scholarly journals The kinetic theory of surface films. Part I.—The surfaces of solutions

1925 ◽  
Vol 109 (749) ◽  
pp. 57-77 ◽  
Keyword(s):  
Surface Tension ◽  
Phase Boundary ◽  
Pure Water ◽  
Molar Fraction ◽  
Single Layer ◽  
Hydrocarbon Chain ◽  
Homogeneous Layer ◽  
Cooh Group ◽  
Surface Films ◽  
Small Molecular Weight

A study of the catalytic properties of solid surfaces has led to a belief that the distance at which molecules cease to attract one another appreciably is of the same order of magnitude as the diameter of an atom, a distance much smaller than that imagined by Laplace. On the Laplacian view the transition between liquid and vapour at a phase-boundary is gradual, but on the newer theory the non-homogeneous layer separating the homogeneous phases is little, if at all, greater than the diameter of a molecule. The work of Langmuir (1) on the influence of small quantities of certain insoluble organic substances upon the surface tension of water supports the latter view. The substances which are found to act in this way are hydrocarbons in which has been substituted an “ active ” group, such as COOH or OH. These groups tend to make the substance soluble in water, but the substitution of only one of them in a hydrocarbon containing more than twelve carbon atoms in the molecule is insufficient to cause any appreciable solution. Langmuir suggests that molecules of, say, palmitic acid placed on water orientate themselves, so that the COOH group is in the liquid phase while the hydrocarbon chain is in the vapour phase, a condition which is only realizable if the phase boundary is relatively sharp. His well-known trough experiments (2) amply support this idea, and confirm the necessary corollary : that a water surface of a given area can only accommodate a limited number of orientated molecules. N. K. Adam (3), in repeating and extending Langmuir’s experiments with more refined apparatus, has shown that the least area occupied by these molecules is in excellent agreement with that to be expected from the recent X-ray determinations of Sir William Bragg. In the paper in which his work on insoluble films is described Langmuir also deals with the lowering of the surface tension of water by soluble substances (4), such as the fatty acids and alcohols of small molecular weight. He suggests that the excess concentration of solute, which an application of Gibbs’ adsorption equation shows to exist in the neighbourhood of the phase boundary, is present as a single layer of molecules, orientated partially or completely like those of insoluble substances. In support of this he quotes a paper by Milner (5), where it is shown that soluble substances which depress the surface tension of water appear to give a surface excess reaching a constant limiting value for large depressions. This conclusion is drawn from the fact that the relation σ 0 — σ = α + β log 10 N (i) is found to represent the behaviour of solutions of acetic acid for large values of σ 0 — σ. In this equation σ is the surface tension of the solution, while σ 0 is that of pure water ; N is the molar fraction of the solute, and α and β are constants.

scholarly journals The behaviour of crystals and lenses of fats on the surface of water.—Part II. The effect of temperature on the equilibrium pressure

1925 ◽  
Vol 109 (750) ◽  
pp. 318-330 ◽  
Keyword(s):  
Surface Tension ◽  
Pure Water ◽  
Hydrocarbon Chain ◽  
Effect Of Temperature ◽  
Two Dimensional ◽  
Equilibrium Pressure ◽  
Equilibrium Surface Tension ◽  
Rate Of Spread ◽  
Definite Interval ◽  
Increasing Temperature

In Part I a study was made of the rate of spread and unimolecular nature of films of fatty substances, containing a long hydrocarbon chain and a polar “head,” over a surface of pure water or of N/100 HC1. It was shown that after a definite interval of time, the surface became saturated with a unimolecular film in equilibrium with either a crystal or a lens of the substance in question, and that the time taken to attain equilibrium as well as the equilibrium surface tension was a function of the temperature. In the present paper the effect of increasing temperature on the two-dimensional equilibrium pressure is considered in detail.

Discussion on Grosenbaugh and Yeung: “Flow Structure Near the Bow of a Two-Dimensional Body”

1990 ◽  
Vol 34 (03) ◽  
pp. 206-206
Author(s):  
G. E. Gadd
Keyword(s):  
Surface Tension ◽  
Surface Film ◽  
Pure Water ◽  
Marangoni Effect ◽  
Surface Region ◽  
Surface Flow ◽  
Surface Films ◽  
Soap Bubble ◽  
Two Dimensional ◽  
Reduce Surface Tension

A note on surface tension effects on breaking bow waves - In their interesting recent paper [1], Grosenbaugh and Yeung show that the forward extent of a breaking bow wave in front of a two-dimensional body can be significantly affected by the addition of surfactants to reduce surface tension. However, although they note that contaminants such as dust can also affect the surface flow, they appear to be unaware of the possibility that dynamic effects on surface tension, particularly when surfactants are present, may play an important role, as discussed in reference [2]. As shown by Davies [3], surface films can damp eddies at a free surface of a turbulent liquid. The mechanism is due to the so-called Marangoni effect; that is, where a surface film is locally stretched, the surface contaminant concentration is momentarily reduced, leading to an increase in surface tension which tends to contract the local surface region again. This is why a soap bubble is so much more stable than one formed in pure water. Similarly, upwelling flows associated with turbulence at a water surface cause local stretching and contraction which will tend to be opposed by the presence of the surface contaminant.

Experimental and Numerical Study of Methanol-Water Mixture Single-Phase Heat Transfer in a Micro-Channel Heat Sink

2012 ◽  
Author(s):  
Chun K. Kwok ◽  
Matthew M. Asada ◽  
Jonathan R. Mita ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Single Phase ◽  
Numerical Study ◽  
Pure Water ◽  
Molar Fraction ◽  
Water Mixture ◽  
Micro Channel ◽  
Numerical Predictions

This paper presents an experimental study of single-phase heat transfer characteristics of binary methanol-water mixtures in a micro-channel heat sink containing an array of 22 microchannels with 240μm × 630μm cross-section. Pure water, pure methanol, and five methanol-water mixtures with methanol molar fraction of 16%, 36%, 50%, 63% and 82% were tested. Key parametric trends were identified and discussed. The experimental study was complemented by a three-dimensional numerical simulation. Numerical predictions and experimental data are in good agreement with a mean absolute error (MAE) of 0.87%.

scholarly journals On the contribution of Aitken mode particles to cloud droplet populations at continental background areas – a parametric sensitivity study

2007 ◽  
Vol 7 (3) ◽  
pp. 6077-6112
Author(s):  
T. Anttila ◽  
V.-M. Kerminen
Keyword(s):  
Surface Tension ◽  
Particle Size ◽  
Chemical Composition ◽  
Pure Water ◽  
Particle Surface ◽  
Chemical Properties ◽  
Sensitivity Study ◽  
Geometric Standard Deviation ◽  
Cloud Droplets ◽  
Aitken Mode

Abstract. Aitken mode particles are potentially an important source of cloud droplets in continental background areas. In order to find out which physico-chemical properties of Aitken mode particles are most important regarding their cloud-nucleating ability, we applied a global sensitivity method to an adiabatic air parcel model simulating the number of cloud droplets formed on Aitken mode particles, CD2. The technique propagates uncertainties in the parameters describing the properties of Aitken mode to CD2. The results show that if the Aitken mode particles do not contain molecules that are able to reduce the particle surface tension more than 30% and/or decrease the mass accommodation coefficient of water, α, below 10−2, the chemical composition and modal properties may have roughly an equal importance at low updraft velocities characterized by maximum supersaturations <0.1%. For larger updraft velocities, however, the particle size distribution is clearly more important than the chemical composition. In general, CD2 exhibits largest sensitivity to the particle number concentration, followed by the particle size. Also the shape of the particle mode, characterized by the geometric standard deviation (GSD), can be as important as the mode mean size at low updraft velocities. Finally, the performed sensitivity analysis revealed also that the chemistry may dominate the total sensitivity of CD2 to the considered parameters if: 1) the value of α varies at least one order of magnitude more than what is expected for pure water surfaces (10−2–1), or 2) the particle surface tension varies more than roughly 30% under conditions close to reaching supersaturation.

scholarly journals Aerosol hygroscopicity at high (99 to 100%) relative humidities

2009 ◽  
Vol 9 (4) ◽  
pp. 15595-15640 ◽  
Author(s):  
C. R. Ruehl ◽  
P. Y. Chuang ◽  
A. Nenes
Keyword(s):  
Surface Tension ◽  
Inorganic Compounds ◽  
Droplet Diameter ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Bulk Solution ◽  
Active Compounds ◽  
Surface Active ◽  
Surface Active Compounds ◽  
Aerosol Hygroscopicity

Abstract. The hygroscopicity of an aerosol largely determines its influence on climate and, for smaller particles, atmospheric lifetime. While much aerosol hygroscopicity data is available at lower relative humidities (RH) and under cloud formation conditions (RH>100%), relatively little data is available at high RH (99.2 to 99.9%). We measured the size of droplets at high RH that had formed on particles composed of one of seven compounds with dry diameters between 0.1 and 0.5 μm, and calculated the hygroscopicity of these compounds. We use a parameterization of the Kelvin term, in addition to a standard parameterization (κ) of the Raoult term, to express the hygroscopicity of surface-active compounds. For inorganic compounds, hygroscopicity could reliably be predicted using water activity data and assuming a surface tension of pure water. In contrast, most organics exhibited a slight to mild increase in hygroscopicity with droplet diameter. This trend was strongest for sodium dodecyl sulfate (SDS), the most surface-active compound studied. The results suggest that partitioning of surface-active compounds away from the bulk solution, which reduces hygroscopicity, dominates any increases in hygroscopicity due to reduced surface tension. This is opposite to what is typically assumed for soluble surfactants. Furthermore, we saw no evidence that micellization limits SDS activity in micron-sized solution droplets, as observed in macroscopic solutions. These results suggest that while the high-RH hygroscopicity of inorganic compounds can be reliably predicted using readily available data, surface-activity parameters obtained from macroscopic solutions with organic solutes may be inappropriate for calculations of the hygroscopicity of micron-sized droplets.

scholarly journals Tribological Properties of Si3N4-hBN Composite Ceramics Bearing on GCr15 under Seawater Lubrication

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 635 ◽  
Author(s):  
Fang Han ◽  
Huaixing Wen ◽  
Jianjian Sun ◽  
Wei Wang ◽  
Yalong Fan ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Tribological Properties ◽  
Photoelectron Spectroscopy ◽  
Dry Friction ◽  
Pure Water ◽  
Water Environment ◽  
Surface Films ◽  
Seawater Lubrication ◽  
Pin On Disc ◽  
Worn Surface

This paper concerns a comparative study on the tribological properties of Si3N4-10 vol% hBN bearing on GCr15 steel under seawater lubrication and dry friction and fresh-water lubrication by using a pin-on-disc tribometer. The results showed that the lower friction coefficient (around 0.03) and wear rate (10−6 mm/Nm) of SN10/GCr15 tribopair were obtained under seawater condition. This might be caused by the comprehensive effects of hydrodynamics and boundary lubrication of surface films formed after the tribo-chemical reaction. Despite SN10/GCr15 tribopair having 0.07 friction coefficient in the pure-water environment, the wear mechanismsits were dominated by the adhesive wear and abrasive wear under the dry friction conditions, and delamination, plowing, and plastic deformation occured on the worn surface. The X-ray photoelectron spectroscopy analysis indicated that the products formed after tribo-chemaical reaction were Fe2O3, SiO2, and B2O3 and small amounts of salts from the seawater, and it was these deposits on the worn surface under seawater lubrication conditions that, served to lubricate and protect the wear surface.

scholarly journals An Experimental Study on Wetting of Coal Dust by Surfactant Solution

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yidan Jiang ◽  
Pengfei Wang ◽  
Ronghua Liu ◽  
Ye Pei ◽  
Gaogao Wu
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Reverse Osmosis ◽  
Sodium Sulfate ◽  
Moisture Absorption ◽  
Coal Dust ◽  
Pure Water ◽  
Surfactant Solution ◽  
Limited Range ◽  
Dust Reduction

Surfactants can improve the wetting performance of the dust-reduction spraying water, thus improving the dust-reduction effect by spray. In this study, the performance of surfactant solution in wetting coal dust was investigated through experiments. In addition, the effects of surfactant type, mass fraction, metamorphic degree of coal, particle size, and additives were investigated. According to the results of surface tension experiments, the surface tension of the solution decreased with the increase of the concentration of surfactant. However, after reaching CMC, the surface tension did not have significantly decrease. SDBS and OP-10 had higher efficiency in decreasing the surface tension than the other two types of surfactants. The addition of sodium sulfate additives can further reduce the surface tension of the surfactant solution by a limited range. The coal dust wetting experiment showed that with the increase in the concentration of the surfactant, the contact angle of the droplets on the coal dust tablet was continuously reduced, and the wettability of the solution was continuously improved. The wettability of the OP-10 solution was optimal. At the same concentration, the minimum contact angle can be obtained in the OP-10 solution. As the contact angle of the coal dust increased, the growth rate in the coal dust reverse osmosis moisture absorption of the surfactant solution relative to the pure water increased. After the addition of sodium sulfate, the reverse osmosis moisture absorption of coal dust increased to varying degrees. In addition, as the concentration of additives increased, the moisture absorption of coal dust increased.

scholarly journals Micellization Behavior of Cetyltrimethylammonium bromide in Presence and Absence of Na2SO4 and MgSO4 in Aqueous media

BIBECHANA ◽  
2016 ◽  
Vol 14 ◽  
pp. 77-85 ◽  
Author(s):  
Chom Nath Adhikari ◽  
G S Shrivastav ◽  
Ajaya Bhattarai
Keyword(s):  
Surface Tension ◽  
Critical Micelle Concentration ◽  
Cetyltrimethylammonium Bromide ◽  
Pure Water ◽  
Aqueous Media ◽  
Presence And Absence ◽  
Micellization Behavior

Viscosity and surface tension measurements of cetyltrimethylammonium bromide (CTAB) in presence and absence of Na2SO4 and MgSO4 in aqueous media are reported. The results showed an increase in viscosity with increase in concentration of cetyltrimethylammonium bromide in presence and absence of salts where as the decrease in surface tension with increase in concentration of cetyltrimethylammonium bromide in presence and absence of salts. The viscosity of CTAB was observed lowest in pure water and increases in presence of MgSO4 and then more increases in presence of Na2SO4 where as the surface tension of CTAB was observed highest in pure water and decreases in presence of Na2SO4 and then more decreases in presence of MgSO4.The critical micelle concentration (cmc) of CTAB decreases in presence of salts in both viscosity and surface tension measurements. The decreasing cmc of CTAB are found to be more in the presence of Na2SO4 in comparison with the presence of MgSO4 for both measurements. The graphs of viscosity versus log[C] and the surface tension versus log[C] are used in determining the critical micelle concentration (cmc).        BIBECHANA 14 (2017) 77-85

Experimental Investigation of Low Weber Number Post-Impact Drop Spreading on Solid Substrates

2010 ◽  
Author(s):  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Pure Water ◽  
Surfactant Solution ◽  
Video Camera ◽  
Dynamic Surface Tension ◽  
Temporal Variations ◽  
Dynamic Surface ◽  
Post Impact ◽  
Triton X

The post-impact spreading and recoil behaviors of droplets of pure liquids (water and ethanol) and aqueous solution of Triton X-100 (a surfactant) on a dry horizontal hydrophilic (glass) substrate are investigated for low Weber numbers. The evolution of drop shape during spreading and recoil are captured using a high-speed (4,000 frames per second) digital video camera. Digital image-processing was used to determine the spread and height of the liquid film on the surface from each frame. Unlike pure liquids, the liquid-gas interfacial tension for surfactant solution is a function of surface age, where surface tension is that of the solvent at zero time and then reaches an equilibrium value with increasing surface age. Furthermore, the equilibrium surface tension is a function of the surfactant concentration, which decreases from that of the solvent at zero concentration to that at the critical micelle concentration (CMC), and remains essentially constant thereafter. The surface tension of aqueous Triton X-100 solution varies from that of pure water to nearly that of ethanol. As such the comparison of transient droplet-impact-spreading-recoil behavior of the three liquids, or their temporal variations of the spread and the flattening factor, provides a basis for understanding the role of dynamic surface tension and surface wettability.

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