Determination of water activities, osmotic and activity coefficients in aqueous solutions using the hygrometric method

Guendouzi, Mohamed El; Dinane, Abderrahim

doi:10.1006/jcht.1999.0574

Cited by 85 publications

(84 citation statements)

References 26 publications

(24 reference statements)

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“…Moreover, this suggests that films formed in the presence of Na 2 SO 4 are more stable than those in the presence of Cl − which could be related to 0.1 M Na 2 SO 4 having an SO 4 2− activity coefficient < 1. 60 A low anion activity coefficient would lead to a less reactive environment, which decreases the likelihood of dissolution film breakdown during anodic polarization. In addition, it was more difficult to mechanically remove the Na 2 SO 4 films when removing surface films for ICP-OES analysis compared to Cl − solutions films.…”

Section: Discussionmentioning

confidence: 99%

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

Cain

Gonzalez-Afanador

Birbilis

et al. 2017

J. Electrochem. Soc.

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The anodic dissolution and associated hydrogen evolution of high purity Mg (80 ppmw Fe) was studied as a function of potential in unbuffered 0.6 M NaCl (pH ≈ 8.5), 0.6 M NaCl saturated with Mg(OH) 2 (pH ≈ 10.25), 0.1 M MgCl 2 (pH ≈ 5.6), 0.1 M Na 2 SO 4 (pH ≈ 5.5), and a 0.1 M Tris(hydroxymethyl)aminomethane hydrochloride (TRIS, pH ≈ 7.25) buffer solution via simultaneous mass loss, hydrogen volume collection, potentiostatic and potentiodynamic polarization, and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The negative difference effect (NDE) was substantial in the unbuffered Cl − containing environments where Mg(OH) 2 formed on the surface and weak in 0.1 M Na 2 SO 4 . In contrast, the 0.1 TRIS buffered solution exhibited a positive difference effect and the absence of thick corrosion films. Mg(OH) 2 films formed on samples in Cl − spalled off easily whilst the Mg(OH) 2 films formed in 0.1 M Na 2 SO 4 were more tenacious, which suggests that film stability plays significant role in the NDE. Research and development of magnesium (Mg) and its alloys has greatly increased in the last 15 years primarily due to the demand for lightweight vehicles in the automotive and aerospace industries, 1 in addition to the exploration of Mg as an anode material in primary and secondary batteries.2 However, the poor corrosion resistance and complex dissolution behavior of Mg has limited its wider use as an engineering material.3-5 One aspect associated with Mg dissolution which has not to date been mechanistically elucidated in full, is the phenomenon known as the negative difference effect (NDE).3 This effect is characterized by an increase in the rate of hydrogen evolution with increasing anodic overpotential relative to the open circuit -which provides a local cathodic reaction for a significant portion of the anodic reaction.6 This phenomenon confounds the understanding of Mg dissolution mechanisms, establishment of a Tafel law and other reaction kinetic parameters, as well as other issues including accurate analysis of corrosion rates from electrochemical impedance spectroscopy (EIS). [7][8][9] There are several theories purporting to explain the origins of the NDE among which include noble impurity element enrichment, 10,11 non-faradaic mass loss via metal spalling, 12,13 formation and dissolution of hydrides and partially protective films, [14][15][16][17] and univalent Mg based dissolution followed by further oxidation of Mg + →Mg 2+ in solution (leading to hydrogen evolution from the reduction of water away from the electrode in the electrolyte);18 however, no consensus has been reached on the physical origins of the NDE.The contemporary paradigm for the manifestation of the NDE centers on evidence for the enhanced cathodic activity of dissolving Mg anodes;19 whereby numerous works confined within a relatively recent timeframe have elucidated such a phenomenon. Evidence of enhanced cathodic activity has been reported by Williams and coworkers through use of the scanning vibrating electrode techniqu...

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Section: Discussionmentioning

confidence: 99%

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

Cain

Gonzalez-Afanador

Birbilis

et al. 2017

J. Electrochem. Soc.

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“…The deliquescence point is for KCl ∼ 0.84 (Tang 1997), and the measured deliquescence point for K 2 CO 3 is between 0.30-0.40 (when estimated from solubility: 0.54). For K 2 SO 4 , water activity data from Guendouzi et al (2003) were used. However, they only measured the water activity for non-supersaturated (bulk) solutions.…”

Section: Water Activities Of the Pure Saltsmentioning

confidence: 99%

“…As a result of the variable degree of dissociation and non-ideal interactions in the electrolyte, the van't Hoff factor varies with molality. In the interval measured by Guendouzi et al (2003) (a w = 0.972-0.9958), a van't Hoff factor of 2.05 can describe the measured water activity. This value was inserted into Köhler theory to extrapolate the hygroscopic behavior of K 2 SO 4 down to supersaturated solutions.…”

Section: Water Activities Of the Pure Saltsmentioning

confidence: 99%

Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

Rissler

Pagels

Swietlicki

et al. 2005

Aerosol Science and Technology

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This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf ) was measured when taken from a dehydrated to a humidified state for particle diameters between 30-350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1 MW boiler, and 1.5 in the 1.5 MW boiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K 2 SO 4 , and K 2 CO 3 ). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractallike structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ∼2.5.

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“…In a previous paper (1) we described a measurement technique based on the hygrometric method and presented experimental results. We have now extended the measurements using this method to cover the following salts: HCl(aq), LiCl(aq), NaCl(aq), KCl(aq), CsCl(aq), NH 4 Cl(aq), MgCl 2 (aq), CaCl 2 (aq), and BaCl 2 (aq).…”

Section: Introductionmentioning

confidence: 98%

Water activities, osmotic and activity coefficients in aqueous chloride solutions atT= 298.15 K by the hygrometric method

Guendouzi

Dinane

Mounir

2001

The Journal of Chemical Thermodynamics

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Determination of water activities, osmotic and activity coefficients in aqueous solutions using the hygrometric method

Cited by 85 publications

References 26 publications

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

Water activities, osmotic and activity coefficients in aqueous chloride solutions atT= 298.15 K by the hygrometric method

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Determination of water activities, osmotic and activity coefficients in aqueous solutions using the hygrometric method

Cited by 85 publications

References 26 publications

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl−versus Cl−Free Solutions

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl−versus Cl−Free Solutions

Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

Water activities, osmotic and activity coefficients in aqueous chloride solutions atT= 298.15 K by the hygrometric method

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The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions