Potassium chloride

Fourier-Transform Infrared (FTIR) Spectroscopy Applications

Fourier-Transform Infrared (FTIR) spectroscopy is a powerful technique for identifying functional groups and molecular structures based on their vibrational modes. While pure, crystalline KCl exhibits minimal absorption in the mid-infrared region due to its simple ionic lattice, FTIR is invaluable for analyzing KCl in mixtures or as part of composite materials. In sample preparation for FTIR, KCl can be used as a matrix material for transmission spectroscopy, particularly when KBr is unsuitable due to hygroscopicity or potential halogen exchange reactions with chlorides jascoinc.comshimadzu.com. Research has shown that KCl can be detected and its presence confirmed in various matrices, such as geopolymers, where it appears as a distinct peak, often around 1096 cm⁻¹ researchgate.net. FTIR can also indicate the presence of KCl in doped crystals, with modest shifts in absorption frequencies observed due to doping researchgate.net.

UV-Visible Spectroscopy in KCl Nanoparticle Characterization

UV-Visible (UV-Vis) spectroscopy is primarily used to study electronic transitions in molecules and materials, often related to conjugation or band gaps. For this compound nanoparticles, UV-Vis spectroscopy can provide information about their optical properties and electronic band structure. Studies on green synthesized potassium oxide nanoparticles (KO NPs) derived from KCl have shown that the absorption edge exhibits a blueshift, indicating an energy gap (Eg) ranging from 2.8 to 3.4 eV sciencetechindonesia.com. This blueshift is characteristic of quantum confinement effects in nanomaterials. Similarly, research on KCl-doped KAP crystals indicates that KCl addition can influence the optical properties, with UV-Vis studies revealing improved transparency and changes in band gaps, suggesting the presence of indirect and direct transitions scirp.org. The technique is also employed to characterize synthesized KCl nanoparticles, providing insights into their optical behavior researchgate.netresearchgate.net.

Raman Spectroscopy for Aqueous Solution Structure Studies

Raman spectroscopy is highly sensitive to molecular vibrations and is widely used to study the structure and interactions within aqueous solutions. For this compound in aqueous solutions, Raman spectroscopy, often in conjunction with molecular dynamics simulations, provides insights into the disruption of water's hydrogen bonding network by ions. Studies have indicated that as KCl concentration increases, the hydrogen bonds between water molecules are disturbed, with the intensity of certain spectral patterns decreasing aidic.it. Research suggests that chloride ions (Cl⁻) disrupt the tetrahedral hydrogen bond network more significantly than sulfate ions (SO₄²⁻) in mixed solutions dntb.gov.uamdpi.comnih.govresearchgate.net. Furthermore, Raman spectroscopy can help identify ion pair formation in KCl solutions, where the perturbation on the spectra is influenced by the degree of ion pairing, which is found to be more substantial for KCl than for NaCl acs.orgresearchgate.net.

Atomic Absorption Spectroscopy for Vapor Detection

Atomic Absorption Spectroscopy (AAS) is a quantitative technique used to determine the concentration of metallic elements in a sample. It is particularly useful for detecting potassium, which is a key component of KCl. In the context of KCl, AAS can be employed to detect potassium atoms released from vaporized KCl. Techniques like collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) utilize UV lasers to dissociate KCl molecules into atomic potassium, which is then detected by AAS diva-portal.orgresearchgate.netoptica.org. This method allows for sensitive and selective detection of KCl vapor, with detection limits in the parts per billion (ppb) range demonstrated optica.org. Flame AAS and Graphite Furnace AAS (GF AAS) are common configurations, with GF AAS offering significantly lower detection limits due to enhanced atomization and longer residence times for the atoms in the light path vscht.cztu-clausthal.deresearchgate.net.

Powder X-ray Diffraction for Crystalline Nature and Structure

Powder X-ray diffraction (PXRD) is extensively used to confirm the crystalline nature of KCl and to identify its crystal structure. KCl typically crystallizes in the rock-salt (B1) structure, which is a face-centered cubic (FCC) lattice with a basis of K⁺ and Cl⁻ ions at specific positions hu.edu.joncku.edu.twchegg.combyjus.com. PXRD patterns of KCl exhibit characteristic diffraction peaks at specific 2θ angles, which correspond to the d-spacings determined by Bragg's Law. For instance, diffraction peaks at angles such as 28.26°, 40.51°, 50.16°, 58.46°, 66.31°, and 73.81° have been indexed to the (200), (220), (222), (400), (420), and (422) planes, respectively, matching the standard JCPDS Card number 41-1476 for KCl researchgate.net. Studies on synthesized KCl nanoparticles also confirm their crystalline nature through XRD, with average crystallite sizes reported, for example, at 108 nm for KO NPs derived from KCl sciencetechindonesia.com. In cases of doping or forming mixed crystals, XRD is crucial for verifying the incorporation of dopants and determining changes in lattice parameters, such as in KCl-doped KAP crystals or KCl-KBr mixed crystals scirp.orgnanochemres.orgscholarsresearchlibrary.com. The analysis of XRD patterns allows for the determination of lattice constants and confirmation of phase purity, as seen in studies of tris thiourea this compound crystals which confirmed an orthorhombic structure irphouse.com.

Single Crystal X-ray Diffraction for Cell Parameters

Single crystal X-ray diffraction (SCXRD) is a powerful technique for elucidating the precise three-dimensional arrangement of atoms within a crystal, including the determination of its unit cell parameters. For this compound, SCXRD has confirmed its common crystallographic structure. Under ambient conditions, KCl adopts a face-centered cubic (fcc) structure, commonly referred to as the B1 phase, analogous to that of sodium chloride nih.govwikipedia.org. This structure is characterized by a lattice constant, which represents the length of the unit cell edge. For KCl, this lattice constant is approximately 6.3 Å nih.govwikipedia.org. More precise measurements have reported values around 6.2952 Å for KCl crystals grown in halite–sylvite brine solutions worldscientific.com, and a lattice parameter of 3.14 Å for KCl at room temperature, with a value of 3.116 Å at 0 K ucl.ac.uk. It is important to note that under high pressure, KCl can adopt different polymorphic and hydrated phases, such as KCl·H₂O, which exhibits a monoclinic structure with specific lattice parameters (a = 5.687(7) Å, b = 6.3969(3) Å, c = 8.447(3) Å, and β = 107.08(8)°) researchgate.netresearchgate.netiucr.org. These studies highlight the sensitivity of KCl's crystalline structure to external conditions.

X-ray Scattering in Aqueous Solution Microstructure Studies

X-ray scattering techniques, including Small-Angle X-ray Scattering (SAXS) and Wide-Angle X-ray Scattering (WAXS), are invaluable for investigating the microstructure and ion behavior of substances in solution. Studies employing X-ray scattering on aqueous this compound solutions have provided insights into ion hydration, ion pairing, and the disruption of water's hydrogen bond network. Research has shown that as KCl concentration increases in aqueous solutions, the main peak in the pair distribution function (G(r)) shifts, indicating changes in the local ordering of ions and water molecules dntb.gov.uamdpi.comnih.gov. Specifically, the main peak, initially observed around 2.81 Å for certain interactions, can shift to approximately 3.15 Å with increased KCl concentration, suggesting the formation of K⁺-Cl⁻ ion pairs or altered K⁺-OW (water) interactions dntb.gov.uamdpi.comnih.gov. These studies also indicate that KCl disrupts the tetrahedral hydrogen bond network of water, with the strength of this disruption being influenced by the concentration of KCl mdpi.comnih.govresearchgate.netresearchgate.net. For instance, higher KCl concentrations lead to a decrease in the coordination number of water-water interactions, confirming the disruption of the hydrogen bond network mdpi.comnih.govresearchgate.net.

Scanning Electron Microscopy (SEM) for Morphology

Scanning Electron Microscopy (SEM) is a widely used technique for examining the surface morphology and microstructure of crystalline materials. SEM analysis of this compound crystals reveals their characteristic shapes, which can be influenced by crystallization conditions. In pure water, KCl crystals have been observed to predominantly grow with {100} faces, exhibiting a cubic habit researchgate.netresearchgate.net. Studies have also noted the formation of dendritic-type crystals alongside cubic particles in certain preparations nsf.gov. For example, SEM images have shown KCl crystals obtained from solutions at concentrations of 5.5 and 5.8 mol/L in pure water, displaying cubic morphology researchgate.netresearchgate.net. The presence of impurities, such as sodium chloride, can significantly alter the surface morphology of KCl, leading to the formation of co-crystals with different crystallographic orientations on the KCl surface worldscientific.com.

Energy-Dispersive X-ray Spectroscopy (EDS) for Elemental Analysis

Energy-Dispersive X-ray Spectroscopy (EDS), often coupled with SEM, is a crucial technique for determining the elemental composition of a sample. EDS analysis of this compound samples unequivocally confirms the presence of potassium (K) and chlorine (Cl) as the primary elements nsf.govmdpi.comresearchgate.netresearchgate.net. EDS spectra acquired from KCl samples typically show characteristic peaks for K and Cl, verifying the material's identity and purity nsf.govmdpi.com. For instance, EDS analysis of electrosprayed KCl targets has shown compositions with K at approximately 49.3 at.% and Cl at 48.4 at.%, with minor amounts of oxygen (2.3 at.%) nsf.gov. In other studies, EDS analysis of sylvite (KCl) minerals has confirmed that K and Cl are present in proportions of about 40% by weight, indicating a high concentration of KCl mdpi.com. EDS is also valuable for identifying impurities or contaminants within KCl samples, providing a comprehensive elemental profile mdpi.comresearchgate.net.

This compound as a Conductivity Standard in Analytical Chemistry

This compound (KCl) is widely recognized and utilized as a primary standard for calibrating conductivity meters and for general conductivity measurements in analytical chemistry. Its suitability stems from its high solubility, chemical stability, and the fact that it completely dissociates into potassium (K⁺) and chloride (Cl⁻) ions in aqueous solutions, leading to well-defined and reproducible conductivity values industrialpharmacist.comfishersci.no.

Standard KCl solutions are prepared at specific concentrations and temperatures, with traceability to national metrology institutes like NIST or PTB industrialpharmacist.comqasac-americas.orghach.comxylemanalytics.comscharlab.comwordpress.comhach.com. Common standard concentrations include 0.001 M (approximately 147 µS/cm at 25°C), 0.01 M (approximately 1413 µS/cm at 25°C), and 0.1 M (approximately 12880 µS/cm at 25°C) industrialpharmacist.comqasac-americas.orgxylemanalytics.comhach.com. These solutions are used to calibrate conductivity instruments, ensuring accurate measurements of unknown samples. The calibration process typically involves measuring the conductivity of at least two standard solutions to establish a calibration curve or to determine the cell constant of the conductivity probe qasac-americas.orginstrumentchoice.com.au. Accurate temperature control is paramount, as conductivity is highly temperature-dependent, with values typically reported at 25°C qasac-americas.orginstrumentchoice.com.au.

Data Tables

Table 1: Typical Lattice Parameters of this compound

Table 2: Standard Conductivity Values for this compound Solutions at 25°C

Note: Some sources provide a range or approximate value for conductivity. The table aims to represent the common values cited.

Compound Names Mentioned:

Chronoamperometry in Corrosion Studies

Chronoamperometry is an electrochemical technique that measures the current as a function of time at a constant applied potential. In corrosion studies, it is employed to investigate the kinetics of electrochemical reactions occurring on a metal surface, such as oxidation or reduction processes, and to understand how environmental factors influence these reactions.

The presence of this compound (KCl) in corrosive environments can significantly impact the electrochemical behavior of metals. Increased KCl concentration enhances the ionic conductivity of the electrolyte, which facilitates ion transport and thereby improves the kinetics of electrochemical reactions mdpi.com. Chloride ions (Cl⁻) are particularly notorious for their ability to penetrate protective oxide layers on metals, promoting the formation of soluble corrosion products and leading to continuous metal oxidation and localized corrosion, such as pitting mdpi.com. Chronoamperometric measurements can quantify these effects by observing changes in current density over time at specific potentials, revealing accelerated oxidation rates or the initiation of pit formation in the presence of KCl mdpi.comresearchgate.netiapchem.org. For instance, studies have shown that KCl can amplify current density and reduce charge transfer resistance, thereby enhancing electrodeposition kinetics and potentially increasing corrosion rates under certain conditions iapchem.org. In high-temperature environments, KCl has been shown to strongly accelerate corrosion by reacting with protective oxide layers to form chromates, which degrade the oxide's protective properties researchgate.net.

Study of Aqueous Solution Structure and Dynamics

Molecular dynamics simulations have been extensively used to investigate the structural and dynamic properties of this compound in aqueous solutions across a wide range of concentrations aidic.itacs.orgnih.govtandfonline.com. These studies reveal that KCl significantly influences the structure and dynamics of water molecules. At low concentrations (e.g., 0.01 M to 0.10 M), the structure of bulk water remains relatively steady, with hydrogen bonding interactions largely unaffected compared to pure water aidic.it. However, as the concentration increases (e.g., above 0.50 M), KCl begins to disturb the hydrogen bond network of water molecules, leading to a decrease in the percentage of hydrogen-bonded OH groups and a weakening of hydrogen bonding interactions aidic.itmdpi.com. This disruption is attributed to the hydration of K⁺ and Cl⁻ ions, which alters the local water structure and dynamics aidic.itresearchgate.net.

The dynamics of ions and water molecules are also affected. Simulations show that increasing KCl concentration can lead to changes in diffusion coefficients and altered hydrogen bond lifetimes for water molecules aidic.itresearchgate.net. The coordination numbers of ions, representing the average number of water molecules or other ions in their immediate vicinity, are also key structural parameters investigated. For K⁺ ions, coordination numbers typically range from approximately 5.7 to 6.5, depending on concentration and simulation conditions aidic.itmdpi.comacs.org. For instance, at a concentration of 2.00 M, the coordination number of K⁺ decreases to 5.73, indicating a more structured first hydration shell aidic.it. Similarly, the first shell coordination numbers for Cl⁻ ions have been reported to range from 5.90 to 6.53 across various concentrations aidic.itmdpi.com.

Data Table 1: Coordination Numbers of K⁺ Ions in KCl Aqueous Solutions

Note: Data derived from molecular dynamics simulations at 298 K aidic.it.

Ion-Cluster Formation and Lifetimes in Supersaturated Solutions

In supersaturated solutions of this compound, molecular dynamics simulations have provided evidence for the formation of transient ion clusters acs.orgnih.govaip.orgacs.orgresearchgate.net. These clusters are dynamic aggregates of ions that exist for finite periods before dissociating or potentially growing into larger structures. Studies suggest that these clusters can form in the prenucleation phase, particularly as the concentration approaches or exceeds the saturation limit acs.orgresearchgate.net.

Simulations indicate that in supersaturated regimes, structures with relaxation times ranging from picoseconds to up to 100 picoseconds can be observed acs.orgnih.govaip.org. The formation and lifetimes of these ion clusters are influenced by the degree of supersaturation and other factors such as temperature acs.orgnih.gov. For example, research has suggested that transient structures in supersaturated KCl solutions can have relaxation times on the scale of 5–100 ps acs.orgnih.gov. The dynamics within these highly clustered solutions can exhibit collective behavior, characterized by stretched exponential decay of the self-intermediate scattering function acs.orgnih.gov. The precise definition and characterization of these clusters, including their size distribution and lifetimes, are areas of ongoing investigation within MD simulations acs.orgaip.org.

Data Table 2: Ion Cluster Lifetimes in Supersaturated KCl Solutions

Hydrogen Bonding Interactions in KCl Aqueous Solutions

The influence of this compound on the hydrogen bonding network of water molecules is a significant aspect studied through molecular dynamics simulations. Ions in solution interact with water molecules, forming hydration shells and affecting the existing water-water hydrogen bonds aidic.itresearchgate.netresearchgate.net.

Simulations show that while dilute KCl solutions (below 0.10 M) exhibit hydrogen bonding patterns similar to pure water, higher concentrations lead to a notable disturbance of the water's hydrogen bond network aidic.itmdpi.com. In concentrated KCl solutions, the tetrahedral hydrogen-bonded water network is progressively weakened and disrupted mdpi.comresearchgate.net. This disruption is quantified by changes in hydrogen bond lifetimes and coordination numbers, indicating a decrease in the number of water-water hydrogen bonds and an increase in ion-water interactions aidic.itresearchgate.netresearchgate.net. For instance, studies indicate that as KCl concentration increases, the coordination number of water-water (OW-OW) decreases, suggesting a severe damage to the tetrahedral network mdpi.comresearchgate.net. The nature of ion-water hydrogen bonding, including the strength and geometry of these interactions, is also a focus of these simulations.

Coordination Numbers of Ions in Solution

Coordination numbers are fundamental parameters in describing the solvation structure of ions in aqueous solutions. They represent the average number of solvent molecules (water) or counter-ions directly surrounding a central ion. Molecular dynamics simulations provide detailed insights into these coordination numbers for K⁺ and Cl⁻ ions in KCl aqueous solutions.

As detailed in section 4.5.1, the coordination number of K⁺ ions with water molecules typically falls within the range of 5.7 to 6.5, with variations observed across different concentrations aidic.itmdpi.comacs.org. For example, simulations show a decrease in the K⁺ coordination number from 6.43 at 0.01 M to 5.73 at 2.00 M aidic.it. Similarly, the first shell coordination numbers for Cl⁻ ions with water molecules are reported to be around 6.4 to 6.5 at lower concentrations, decreasing to 5.90 at 2.00 M aidic.it. In some studies, the coordination of K⁺ ions by chloride ions (K⁺-Cl⁻) has also been investigated, with values increasing with concentration, indicating the formation of ion pairs mdpi.comresearchgate.net. For instance, in 4 molal aqueous KCl solution, the coordination number of water molecules around K⁺ was found to be 6.1, with an additional 0.8 chloride ions also in the first coordination shell acs.org.

Compound List

this compound (KCl)

Intracellular Solutions for Patch-Clamp Recordings

The patch-clamp technique is a powerful method for studying ion channels in biological membranes. Intracellular solutions used in whole-cell patch-clamp recordings are formulated to replicate the ionic composition found inside a typical cell. Potassium chloride is a common constituent of these internal solutions, often used at high concentrations (e.g., 130-150 mM) to mimic the high intracellular potassium concentration relative to the extracellular environment. A KCl-based pipette solution is noted for minimizing liquid-liquid junction potentials, which can occur at the interface between the pipette solution and the extracellular fluid, and can lead to lower pipette resistance. This contributes to more stable and accurate recordings of ionic currents and membrane potential changes. axolbio.comuk.comjneurosci.orglabome.comnih.govuk.com

Inducing Cell Membrane Depolarization in vitro

Elevated extracellular concentrations of this compound are widely employed in vitro to induce the depolarization of neuronal cell membranes. Depolarization is a critical process in cell signaling, particularly in excitable cells like neurons, where it underlies the generation of action potentials. By increasing the extracellular potassium concentration, the electrochemical gradient for potassium ions across the cell membrane is reduced. This shift in gradient facilitates the influx of positive charge (or reduces the efflux of positive charge), leading to a less negative (more depolarized) membrane potential. Concentrations ranging from 3 mM to 150 mM have been used, with 50-55 mM KCl often cited as a standard treatment for inducing robust gene expression and studying activity-regulated signaling pathways. This method allows researchers to investigate calcium influx through voltage-sensitive calcium channels and other downstream cellular responses triggered by membrane depolarization. nih.govnih.govtandfonline.comresearchgate.nettechnologynetworks.commdpi.comphysiology.org

Calibration and Verification of Conductivity Equipment

Conductivity meters measure the ability of a solution to conduct electricity, which is directly related to the concentration and mobility of ions present. KCl solutions of precisely known concentrations are used to calibrate these instruments. Standard solutions are prepared with specific molalities or molarities, such as 0.001 mol/kg, 0.1 mol/kg, or 0.1 M, and their conductivity values at a reference temperature (typically 25 °C) are well-established and traceable to national standards like those from NIST. For example, a 0.001 M KCl solution has a conductivity of approximately 147 µS/cm at 25 °C. Calibration involves measuring these standard solutions to ensure the instrument reads accurately across its range, allowing for precise measurements of unknown sample conductivities in various applications, from environmental monitoring to quality control. scharlab.comwordpress.comqasac-americas.orgfishersci.noavantorsciences.comhach.comnilu.nosigmaaldrich.comriccachemical.comvwr.com

Reference Material in Titration Methods

In analytical chemistry, particularly in potentiometric titrations, KCl serves as a reference material. It is used as a supporting electrolyte in solutions where it does not interfere with the titration reaction but contributes to maintaining a stable ionic strength and conductivity. For instance, it is used as a filling solution for reference electrodes (e.g., silver/silver chloride or calomel electrodes) in pH, redox, and ion measurements, ensuring a stable reference potential. fishersci.sebipm.orgreagecon.comachrom.benih.gov

Electrospraying Deposition and Annealing

This compound has been utilized in electrospraying deposition techniques to create targets for nuclear science measurements nsf.govosti.govlanl.gov. This process involves preparing specialized KCl solutions, often employing a solvent mixture that includes deionized water, glycerol, and 2-methoxyethanol to achieve optimal viscosity for spraying nsf.gov. The electrospraying is typically performed onto thin gold backings, resulting in the deposition of KCl as relatively large, discrete particles rather than continuous films nsf.govosti.govlanl.gov.

Following deposition, a short annealing step is applied, usually in a preheated furnace at temperatures ranging from 350 °C to 450 °C nsf.govosti.gov. This annealing process is crucial for preparing stable and robust targets, enabling the production of materials that are challenging to fabricate using conventional methods nsf.govosti.gov. The electrospraying and annealing combination allows for the creation of targets with a tunable amount of KCl on the backings nsf.gov.

Characterization of Targets (XRF, SEM, EDS)

This compound is recognized for its utility as a standard in several analytical characterization techniques, including X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Spectroscopy (EDS).

X-ray Fluorescence (XRF) KCl is employed as a primary standard for the quantitative determination of chloride content, often calibrated using XRF spectrometry nist.gov. While analyzing materials containing chlorine via XRF presents challenges due to the element's volatility during fusion processes, methods have been developed to achieve high precision, with calibration errors for chlorine as low as 0.25% reported fluxana.de. Furthermore, KCl is used in XRF-based methods for determining chloride levels in building materials like cement researchgate.net.

Scanning Electron Microscopy (SEM) SEM is instrumental in visualizing the morphology of KCl deposits. Studies using electrospraying have shown that KCl forms distinct particles, sometimes exhibiting dendritic structures, on substrate surfaces nsf.govosti.govlanl.gov. SEM also proves effective in identifying KCl when present as a contaminant on various materials, such as paper products semlab.comsemlab.com.

Energy-Dispersive X-ray Spectroscopy (EDS) EDS analysis is routinely used in conjunction with SEM to ascertain the elemental composition of KCl targets and particles nsf.govmdpi.combibliotekanauki.plmdpi.com. For instance, EDS analysis of particles generated via electrospraying has revealed elemental compositions such as approximately 49.3 at.% Potassium (K), 48.4 at.% Chlorine (Cl), and 2.3 at.% Oxygen (O) nsf.gov. This technique is vital for confirming the presence and distribution of potassium and chlorine in research samples.

Data Tables

Table 1: Elemental Composition of Electrosprayed KCl Particles (EDS Analysis)

Note: Data adapted from nsf.gov. Composition of dendritic crystals is described as similar to large particles, with EDS spectra showing intense gold peaks compared to particles, suggesting dendrites are thinner.

Table 2: this compound as a Standard in Analytical Techniques