H2O Electrolyte Research Articles

Detection of high energy particles using CR-39 detectors Part 2: Results of in-depth destructive etching analysis

We have performed Pd electrodeposition in both D2O and H2O electrolytes in the presence of a magnetic field using CR-39 solid state nuclear track detectors. These detectors were either immersed in the electrolyte or separated from it by a thin Mylar® film. We have found a statistically significant increase in the number of tracks measured in the D2O experiments when compared to the H2O experiments.

Synthesis of TiO<sub>2</sub> Nanotubes and the Effects of Deionized Water on their Surface Morphology and Microstructure

Nanotubes of TiO2 have been synthesized on titanium metal by DC anodization at 50 V in an EG/NH4F/D.I. H2O electrolyte. The anodization apparatus which uses a platinum cathode is unique and designed to allow only for a single-face anodization. The influence of deionized water (D.I. H2O) on the surface morphology of the nanotubes was investigated using the scanning electron microscope (SEM), while the microstructure before and after calcination was studied using X-ray diffraction technique (XRD). Results show that the surface density and uniformity of the TiO2 nanotube arrays varies with the percentage of D.I. H2O in the electrolyte. The best result was obtained at 6% vol D.I. H2O after calcination. This result is useful since, the surface morphology and microstructure play a vital role in the performance of TiO2 nanotubes in various applications.

Solid–Liquid Equilibrium on the Reciprocal Aqueous Quaternary System Li+, Mg2+//Cl–, and Borate–H2O at 323 K

The solid–liquid phase equilibrium in the reciprocal aqueous quaternary system Li+, Mg2+//Cl–, and borate–H2O at 323 K was completed with the isothermal dissolution method. The corresponding physiochemical properties (ρ, ηD) of solutions at equilibrium in the Li+, Mg2+//Cl–, and borate–H2O electrolyte mixtures were determined. The isothermal dissolution phase diagram, the water figure, and the figures for the physicochemical properties (ρ, ηD) depending on the composition were obtained according to values of the Janecke index. The stable phase diagram contains three invariant points, seven univariant curves, and five crystallization zones. The crystallographic forms of magnesium borate and lithium borate are tetraborate MgB4O5(OH)4·7H2O and Li2B4O7·3H2O, respectively. The size of MgB4O5(OH)4·7H2O crystallization field is the largest among the coexisting salts.

Annealing temperature-dependent crystallinity and photocurrent response of anodic nanoporous iron oxide film

Abstract

Investigation of Anatase-TiO2 As an Efficient Electrode Material for Magnesium-Ion Batteries

The advent of lithium-ion electrochemical has ushered in a new era of high energy density rechargeable batteries, with applications ranging from portable electronics to electric vehicles.1 However, several challenges have stymied the implementation of lithium-ion batteries that approach the thermodynamic capacity and energy density limit. This is largely associated with the use of a lithium-metal anode, which under extensive cycling conditions and current densities promotes the formation of dendritic lithium deposits. Lithium dendrites result in the formation of electrochemically “dead” lithium, resulting in poor cycling efficiency.2 In addition, dendritic lithium has been implicated in the cell shorting and thermal runaway. To mitigate such problems, alternative energy storage systems have been heavily pursued recently, with efforts largely focused on the development of sodium-ion and magnesium-ion electrochemical cells.3 The implementation of a magnesium metal anode is highly advantageous to lithium, as the volumetric capacity is nearly double (3833 mAh/mL vs. 2062 mAh/mL, respectively) and the deposition morphology is described as non-dendritic.2 As such, considerable attention has been focused the development of magnesium electrochemical cells utilizing a magnesium metal anode, high capacity cathode, and suitable electrolyte. One of the leading cathode materials is the Chevrel-phase Mo6S8, introduced in 2000 with an experimentally determined specific capacity of 105 mAh/g.4 Recently, Sheha described an anatase TiO2/ reduced graphene oxide (rGO) composite cathode material was used in a magnesium-ion electrochemical cell utilizing a Mg metal anode and polyvinyl alcohol/ MgBr2/ tetraglyme/ H2O electrolyte. This cathode was shown to maintain cyclability to fifty cycles. Following this report and the plethora of publications concerning the insertion electrochemistry of anatase-phase titanium dioxide, we decided to investigate the feasibility of TiO2/ carbon black/ poly tetrafluoroethylene (PTFE) as an electrode for magnesium-ion batteries. Herein, we report a study concerning the electrochemistry of Mg/TiO2 cells as well as a full characterization using spectroscopic and microscopic techniques. Figure 1 shows the voltage profiles of the TiO2/Mg coin cell with the All Phenyl Complex (APC) electrolyte between 0.05 and 2.2 V at a current density of 5 μA/ mg. During the first discharge, TiO2exhibits a well-defined plateau at approximately 0.5 V. The first discharge capacity is ~80 mAh/g. The material experiences a large polarization where the charge plateau increases to 1.2 V. The corresponding irreversible capacity in the first cycle is 20 mAh/g, which may arise from the poor conductivity of the electrode as well as the electrolyte side reactions. The close capacity between the discharge and charge process from the second cycle manifests excellent reversibility of the electrode. Figure 1 shows discharge and charge capacities with respect to cycle number at the same current density over 50 cycles. The capacity of the electrode remains at a quite considerable value after 50 cycles, which demonstrates relatively promising cycling stability. Following electrochemical galvanostatic/ potentiostatic charge/ discharge experiments, TiO2 electrodes were carefully removed from electrochemical cells and examined for magnesium insertion mechanism. Following a careful transfer step to mitigate any exposure to oxygen, the TiO2 electrodes were examined using scanning electron microscopy (Phillips XL30) with an equipped energy dispersive X-ray detector (EDX), synchrotron X-ray diffraction, and ultraviolet-visible spectroscopy. Both the spectroscopic and microscopic characterization confirm that a Mg:Ti ratio of ~0.1:1 is able to reversibly shuttle between the working and counter electrodes in this battery system. Acknowledgement The authors acknowledge the support by the seed funding from Sustainable Power and Energy Center under the Frontier of Innovation Award by Vice Chancellor of Research at UC San Diego. References (1) Whittingham, M. S. Chem. Rev. 2004, 104, 4271 – 4301. (2) Muldoon, J.; Bucur, C. B.; Gregory, T. Chem. Rev. 2014, 114, 11683 – 11720. (3) Dahbi, M.; Yabuuchi, N.; Kubota, K.; Tokiwa, K.; Komaba, S. Phys. Chem. Chem. Phys. 2014, 16, 15007 – 15028. (4) Aurbach, D.; Weissman, I.; Goffer, Y.; Levi, E. Chem. Record 2003, 3, 61 – 73. Figure 1

Growth of Barrier Type Anodic Film on Magnesium in Ethylene Glycol-Water Mixed Electrolytes Containing Fluoride and Phosphate

In this study, we report the formation of barrier-type anodic films on magnetron-sputtered magnesium films at a constant current density of 10 A m−2 in ethylene glycol (EG)-H2O electrolytes containing 0.1 mol dm−3 ammonium fluoride and 0.1 mol dm−3 dipotassium hydrogen phosphate. The growth efficiency is close to 100% up to 10 vol% H2O, but decreases to 52% in the EG-free aqueous electrolyte. Even at such a low efficiency in the aqueous electrolyte a uniform barrier-type anodic film with flat and parallel metal/film and film/electrolyte interfaces is developed over 100 V. This is contrast to the non-uniform film growth and low breakdown voltage in the phosphate-free aqueous electrolyte containing ammonium fluoride. The anodic films appear to be amorphous regardless of H2O concentration in the phosphate-containing electrolytes, and consist of phosphate-incorporated oxyfluoride. The phosphate incorporation is suppressed by an increase in H2O concentration. In addition, the anodic films consist of two layers with an inner layer containing less amount of phosphate. The outer layer is probably formed at the film/electrolyte interface by the migration of Mg2+ ions outwards, while the inner layer is formed at the metal/film interface. The film formation at the former interface even in the aqueous electrolyte at low efficiency is likely to contribute to the formation of barrier films, not porous anodic films.

Comparative study of structural and visible luminescence properties of AZO thin film deposited on GaAs and porous GaAs substrates

The objective of this study is to investigate the effect of the pre-treatment of GaAs substrate by making it porous on structural and visible luminescence properties of aluminum - doped zinc oxide (AZO) thin films deposited by the use of a radio frequency magnetron sputtering. Porous GaAs has been prepared by anodic etching of n+-type (100) GaAs wafers in a HF:C2H5OH:HCl:H2O2:H2O electrolyte. Structural and visible luminescence properties of deposited films have been investigated by means of x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and room temperature photoluminescence (PL) spectroscopy. XRD patterns of deposited films show predominant orientation along (100) crystal plane of hexagonal ZnO. A diffraction peak due to cubic zinc arsenide (Zn3As2) is only observed in the XRD pattern of the film deposited on porous GaAs. XPS results further confirm that the AZO film deposited on porous GaAs is doped with arsenic (As). This is attributed to the enhancement of As diffusion into the film due to nanostructure nature of porous GaAs. The use of porous GaAs as a substrate also leads to an enhancement of the visible PL intensity of the deposited film. This is found to have a strong relationship with the change in the content of zinc and oxygen related defects in the film as it is revealed from peak analysis of XPS and PL spectra.

Ability of the Ion-Selective Electrode in the Thermodynamic Modeling of the Mixed Electrolyte System: The Case of the Ternary NH4Cl + KCl + H2O Mixed Electrolyte Systems

With the recent development and apparition of new sensors and selective membranes, ion-selective electrodes (ISEs) have become an attractive alternative method to the more usual vapor pressure or solvent activity methods for the investigation of thermodynamic properties of electrolyte systems. In this context, it seemed interesting to explore the ability of the ion-selective electrode in the thermodynamic modeling of mixed electrolyte systems. For this purpose, the mixed 1:1 electrolyte system with a common anion, namely the ternary NH4Cl + KCl + H2O electrolyte system was selected, in which the corresponding NH4+ and K+ cations are considered mutually as severe interfering ions for K+ ISE and NH4+ ISEs, respectively. In addition, Pitzer ion-interaction theory for mixed salts was applied for modeling the behavior of ternary electrolyte systems in concentrations ranging from 0.01 mol/kg up to 5 mol/kg, at 298.15 K. The reported results show, effectively, how the magnitude of the potentiometric selectivity coefficient (K12pot) of these ISEs, could play as limiting factors on the investigation of these systems.

Electrochemical behavior of nanostructured SnO2 thin films in aqueous electrolyte solutions

Novel nanostructures of tin oxide (SnO2) nanopyramids and nanoplates were grown on anodized Cu substrates using an electrodeposition method by altering deposition voltage. The chemical bonding, structure and morphology of nanostructures were examined using Fourier transform infrared spectra (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) and Field emission scanning electron microscope (FE-SEM). The orthorhombic crystal structure of electrodeposited SnO2 nanostructures has been confirmed by XRD. Microstructure from FE-SEM evidenced the existence of nanopyramids with edge length between 200 and 250nm and nanoplates of thickness 800nm. Cyclic voltammetric (CV) studies elaborate the electrochemical performance of prepared electrodes in aqueous LiOH·H2O, Li2CO3 and Li2SO4 electrolytes. Lithium ion alloying/de-alloying took place in all the above electrolytes for SnO2 electrodes confirmed by the appearance of pair of redox peaks at −0.35/−0.53V and 0.01/−0.45V (versus Ag/AgCl). CV curves of SnO2 electrodes in these aqueous solutions suggested battery characteristics of the material.

Characterization of hydrophobic, oxidized porous silicon layer formed by anodic etching of n+-type silicon surface in a HF:C2H5OH:HCl:H2O2:H2O electrolyte for bio-application

Porous silicon (PS) has been prepared in the dark by anodic etching of n+-type (111) silicon substrate in a HF:HCl:C2H5OH:H2O2:H2O electrolyte. The processed PS layer is characterized by means of photoluminescence (PL) spectroscopy, scanning electron microscope (SEM), water contact angle (CA) measurements, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and micro-Raman scattering. The CA of fresh PS layer is found to be ~142°. On aging at ambient conditions, the CA decreases gently to reach ~133° after 3 month, and then it is stabilized for a prolonged time of aging. The visible PL emission from the PS layer also exhibits a good stability against aging time. The FTIR and XPS measurements and analysis show that the stable aged PS layer has rather SiO2-rich surface. The micro/nanostructure nature of the PS layer is revealed from SEM and micro-Raman results and correlated to CA results. Stable hydrophobic surface of oxidized PS layer is attractive for bio-applications. The efficiency of the produced PS layers as an entrapping template for specific immobilization of IgG2a antibody via physical absorption process is demonstrated.

Preparation and luminescence properties of Tb3+ doped SiO2 film on TiO2 nanotube arrays

TiO2 nanotube arrays (TiO2 NTs) are fabricated by anodic oxidation of titanium in NH4Cl+H2O and NH4F+HOCH2CH2OH electrolytes respectively, then TiO2 NTs coated with Tb3+ doped SiO2 films (Tb–SiO2/TiO2 NTs) are prepared by sol–gel method and dip-coating process. The luminescence properties of Tb–SiO2/TiO2 NTs are investigated by fluorescence spectrometer. Results show that TiO2 NTs can improve the luminescence properties of Tb–SiO2, especially the TiO2 NTs fabricated in NH4Cl+H2O electrolyte. The emission intensity of Tb–SiO2 on the TiO2 NTs fabricated in NH4Cl+H2O electrolyte is five times to that on the pure titanium sheet. Additionally, the effect of TiO2 NTs preparation conditions on the Tb–SiO2 luminescence properties is analyzed in detail, and the luminescence enhancement mechanism of Tb–SiO2 on TiO2 NTs is explained.

Novel optical and structural properties of porous GaAs formed by anodic etching of n+-GaAs in a HF:C2H5OH:HCl:H2O2:H2O electrolyte: effect of etching time

Porous GaAs layers have been formed by anodic etching of n +-type GaAs (10.0) substrates in a HF:C2H5OH:HCl:H2O2:H2O electrolyte. A dramatic impact of etching time on the optical and structural properties of porous GaAs layer is demonstrated. The nano/micro-features of porous GaAs layers are revealed by scanning electron microscopy (SEM) imaging. Two-peak room temperature photoluminescence (PL), “blue-green” and “green-yellow”, is obtained in all prepared porous GaAs samples. Proper adjustment of etching time is found to produce a white color layer, instead of the usual dark gray color of porous GaAs. This is found to cause vast enhancement in the intensity of the visible PL in porous GaAs layer. Chemical composition and structural characterization by means of X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and micro-Raman spectroscopy, confirm that this layer is characterized with monoclinic β-Ga2O3 rich surface. Etching time induced—modification of structural and chemical properties of porous GaAs layer is discussed and correlated to its PL behavior. It is inferred that the “blue-green” PL in porous GaAs can be ascribed to different degrees of quantum confinement in GaAs nanocrystallites, whereas, the “green-yellow” PL is highly influenced by the As2O3 and Ga2O3, content in the porous GaAs layer. In addition, the reflectance measurements reveal an anti-refection trend of behavior of porous GaAs layers in the spectral range (500–1,100 nm).

In-situ synchrotron energy-dispersive x-ray diffraction study of thin Pd foils with Pd:D and Pd:H concentrations up to 1:1

Time resolved, in-situ, energy dispersive x-ray diffraction was performed in an electrolysis cell during electrochemical loading of palladium foil cathodes with hydrogen and deuterium. Concentrations of H:Pd (D:Pd) up to 1:1 in 0.1 M LiOH (LiOD) in H2O (D2O) electrolyte were obtained, as determined by both the Pd lattice parameter and cathode resistivity. In addition, some indications on the kinetics of loading and deloading of hydrogen from the Pd surface were obtained. The alpha-beta phase transformations were clearly delineated but no new phases at high concentration were determined.

A facile route to accelerate the formation of TiO2 nanotube arrays

Highly ordered TiO2 nanotube arrays fabricated by electrochemical anodization of titanium have attracted significant attention due to their splendid promising applications. One of the factors limiting the application of TiO2 nanotube arrays was their long sustaining reaction time by anodic oxidation, usually lasting 6 – 12 h and even longer when systhesizing thicker nanotubular layers. In this paper, we reported for the first time a facile and effective route to accelerate the formation of TiO2 nanotube arrays by proper proportional addition of sodium carbonate(Na2CO3) into the anodization electrolyte. In our experiments, we adopted the 0.3 wt% NH4F + EG (ethylene glycol) + 3.0 vol% H2O electrolyte and we added Na2CO3 with the proportion n(NH4F) : n(Na2CO3) = 1:1, 2:1, 3:1, 4:1 and 5:1. The field-emission scanning electron microscope (FESEM) characterization results suggested the Na2CO3 additives accelerated the growth rate of the TiO2 nanotubes with the quickest growth rate 1100 nm/min when n(NH4F) : n(Na2CO3) = 2:1. Finally, we investigated the mechanism of the Na2CO3 additives accelerating the growth rate of the TiO2 nanotubes. It was believed that the hydrolyzation of the Na2CO3 additives in the electrolytes accelerated the formation of the TiO2 nanotubes and at the same time restrained the chemical dissolution of the formed TiO2 nanotubes.

Structure and dynamics of phospholipid bilayer films under electrochemical control

Vesicle fusion was used to deposit mixed dimyristoyl phosphatidylethanolamine–dimyristoyl phosphatidylserine (DMPE–DMPS) phospholipid bilayers on Au electrodes. Bilayer structure and composition, when exposed to aqueous NaF and subject to an applied electrochemical potential, were studied using electrochemical, spectroscopic and neutron reflectivity (NR) techniques. Interfacial capacitance data indicate the formation of compact films. Chronocolometric data show that surface charge is significantly altered by the presence of lipid in the potential range −0.75 < E/V (Ag|AgCl) < 0.35. NR measurements were made on lipid films in which the hydrocarbon tails were either fully hydrogenous (h-DMPE–h-DMPS) or perdeuterated (d-DMPE–d-DMPS), in each case serially exposed to D2O and H2O electrolytes and subject to different applied potentials. Guided by simulations of candidate interfacial structures, these yield the spatial distributions of lipid and solvent within the layers. Adjacent to the electrode, a compact inner leaflet is formed, with potential-dependent solvent volume fraction in the range 0.09 < ϕS < 0.19; there was no evidence of an intervening water layer. The outer leaflet contains rather more solvent, 0.52 < ϕS < 0.55. NR-derived film thickness and PM-IRRAS intensity data show that the lipid molecules are tilted from the surface normal by ca. 26°. Bilayer solvation and charge data show a strong correlation for the inner leaflet and very little for the outer leaflet.

Preparation of short, robust and highly ordered TiO2 nanotube arrays and their applications as electrode

The short, robust and highly ordered TiO2 nanotube arrays (TNAs) electrode was prepared by sonoelectrochemical anodization of titanium in HF–H2O electrolyte solution (referred as short TNAs, STNAs). The self-organized arrays of titania nanotubes of approximately 12–65nm in diameter and 75–280nm in length can be synthesized at anodic voltage of 5–20V. The electron transport process within the STNAs electrode was much favorable in comparison with that for the long TNAs electrode synthesized by conventional magnetic agitation technique (referred as long TNAs, LTNAs), as confirmed by the obviously enhanced photocurrent response of STNAs electrode either in 0.02M Na2SO4 electrolyte solution or in different concentrations of glucose solution or under different intensities of UV illumination. To investigate their photoelectrochemical applications, degradation of tetracycline, a typical pharmaceutical and personal care products (PPCPs), was carried out using photoelectrocatalytic (PEC) means, comparing with electrochemical (EC) and photocatalytic (PC) processes. The kinetic constant of the PEC process of STNAs electrode was ∼3.17 times as high as its PC process. The color removal rate of tetracycline by STNAs electrode achieved 81% within 3h, which was 21% higher than that for LTNAs electrode. In degrading tetracycline, 41% of TOC was mineralized using the STNAs electrode against 23% using LTNAs electrode under similar conditions. Such kind of titania nanotubes will have many potential applications in various areas as an outstanding photoelectrochemical material.

Modeling of the Mixed Solvent Electrolyte System CO2−Na2CO3−NaHCO3−Monoethylene Glycol−Water

The extended UNIQUAC electrolyte activity coefficient model has been correlated to 751 experimental solid−liquid equilibrium (SLE), vapor−liquid equilibrium (VLE), and excess enthalpy data for the mixed solvent CO2−NaHCO3−Na2CO3−monoethylene glycol(MEG)−H2O electrolyte system. The model was validated by predicting the excess heat capacity. The model is consistent, and one set of binary interaction parameters are used for calculating all the properties between −50 and 90 °C. The model is compared to experimental data of infinite dilution activity coefficient measurements of MEG and may be used for calculating activities, solubility, salt hydrate properties, pH, and CO2 solubility in the NaHCO3−Na2CO3−MEG−H2O system. A simple density model of NaHCO3−Na2CO3−NaCl−MEG−water is given.

The Role of Ce Ions in Electrochemical Corrosion of 304 SS in Ce(NO3)3.6H2O

Effects of temperature and potential on the electrochemical corrosion behavior of alloy AISI 304 (UNS S30400) Stainless steel were investigated in 3 wt.% cerium nitrate (Ce[NO3]3.6H2O) solution. With an increase in electrolyte temperature from ambient temperature to 90°C, the corrosion potential of the alloy shifted towards the noble direction, and the resistance to polarization increased due to the formation of Ce-oxide on the electrode surface. The oxide films formed at the open circuit potential (OCP) and a passive potential of 0.4 VSCE were examined by x-ray photoelectron spectroscopy (XPS). The oxide film formed at 50°C and a passive potentialof 0.4 VSCE consists of mixed oxides of Ce and Cr, whereas that at OCP consists of only Cr oxide. The formation of Cr oxides on the electrode surface was primarily due to the nitrate (NO3 −) ions in Ce(NO3)3.6H2O electrolyte.

TERNARY NaCl+LiCl+H2O MIXED ELECTROLYTE SYSTEM: DETERMINATION OF ACTIVITY COEFFICIENTS BASED ON POTENTIOMETRIC METHOD

The mean activity coefficients for NaCl in a ternary electrolyte system were determined by the potentiometric method, at 25°C, using a solvent polymeric (PVC) sodium-selective membrane electrode (Na+ ISE), containing N,N′-dibenzyl-N,N′-diphenyl-1,2-phenylenedioxydiacetamide as ionophore, and combined with an Ag/AgCl electrode. The potentiometric measurements were performed at the same ionic strengths in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r (where r = m1/m2 = 1, 10, 50, 100). The nonideal behavior of the ternary NaCl(m1) + LiCl(m2) + H2O electrolyte system was described based on the Pitzer ion-interaction model for mixed salts over the ionic strength ranging from 0.01 up to about 4 mol/kg. Two- and three-particle Pitzer interaction parameters for a mixed electrolyte system were determined based on potentiometric data, and the critical role of potentiometric selectivity coefficient (K 12) of ISE as limiting factor in the potentiometric measurements was analyzed.

Bartter syndrome and cholelithiasis in an infant: is this a mere coincidence?

The case of an infant with both Bartter syndrome and cholelithiasis is presented. We felt that this association of two rare diseases might not be coincidental, thus prompting us to publish this report. Typically, patients affected with Bartter exhibit marked urinary excretion of electrolytes associated with polyuria and, consequently, are prone to develop dehydration [5]. On the other hand, cholelithiasis is a rarely reported condition in infants [4], and several predisposing factors for this condition have been identified such as prematurity, prolonged fasting, parenteral nutrition, use of furosemide, sepsis and dehydration to name a few [3]. This male Caucasian infant was born after 38 weeks of gestation. Presence of severe polyhydramnios had first been noted at 32 weeks of pregnancy. Physical examination of the infant at birth was entirely normal. His serum electrolytes and creatinine were normal during the first two days. Renal ultrasound examination was also unremarkable. On day four it was observed that he had become polyuric and the typical serum electrolyte profile of Bartter had developed. (Serum sodium 135 mmol/L, potassium 2.8 mmol/L, bicarbonate 28.5 mmol/L and chloride 93 mmol/L). Serum creatinine was normal at 32 μmol/L, as well as serum magnesium at 0.83 mmol/L whereas serum calcium was slightly elevated at 2.82 mmol/L. Urinary osmolality remained low at approximately 130–140 mOsm/Kg H2O and urinary electrolyte concentrations done on several samples averaged 30 mm/L for sodium, 20 mm/L for potassium and 40 mm/L for chloride. At the same time, plasma renin activity was extremely elevated at 123 ng/ml per hour (normal 7.1 to 23.8) and plasma aldosterone 954 ng/dl (normal 30 to 201). At six months he was admitted for fever, vomiting and passage of discoloured stools. Presence of a gallbladder stone was clearly visible on ultrasound examination (Fig. 1). Fortunately, the child was able to evacuate his gallstone spontaneously. Presence of risk factors for cholelithiasis such as hemolytic disease and hyperlipidemia were not present. In addition, it is noteworthy that the infant had not been administered third generation cephalosporins and he was not fed by hyperalimention nor in a prolonged fasting state. Fig. 1 Ultrasound examination showing presence of a 4 mm cholelithiasis in the gallbladder neck On follow-up, he proved to be very difficult to manage, requiring enormous electrolyte supplementation in addition to indomethacin and aldactone administration. An adequate state of hydration was obtained through tube feeding by a gastro-jejunostomy. Upon transfer to another medical center in a different city at age 22 months, he was extremely growth retarded at 78 cm (below the third percentile). Bartter syndrome and cholelithiasis in infants are both very rare diseases. An association between these two conditions was sought by retrospectively examining abdominal ultrasounds available in six of our patients with Bartter syndrome but no gallstones were found. The association of these two conditions has never been published before. However, we asked families of patients with Bartter syndrome if they were aware of the simultaneous occurrence of these two diseases on a web site where patients affected with Bartter can exchange information (http://www.health.groups.yahoo.com/group/barttersyndrome/message). Surprisingly, several patients with Bartter replied having had cholelithiasis at a young age. Most striking was the case of a female baby born at term with the neonatal variant of Bartter syndrome, where the diagnosis of cholelithiasis was made at three months of age. This suggested that the association is most probably more frequent than it would be expected if there were no connections between the two conditions. In fact, infants with Bartter typically present with metabolic alkalosis, dehydration and urinary electrolyte losses. It is well established that serum and bile bicarbonate levels are in equilibrium and that alkalinization of bile favours precipitation of calcium carbonate, a key constituent of gallstones [2]. Conversely, systemic acidification induced by acetazolamide has the potential to prevent cholelithiasis formation [6]. Furthermore, dehydration which increases bile viscosity and electrolyte urinary losses such as occurs in pseudohypo-aldosteronism [1] may also promote gallstone formation. Thus factors predisposing to gallstone formation are present in patients with Bartter syndrome and routine ultrasonic screening for gallstones should be performed in these patients who often present bouts of vomiting without obvious explanations.