Aqueous Solutions Of Sodium Fluoride Research Articles

Partial molar volume and partial molar compressibility of four homologous α-amino acids in aqueous sodium fluoride solutions at different temperatures

Density and ultrasonic speed of four amino acids (glycine, l-alanine, l-valine, and l-leucine) in aqueous sodium fluoride solutions {(0.1 to 0.5) M} have been measured at T = (308.15, 313.15, and 318.15) K. Apparent molar volumes ( V φ ), partial molar volumes V φ 0 , transfer volumes Δ V φ 0 and hydration number ( n H ) are evaluated using density data. Adiabatic compressibility ( β s), change (Δ β s), and relative change in compressibility (Δ β s/ β 0), apparent molar compressibility ( K φ ), partial molar compressibility K φ 0 , transfer compressibility Δ K φ 0 , and hydration number ( n H) have been calculated using ultrasonic speed data. The linear correlation of V φ 0 , Δ V φ 0 , K φ 0 and Δ K φ 0 for a homologous series of amino acids have been used utilised to calculate the contribution of charged end groups ( NH 3 + , COO −), CH 2 group and other alkyl chain of the amino acids. The analysis shows that the ion–ion interactions are much stronger than ion–hydrophobic interactions over the entire concentration range of sodium fluoride. It is observed that sodium fluoride has a strong dehydration effect on amino acids.

Growth and Characterization of Non-Linear Optical Material

An organic nonlinear optical (NLO) single crystal has been synthesized by slow solvent evaporation technique from aqueous solutions of L-serine and sodium fluoride (NaF) at ambient temperature. The grown crystal was confirmed by single crystal X-ray diffraction analysis. The powder X-ray diffraction of the grown crystal was recorded and indexed. The functional groups of the grown crystals were determined by FTIR spectrum. The optical absorption study reveals that the transparency of the crystal in the entire visible region and the lower edge was found to be 258 nm. Relative powder second harmonic generation (SHG) efficiency of the grown crystal was tested by Kurtz and Perry powder technique using high intensity Nd:YAG laser operating at 1064 nm.

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

Objectives To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. Methods Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm × 3 mm area) before being randomly allocated to 1 of 5 groups per substrate ( n = 10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle = artificial saliva (2 h, pH 7.0) + erosion (0.3% citric acid, pH 3.2, 5 min) + fluoride/control (5 min) + attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in μm was measured using optical profilometry. Results When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. Conclusions The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.

Electrocapillary maximum and potential of zero charge of carbon aerogel

We present an electrochemical study of carbon aerogel (CA) in aqueous sodium fluoride solutions, focusing on the comparison of two quantities that are related to the potential of zero charge (pzc): the capacitance minimum and the 'electrocapillary maximum' of the surface forces. Capacitance minima are well resolved in our samples. Their potential emerges reproducibly as around 90 mV (vs. Ag/AgCl in KCl), similar to the value, 70 mV, of bulk glassy carbon which we use for comparison, and similar to previous reported pzc values for carbon materials. Significantly, no electrocapillary maximum is found in this potential range. This demonstrates that the pzc does not necessarily coincide with the potential of the maximum of surface stress. We also determined the area-specific capacitances, c(a) = 2.8 microF cm(-2), which agrees well with reports for the basal-plane of graphite single crystals. Our experiments yield large reversible strain amplitudes, up to 0.45%.

Adsorption behavior of fluoride ions using a titanium hydroxide-derived adsorbent

Abstract The removal behavior of fluoride ions was examined in aqueous sodium fluoride solutions using a titanium hydroxide-derived adsorbent. The adsorbent was prepared from titanium oxysulfate (TiOSO4·xH2O) solution, and was characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry–differential thermal analysis, Fourier transform infrared spectrum and specific surface area. Batchwise adsorption test of prepared adsorbent was carried out in aqueous sodium fluoride solutions and real wastewater containing fluoride ion. The absorbent was the amorphous material, which had different morphology to the raw material, titanium oxysulfate, and the specific surface area of the adsorbent (96.8 m2/g) was 200 times higher than that of raw material (0.5 m2/g). Adsorption of fluoride on the adsorbent was saturated within 30 min in the solution with 200 mg/L of fluoride ions, together with increasing pH of the solution, due to ion exchange between fluoride ions in the solution and hydroxide ions in the adsorbent. Fluoride ions were adsorbed even in at a low fluoride concentration of 5 mg/L; and were selectively adsorbed in the solution containing a high concentration of chloride, nitrate and sulfate ions. The adsorbent can remove fluoride below permitted level (

Consistency of Ion Adsorption and Excess Surface Tension in Molecular Dynamics Simulations of Aqueous Salt Solutions

Molecular dynamics simulations of the liquid−vapor interface of aqueous solutions of sodium fluoride and of sodium iodide have been carried out using nonpolarizable force fields for ions and water molecules. Despite the absence of explicit polarizability, the tendency of iodide ions to show an enhanced concentration at the surface that was reported for polarizable force fields (Jungwirth, P.; Tobias, D. J. J. Phys. Chem. B 2001, 105, 10468) is reproduced, while sodium and fluoride ions prefer the interior of the bulk liquid. These observations are confirmed by the contributions of the different species to the surface potential. The systems we study here are much larger than the ones investigated in previous simulations by other authors, which enables us to calculate the adsorption of ions at the interface from the density profiles and subsequently—via Gibbs’ adsorption isotherm—the corresponding excess surface tension over that of pure water. The so-obtained values for the surface tension are compared with the results calculated directly from the normal and lateral components of the pressure tensor in the simulation. Consistency is found among the data, but the directly obtained values have significantly larger error bars and are intrinsically more scattered. The Gibbs adsorption isotherm thus not only is a thermodynamic requirement to be met but also offers a reliable and less error-prone way of calculating the surface tension increment from density profiles.

New Insights into Structural Alteration of Enamel Apatite Induced by Citric Acid and Sodium Fluoride Solutions

Attenuated total reflectance infrared spectroscopy and complementary scanning electron microscopy were applied to analyze the surface structure of enamel apatite exposed to citric acid and to investigate the protective potential of fluorine-containing reagents against citric acid-induced erosion. Enamel and, for comparison, geological hydroxylapatite samples were treated with aqueous solutions of citric acid and sodium fluoride of different concentrations, ranging from 0.01 to 0.5 mol/L for citric acid solutions and from 0.5 to 2.0% for fluoride solutions. The two solutions were applied either simultaneously or consecutively. The citric acid-induced structural modification of apatite increases with the increase in the citric acid concentration and the number of treatments. The application of sodium fluoride alone does not suppress the atomic level changes in apatite exposed to acidic agents. The addition of sodium fluoride to citric acid solutions leads to formation of surface CaF2 and considerably reduces the changes in the apatite P-O-Ca framework. However, the CaF2 globules deposited on the enamel surface seem to be insufficient to prevent the alteration of the apatite structure upon further exposure to acidic agents. No evidence for fluorine-induced recovery of the apatite structure was found.

Surface modification of titanium for load-bearing applications

Titanium and its alloys are extensively used in load-bearing metallic devices. They are bioinert material and, therefore, get encapsulated after implantation into the living body by a fibrous tissue that isolates them from the surrounding tissues. Here we report modification of titanium surface using bioactive tricalcium phosphates (TCP) and nanoscale TiO2 to enhance cell-materials interaction. We have introduced bioactivity in Ti using laser-assisted coating of TCP and by anodization to grow surface TiO2 at room temperature using a mixed aqueous solution of sodium fluoride, citric acid and sulfuric acid as electrolyte. TCP coating showed a columnar Ti grains at the substrate side of the coating and transitioned to an equiaxed grains at the outside. Coating hardness increased from 882 +/- 67 to 1029 +/- 112 Hv as the volume fraction of TCP increased in the coating. For TiO2 nanotubes, microscopic analysis showed tubes of 50 nm in diameter with wall thickness of 15 nm and typical length between 200 nm and 1 micron based on anodization times. Effects of TCP and nanoscale TiO2 coating on bone cell-material interaction were examined by culturing osteoprecursor cells (OPC1) on coated surfaces. Antibacterial activity analysis using metallic Ag via electrodeposition showed over 99% antibacterial activity against the growth of colonies of Pseudomonas aeruginosa.

Salient features of the electrical double layer structure on mechanically renewed gold-silver electrodes in aqueous solutions of a surface-inactive electrolyte

The behavior of electrodes, which are made of binary Au-Ag alloys (Ag content 1–15 at %) and renewed by mechanical cutting in aqueous solutions of sodium fluoride, is studied with the aid of cyclic voltammetry and impedance methods. It is established that, in the region of potentials corresponding to ideal polarizability, the differential capacitance of the electrical double layer rapidly changes with time elapsed after the renewal of the surface of the electrodes. The change in the capacitance is brought about by the exit of silver atoms into a surface layer. The implication is that silver is the surface-active component in these alloys. The rate of the surface segregation of silver atoms depends on the electrode potential. The segregation rate substantially increases upon going into the region that corresponds to positive charges of the silver electrode surface and to the beginning of adsorption of atomic oxygen on the electrode. Based on phenomenological models, a method for processing capacitance curves is realized, which links experimentally observed time effects to variations that occur in the surface composition, and assumptions concerning the mechanism of relaxation processes that are responsible for the observed time effects are put forth. Explicit data on the effect, which is exerted by mechanical renewal on the composition of the surface layer of Au-Ag alloys at different distances from the interface with a vacuum, are obtained with the aid of an x-ray photoelectron spectroscopy method. It is established that the surface layer (∼0.5 nm) is enriched by silver atoms as compared with the alloy’s bulk.

Non-ideality and ion-pairing in saturated aqueous solution of sodium fluoride at 25 °C

Using Solvent Evaporating and Atomic Emission Spectrophotometric methods, the solubility of NaF in water at 25 °C was determined. Comparing the value of the thermodynamic solubility product constant, K sp(th), ( K sp(th) = exp(− Δ G diss° / RT)) of NaF to the value which is obtained from the observed solubility, s/mol L −1 , and activity coefficients, f + and f −, which are estimated upon the extended Debye–Hückel law, K sp′ = [Na +][F −] f + f −, revealed a great difference. The difference has satisfactorily been explained using a combination of Debye–Hückel law and Ion-Association Theory.

An electrochemical study of the oxidation of 1,3,5-Tris[4-[(3-methylphenyl)phenylamino]phenyl]benzene

An investigation into the oxidative electrochemistry of 1,3,5-Tris[4-[(3-methylphenyl)phenylamino]phenyl]benzene (TMPB) is described. In particular, the heterogeneous electron-transfer kinetics in N, N-dimethylformamide (DMF) and dichloromethane (DCM) are studied using the high-speed microband channel electrode. Experiments to investigate the standard electrochemical rate constants, k 0, transfer coefficients, α, and formal potentials, E f 0, of the observable oxidations of TMPB in both DMF and DCM solutions containing 0.10 M tetrabutylammonium perchlorate (TBAP) are reported for 12.5 μm platinum microband electrodes using a range of linear flow velocities from 12 to 25 m s −1. The measured values of k 0 for the two measurable oxidations in DMF are 1.03 ± 0.41 and 1.02 ± 0.20 cm s −1, and for the three oxidations in DCM are 0.44 ± 0.04, 0.17 ± 0.03 and 0.08 ± 0.02 cm s −1, respectively. The values of α for these oxidations in DMF are 0.48 ± 0.06 and 0.52 ± 0.02, and in DCM are 0.52 ± 0.02, 0.62 ± 0.03 and 0.53 ± 0.07, respectively. The respective formal oxidation potentials (all measured vs Ag) are 0.533 ± 0.002 and 0.766 ± 0.003 V in DMF, and 0.161 ± 0.002, 0.495 ± 0.002 and 1.128 ± 0.004 V in DCM. The presence of the monocation radical in DCM is confirmed by ESR measurement. Experiments are also presented to explore the voltammetry of TMPB in microdroplets of toluene and also in the solid-phase, when in contact with aqueous solutions of sodium fluoride, perchlorate, nitrate and sulphate. It was found that, when TMPB is dissolved in a toluene microdroplet, anion insertion accompanies the first oxidation for the case of perchlorate and nitrate, with anion-facilitated dissolution occurring for sulphate and fluoride. More complex reactions occur at more positive potentials. In the solid-phase, however, slow anion-facilitated dissolution still occurs for fluoride and sulphate, and rapid direct dissolution takes place in the case of perchlorate.

Amiodarone Attenuates Fluoride‐induced Hyperkalemia in Vitro

AbstractPoisoning by hydrofluoric acid or fluoride salts results in hypocalcemia, hypomagnesemia, and hyperkalemia with subsequent cardiac dysrhythmias. In previous studies, quinidine attenuated fluoride‐induced hyperkalemia in vitro, and enhanced survival in animals. Like quinidine, amiodarone is a potassium channel blocker, although amiodarone is more familiar to clinicians due to its recent inclusion in advanced cardiac life support (ACLS) protocols. Objectives: This in‐vitro study of human erythrocytes was designed to determine whether amiodarone could attenuate fluoride‐induced hyperkalemia. Methods: Six healthy volunteers each donated 60 mL of blood on three occasions. Each specimen was divided into 12 tubes, incubated at 37°C, and oxygenated with room air. An aqueous sodium fluoride (F−) solution was added to tubes 1–9. Incremental amounts of quinidine were added to tubes 1–4 (Q1–Q4) to attain calculated concentrations of 0.73 μg/mL, 1.45 μg/mL, 2.9 μg/mL, and 5.8 μg/mL, respectively. Incremental amounts of amiodarone were added to tubes 5–8 (A1–A4) to attain calculated concentrations of 0.38 μg/mL, 0.75 μg/mL, 1.5 μg/mL, and 3.0 μg/mL, respectively. Tubes 9–12 were controls for each of F−, amiodarone, quinidine alone, and no additive, respectively. Extracellular potassium concentration ([K+]) was followed, and an objective endpoint was defined as the rise in potassium concentration at 6 hours. Results: Fluoride produced a significant change in [K+] by 6 hours in all samples. Quinidine produced a J‐shaped curve in its ability to attenuate the rise in [K+], with only one concentration, Q3, demonstrating significance versus tube 9 (control). Amiodarone also demonstrated a J‐shaped dose–response effect, with statistical significance at A1, A2, and A3 versus tube 9 (control). There was no significant difference among the effective concentrations (Q3, A1, A2, and A3) of both drugs. Conclusions: In this in‐vitro model using human blood, amiodarone and quinidine both attenuated F−‐induced hyperkalemia. Further study is indicated to determine whether amiodarone enhances survival in F−‐poisoned animals.

Physicochemical Characterization of Porous Silicon Surfaces Etched in Salt Solutions of Varying Compositions and pH

AbstractWe prepared porous silicon (PSi) structures by standard electrochemical processes using aqueous sodium fluoride (NaF) solutions. We report the dependence of the porous structure on the variation of pH and salt concentration of the etching solution, and the applied current density. The PSi structures were characterized by Scanning Electron Microscopy (SEM) and Secondary Ion Mass Spectroscopy (SIMS) to determine the pore size and distribution and the surface chemical composition. Results obtained from SEM show that the PSi grown has two different structures depending on the current density. Low current densities produce a uniform, high-density arrangement of pores while high current densities yield a sponge-like structural network. SIMS results indicate that the porous framework is covered with a silicon oxide layer.

Determination of the surface charge density of a mercury electrode by extrusion: a new method for correction of the faradaic component

The accurate determination of the surface charge density at the mercury ∣ solution interface by the method of extrusion of mercury drops is impaired by the faradaic current caused by traces of electroactive species. This paper describes a new design of a hanging mercury drop electrode with accurate control of the extruded electrode area, to within 0.1%, together with a new and reliable procedure for correction of the faradaic current. The procedure is based on first obtaining the correction parameters in the presence of increasing amounts of electroactive species and then using these parameters for correction of the faradaic component so as to obtain the surface charge density of the electrode. Implementation of the method with a microcomputer controlled system provides automatic acquisition of corrected electrode charge density values as a function of the electrode potential. The results obtained with this new method are in excellent agreement with those obtained by other methods, as illustrated for aqueous sodium fluoride solution.

The Effects of Fluorides and/or Trace Elements on the Solubilities of Enamel and Cementum

The purpose of this study is to determine the effects of fluorides and trace elements applied alone or in combination at different concentrations on the solubilities of enamel and cementum surfaces of the same teeth. The study has been performed on enamel and cementum surfaces of the impacted third molars extracted by surgical operation. Aqueous solutions of sodium fluoride, aluminum potassium phosphate, strontium chloride and titanium tetrachloride at different concentrations were applied to the surfaces. The solubilities of enamel and cementum and the depth of etchings have been calculated by means of the inorganic phosphorus in these etching solutions. According to the results, higher concentrations of fluoride and lower concentrations of strontium and titanium led to a significant reduction into solubilities of enamel and cementum. As certain combined applications of fluorides and trace elements decreased both of the enamel and cementum solubilities, it may be assumed that if such a treatment is beneficial during the adolescence of an individual, it may also be used when he is older.

Calculation of outer Helmholtz potential at mercury as a function of temperature and concentration of aqueous sodium fluoride solutions

Abstract Potentials of the outer Helmholtz plane, o 2 , at mercury as function of electrode potential and temperature are calculated on the basis of the Gouy-Chapman theory using Grahame's data for surface charge and capacitance in aqueous NaF solutions. An empirical equation for calculating o 2 at negative rational potential is presented. Grahame's original data of surface charge and capacitance are summarized in ASCII files on floppy disk.

Enamel Fluoride Uptake Affected by Site of Application: Comparing Sodium and Amine Fluorides

In enamel fluoride uptake studies, the most frequently sampled site is the middle third of the buccal surface. Because different parts of the enamel surface vary in fluoride concentration, the present study investigated fluoride uptake at contrasting sites using two different topical agents. One was a neutral aqueous solution of sodium fluoride containing 2% w/w of fluoride, and the second was an aqueous solution of two amine fluorides containing 1% w/w of fluoride. The enamel of 10 pairs of clinically sound extracted human premolars was etched initially and after treatment with one of these agents on the cervical and middle thirds of the buccal surface and on the proximal surface, yielding the pre- and post-treatment fluoride concentrations of these sites at depths of 5 and 10 microns from the surface. Enamel treated with the amine F solution had significantly higher fluoride uptakes at all sites compared to the NaF-treated specimens. The differences in uptake from the two agents varied with site, being smallest for the buccal middle third enamel and greatest for the proximal enamel. It is suggested that these results relate to possible differences in enamel maturation or to the presence of initial proximal caries, and the greater affinity of amine fluoride for porous enamel. The findings emphasise the importance of obtaining site-specific data in the study of fluoride in enamel.

Weekly rinsing with a fluoride mouthrinse in an unfluoridated community: results after seven years.

In the fall of 1975, 1,915 children in grades K through eight began a school-based program of supervised weekly rinsing with 0.2 percent aqueous solution of sodium fluoride in an unfluoridated community in the Finger Lakes area of upstate New York. At baseline and annually thereafter, a random sample of children in grades K through 11 received clinical dental caries examinations. The prevalence of dental caries by grade at each of the follow-up dental examinations was compared to the grade-specific prevalence of dental caries at baseline. Overall, there was a decline of 57.8 percent in prevalence of caries in permanent teeth after seven years of rinsing. Among children in grades K through five, there was a decline of 35.4 percent in the prevalence of caries in primary teeth during the same time period. Tenth and eleventh grade children, after not rinsing for one and two years, respectively, continued to show the same trend toward lower caries prevalence as active rinsers. Caries prevalence among seventh and eighth graders after seven years of rinsing was not significantly different from caries prevalence among seventh and eighth grade lifetime residents of a nearby fluoridated community. A decline in the prevalence of caries in primary teeth among kindergartners prior to rinsing suggests that factors in addition to the mouthrinse program may have contributed to the decline in caries prevalence.

Self-gelling liquid composition for topical application of medications.

The present work was carried out to modify a self-gelling liquid composition for fluoride application to teeth so it would gel with reduced fluoride content. Past work had shown that quaternary ammonium compounds with carbon chain lengths in the C12 to C16 range or surface modifiers such as hydroxylamine-HCl in conjunction with surfactants facilitated gelation in systems of tetraethoxysilane and aqueous sodium fluoride solutions containing 1,900 ppm or more fluoride. A search was conducted among amines, imines and heterocyclic compounds for agents that would facilitate gelation in systems with lower fluoride concentrations. The findings were that imidazole-HCl in conjunction with a surfactant could effect gelation within minutes in systems with as little as 100 ppm fluoride and, further, that gelation of such systems was not affected by the presence of a series of disinfectants, antibiotics or hormones. Thus, it appears that the self-gelling system may be used as a vehicle for medicaments other than fluoride.

The use of sodium fluoride for the treatment of ear noise in patients with otosclerosis

In order to regulate the metabolic processes of bone tissue in otosclerosis and accelerate the maturation of otosclerotic foci, many authors use sodium fluoride [1, 3]. For the same purpose, patients with active and moderately active stages of otosclerosis before surgery are treated with 0.6% aqueous sodium fluoride solution inside at the rate of 1 mg per 1 kg of body weight for 2 months; in the form of endoaural electrophoresis with 1% solution for 15 sessions per ear and mixed treatment consisting of oral administration of the drug in combination with electrophoresis. Fluoride therapy was prescribed in two courses with an interval of 1 month. The results were judged according to noise measurement data. Statistical processing of the results of the study was carried out using the StudentFisher method.