizes this ion at the interface. By calculating coordination numbers of the self-ions it is observed that around 50% water neighbors are substituted by alcoholic -OH in case of the hydroxide ion at the interface, whereas in the case of hydronium ions, only 15% water neighbors are substituted by the alcoholic -OH. The most interesting observation about the local structure and H-bonding pattern is that the hydroxide ion acts solely as the H-bond acceptor, but the hydronium ion acts only as the H-bond donor.

Insight into the role of excess hydroxide ions in silicate condensation reactions.

The formation of silicate oligomers in the early stages is key to zeolite synthesis. The pH and the presence of hydroxide ions are important in regulating the reaction rate and the dominant species in solutions. This paper describes the formation of silicate species, from dimers to 4-membered rings, using ab initio molecular dynamics simulations in explicit water molecules with an excess hydroxide ion. The thermodynamic integration method was used to calculate the free energy profile of the condensation reactions. The hydroxide group's role is not only to control the pH of the environment, but also to actively participate in the condensation reaction. The results show that the most favorable reactions are linear-tetramer and 4-membered-ring formation, with overall barriers of 71 kJ mol-1 and 73 kJ mol-1, respectively. The formation of trimeric silicate, with the largest free-energy barrier of 102 kJ mol-1, is the rate-limiting step under these conditions. The excess hydroxide ion aids in the stabilization of the 4-membered-ring structure over the 3-membered-ring structure. Due to a relatively high free-energy barrier, the 4-membered ring is the most difficult of the small silicate structures to dissolve in the backward reaction. This study is consistent with the experimental observation that silicate growth in zeolite synthesis is slower in a very-high-pH environment.

TELP theory: Elucidating the major observations of Rieger et al. 2021 in mitochondria

The transmembrane-electrostatically localized protons (TELP) theory may represent a complementary development to Mitchell's chemiosmotic theory. The combination of the two together can now excellently explain the energetics in mitochondria. My calculated transmembrane-attractive force between an excess proton and an excess hydroxide explains how TELP may stay within a 1-nm thin layer at the liquid-membrane interface. Consequently, any pH sensor (sEcGFP) located at least 2–3 nm away from the membrane surface will not be able to see TELP. This feature as predicted from the TELP model was observed exactly in the experiment of Rieger et al., 2021. In contrast to their belief “the Δp at ATP synthase is almost negligible under OXPHOS conditions”, I find, when TELP activity is included in the energy calculations, there is plenty of total protonic Gibbs free energy (ΔGT) well above the physiologically required value of −24.5 kJ mol−1 to drive ATP synthesis through FoF1-ATP synthase.

ZnS/Cd1-xZnxS composite photocatalyst synthesized with excessive strong alkali solution as a hydrothermal solvent: The chemical equilibrium theory of the synthesis process and its influence on photocatalytic performance

The ZnS/Cd1-xZnxS composite photocatalyst was successfully synthesized using a hydrothermal solvent by adding excess hydroxide ions. The ZnS/Cd1-xZnxS composite photocatalyst showed excellent photocatalytic activity for hydrogen production with a hydrogen evolution rate of 21.8 mmol/g−1 h−1, which is the highest photocatalytic activity reported to date among visible-light-driven photocatalysts without loading cocatalysts. According to the theoretical calculation and analysis of the chemical equilibrium in the synthesis process, the synthesized Cd1-xZnxS solid solution contained a certain amount of ZnS. A certain amount of ZnS was also contained in the synthesized Cd1-xZnxS solid solution based on experimental results, thus demonstrating the validity of the theoretical calculation. Experimental results showed that the key factor affecting the photocatalytic activity of hydrogen production for the ZnS/Cd1-xZnxS composite photocatalyst was not the heterojunction formed between ZnS and Cd1-xZnxS but rather the stacking fault structures in the Cd1-xZnxS solid solution. However, more stacking fault structures could be formed in the Cd1-xZnxS solid solution due to the presence of ZnS.

Cerium Compounds Coating as a Single Self-Healing Layer for Corrosion Inhibition on Aluminum 3003

The formation of cerium hydroxide was studied, and its capacity as a corrosion inhibitor on aluminum substrates was evaluated. These particles were deposited by immersing the substrate in a bath with cerium nitrate and hydrogen peroxide. Four different immersion times were used to determine the differences in behavior from low concentrations to an excess of particles on the surface. The coatings were analyzed morphologically by scanning electron microscope (SEM) and optical microscope, and chemically by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Electrochemical corrosion analysis was studied using cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and electrochemical noise (EN). The results show that for 2 and 5 min of immersion, there was corrosion inhibition caused by the presence of cerium Ce3+ in the coating, but with excess cerium hydroxide particles, corrosion was favored. The presence of cerium particles favors corrosion at 30 s of immersion. This is the same case at 60 min, where corrosion was favored by the excess of Ce4+ particles on the surface.

Ferrous-Oxalate-Modified Aramid Nanofibers Heterogeneous Fenton Catalyst for Methylene Blue Degradation

The heterogeneous Fenton system has drawn great attention in recent years due to its effective degradation of polluted water capability without limitation of the pH range and avoiding excess ferric hydroxide sludge. Therefore, simple chemical precipitation and vacuum filtration method for manufacturing the heterogeneous Fenton aramid nanofibers (ANFs)/ferrous oxalate (FeC2O4) composite membrane catalysts with excellent degradation of methylene blue (MB) is reported in the study. The morphology and structure of materials synthesized were characterized by scanning electron microscope (SEM), X-ray energy spectrum analysis (EDS), infrared spectrometer (FTIR), and X-ray diffraction (XRD) equipment. The 10 ppm MB degradation efficiency of composite catalyst and ferrous oxalate (FeC2O4) within 15 min were 94.5% and 91.6%, respectively. The content of methylene blue was measured by a UV-Vis spectrophotometer. Moreover, the dye degradation efficiency still could achieve 92% after five cycles, indicating the composite catalyst with excellent chemical stability and reusability. Simultaneously, the composite catalyst membrane can degrade not only MB but also rhodamine B (RB), orange II (O II), and methyl orange (MO). This study represents a new avenue for the fabrication of heterogeneous Fenton catalysts and will contribute to dye wastewater purification, especially in the degradation of methylene blue.

Accurate diffusion coefficients of the excess proton and hydroxide in water via extensive ab initio simulations with different schemes.

Despite its simple molecular formula, obtaining an accurate in silico description of water is far from straightforward. Many of its very peculiar properties are quite elusive, and in particular, obtaining good estimations of the diffusion coefficients of the solvated proton and hydroxide at a reasonable computational cost has been an unsolved challenge until now. Here, I present extensive results of several unusually long ab initio molecular dynamics (MD) simulations employing different combinations of the Born-Oppenheimer and second-generation Car-Parrinello MD propagation methods with different ensembles (NVE and NVT) and thermostats, which show that these methods together with the RPBE-D3 functional provide a very accurate estimation of the diffusion coefficients of the solvated H3O+ and OH- ions, together with an extremely accurate description of several properties of neutral water (such as the structure of the liquid and its diffusion and shear viscosity coefficients). In addition, I show that the estimations of DH3O+ and DOH- depend dramatically on the simulation length, being necessary to reach timescales in the order of hundreds of picoseconds to obtain reliable results.

RILEM TC 258-AAA Round Robin Test: Alkali release from aggregates and petrographic analysis. Critical review of the test method AAR-8

To create an international recommendation concerning the release of alkalis, test method AAR-8 was developed within the scope of RILEM TC 258-AAA activities. The first round robin test was performed using five aggregate types, and further investigation was conducted as RRT2, leading to the final version of the AAR-8 recommendation. Five aggregates with different mineralogies and origins were immersed in specific volumes of NaOH or KOH solutions with excess calcium hydroxide maintained 38 °C and 60 °C respectively. Samples of the immersion test solution were removed at intervals of 2, 6, 13, 26, and 52 weeks by pipetting and chemically analyzed for NaOH or KOH test solutions. The amount of alkali released was expressed in grams of Na2O, K2O, and Na2Oe per kilogram of the respective aggregate. The results obtained are presented. Based on the data, several changes to the original version of the test method are proposed.

Inhibition of Hydrogen Evolution by a Bifunctional Membrane between Anode and Electrolyte of Aluminum-Air Battery.

The hydrogen evolution reaction of the anode is a severe barrier that limits the further commercial application of Al–air batteries. Therefore, this study introduces a bifunctional membrane for the inhibition of hydrogen evolution in Al–air batteries. The reference to Al2O3@PAN as “bifunctional” means that it has both hydrophobic and anti-corrosion functions. Al2O3 can effectively inhibit the migration of hydroxide ions, and PAN is an excellent hydrophobic material. The bifunctional membrane is placed between the aluminum anode and the electrolyte, which can prevent the invasion of excess water and hydroxide ions, thereby inhibiting the hydrogen evolution corrosion of the anode. Electrochemical tests have confirmed that the corrosion inhibition rate of a bifunctional membrane containing 1.82 wt. % Al2O3@PAN is as high as 89.24%. The specific capacity of Al–air batteries containing this membrane can reach 1950 mAh/g, and the utilization rate of the aluminum anode has reached 61.2%, which is helpful in reducing the waste of aluminum resources. The results prove that the bifunctional membrane has excellent anti-corrosion properties. Bifunctional membranes can also be used to prevent the corrosion of metals in other fields.

Recommendation of RILEM TC 258-AAA: RILEM AAR-8: determination of potential releasable alkalis by aggregates in concrete

The test method AAR-8 is intended to be used for assessing the potential amount of alkalis released by aggregates in field concrete in the long-term. This is done by measuring the amounts of sodium and potassium ions released from the fine graded (< 4 mm) aggregate immersed in (0.7 M) KOH and NaOH solutions, respectively, at elevated temperature when in contact with excess calcium hydroxide. It is of great importance to realise that this accelerated test method must be considered as a mere indication of potential (maximum) alkali release by the aggregates, rather than a quantification used for the alkali inventory calculations.

Green Synthesis of Iron-Doped Cobalt Oxide Nanoparticles from Palm Kernel Oil via Co-Precipitation and Structural Characterization.

In this study, a bio-derived precipitating agent/ligand, palm kernel oil, has been used as an alternative route for the green synthesis of nanoparticles of Fe-doped Co3O4 via the co-precipitation reaction. The palm oil was extracted from dried palm kernel seeds by crushing, squeezing and filtration. The reaction of the palm kernel oil with potassium hydroxide, under reflux, yielded a solution containing a mixture of potassium carboxylate and excess hydroxide ions, irrespective of the length of saponification. The as-obtained solution reacts with an aqueous solution containing iron and cobalt ions to yield the desired metallo-organic precursor, iron cobalt carboxylate. Characterization of the precursors by IR and gas chromatography (GC) attests to the presence of carboxylate fatty acids in good agreement with the proportion contained in the oil, and ICP confirms that the metallic ratios are in the proportion used during the synthesis. Analysis of the products thermally decomposed between 400 °C and 600 °C by XRD, EDX, TEM and ToF-SIMS, established that cobalt iron oxide nanoparticles (Co(1−x)Fex)3O4 were obtained for x ≤ 0.2 and a nanocomposite material (Co(1−x)Fex)3O4/Fe3O4 for x ≥ 0.2, with sizes between 22 and 9 nm. ToF-SIMS and XRD provided direct evidence of the progressive substitution of cobalt by iron in the Co3O4 crystal structure for x ≤ 0.2.

(Invited) Electrochemical Separation of Carbon Dioxide Using Anion Exchange Membranes

Anion exchange membranes provide a useful platform for electrochemical separation of carbon dioxide from dilute gas streams. Electrochemically-driven acid gas separations require a cathode reaction that generates hydroxide and an anode reaction that consumes hydroxide. Hydroxide generated at the cathode reacts with CO2 to make carbonate, which is transported across the membrane to the anode. The reverse process at the anode drives release of CO2. The reactions must be compatible with the gas mixtures present and must function over a pH range of about 7-12 for anode and 12-14 for cathode. These requirements allow flexibility for a range of electrode reactions. Four cells can be made from the reactions of hydrogen, oxygen, and water: the fuel cell1, electrolyzer, hydrogen pump, and oxygen pump2. Additionally, certain battery electrodes, such as nickel hydroxide / oxyhydroxide can be used to eliminate the gaseous reactants or byproducts.We will present experimental and model results for electrochemical separators using various electrode reactions. Applications include direct air capture of CO2 and scrubbing of air to >99% CO2 removal for use in hydroxide exchange membrane fuel cells. To date, the best studied system is the separator using fuel cell chemistry in a scrubbing application. Recent progress is shown in Figure 1. In the past three years, an order of magnitude improvement in air scrubbing capacity has been achieved through careful optimization of mass transport.Electrochemical separation of CO2 is well described by standard electrochemical models and much insight can be gained into the methods to improve performance. The role of membrane resistance provides a clear example. A pH gradient must be maintained between anode and cathode, both to create the thermodynamic driving force to transport CO2 from low partial pressure to high and to increase the kinetics of CO2 capture by providing excess hydroxide at cathode. Anion diffusion tends to reduce this pH gradient, while migration strengthens the gradient. As a result, the CO2 capture rate at constant current density tends to increase with increasing membrane resistance1, and the best fuel cell membranes have too high of conductivity to make optimized electrochemical separators. Figure 2 shows an experimental validation of the effect of membrane resistance. CO2 separation is greatly improved as membrane resistance increases, both in the case of intentionally degraded membranes and fresh membranes of reduced conductivity. The performance difference is greatest at the lowest current density, where the potential gradient across the membrane is smallest. References Matz, S. et al. Demonstration of Electrochemically-Driven CO 2 Separation Using Hydroxide Exchange Membranes . J. Electrochem. Soc. 168, 014501 (2021).Rigdon, W. A. et al. Carbonate Dynamics and Opportunities With Low Temperature, Anion Exchange Membrane-Based Electrochemical Carbon Dioxide Separators. J. Electrochem. Energy Convers. Storage 14, 020701 (2017). Figure 1: Progression of electrochemical carbon dioxide separation performance from 2018-2020 using 25 cm2 single cells with fuel cell chemistry. Air with 400 ppm CO2 was fed to the cathode. Cell temperature & relative humidity: 70 °C, 80% (2018-1, 2018-2) or 60 °C, 70% (2019-1, 2019-2, 2020); current density: 20 mA/cm2 (2018-1, 2018-2, 2019-1, 2019-2) or 35 mA/cm2 (2020); outlet pressure: 100 kPaa (2018-1, 2018-2, 2019-1), 175 kPaa (2019-2), or 250 kPaa (2020). Anode hydrogen flow rate was 50 sccm (2018-1, 2018-2), 7 sccm (2019-1, 2019-2), or 12 sccm (2020). EDCS:FC ratio is the active area of electrochemical separator divided by the active area of the fuel cell that it could supply based on the air flow rate, assuming 1.5 A/cm2 fuel cell current density and 1.5x cathode stoichiometry. Figure 2: Effect of membrane area-specific resistance on CO2 separation performance. Conditions: 60 °C cell temperature, 90% relative humidity, 20 sccm H2 flow at anode, 1000 sccm air (w/ 400 ppm CO2) at cathode, atmospheric pressure. Membrane details: A) PAP-TP-85 membrane B) Same as A, but slightly degraded to increase resistance (140 h dry exposure in 80 °C oven). C) Same as A, but moderately degraded to increase resistance (96 h dry exposure in 97 °C oven). D) Fumasep FAA-HM membrane from FuMA-Tech Gmbh. Figure 1

Diradicals or Zwitterions: The Chemical States of m -Benzoquinone and Structural Variation after Storage of Li Ions

Diradicals or Zwitterions: The Chemical States of <i>m</i> -Benzoquinone and Structural Variation after Storage of Li Ions

Novel Multifunctional Janus‐Type Membrane on Al Anode for Corrosion Protection

AbstractNovel multifunctional Janus‐type membrane with both hydrophobic and anticorrosion abilities is constructed on the surface of aluminum (Al), using MoS2 as a hydrophobic layer and ZnO as a corrosion‐resistant layer. Al anode coated with the Janus‐type membrane is used as an example to study the specific property of the as‐prepared Janus‐type membrane. In the Al–air battery, the self‐corrosion of the Al anode is well inhibited since the Janus‐type membrane can block the invasion of excess hydroxide ions and water molecules simultaneously. The results show that the inhibition efficiency of the Janus‐type membrane is as high as 79.2%. Furthermore, the electrochemical measurements demonstrate that the discharge specific capacity of the Al–air battery with the Janus‐type membrane can reach up to 2095 mAh g−1, approximately two times as much as that of traditional batteries. The integrated strategy of combining hydrophobic and anticorrosion membrane is a novel method for corrosion protection of metal electrode. This Janus‐type membrane holds a great potential toward corrosion inhibition for the other metal in alkaline environment as well.

A molecular dynamics study on the interfacial properties of millerite

The present study aims at developing force field parameters for describing the millerite structure and subsequently for investigation of its interfacial properties under varying conditions within the framework of molecular dynamics simulations. The first set of calculations were performed to obtain the required force field parameters, validated through reproduction of the bulk properties. This was followed by estimation of the surface energy and evaluation of the collector physisorption onto the non-polar (100) and (110) surfaces. Collector molecules exhibited higher affinity towards the former, with the branched alkyl chain favoring the interactions with either of the surfaces. Further simulations were conducted to examine the changes in the contact angle of the intrinsically hydrophilic (110) surface upon oxidization. Observations through transition from the neutral surface fully covered by elemental sulfur to a charge-bearing surface containing sulfur and polysulfides were compared against the theoretical predictions made by the Lippmann equation, and the discrepancies were attributed to the significance of line tension at the atomic scale. Finally, propensity of collector molecules towards the positively and negatively charged (110) surface was examined in the absence and presence of excess calcium hydroxide. In both cases, the collector-surface interactions were impeded in the strong alkaline solution.