Decrease In Permeability Coefficient Research Articles

Effect of sticky rice on the strength and permeability of bio-cemented sand

Microbially induced carbonate precipitation (MICP) is an eco-friendly soil improvement technique. However, this method still has some drawbacks, such as low conversion efficiency of CaCO3 crystallization, insufficient strength for certain applications, and requiring multiple treatments. Previous studies have reported that sticky rice can regulate CaCO3 crystals (i.e., chemical CaCO3) in the sticky rice-lime mortar, showing potential for improving the bio-cementation. Therefore, this study explored the possibility of using sticky rice to enhance the biocementation effect. Tests were carried out to assess the strength and permeability of bio-cemented sand with the inclusion of sticky rice. The results indicated that sticky rice may regulate the type and size of bio-CaCO3 crystals, and the use of an appropriate amount of sticky rice as additive could increase the strength of sand columns by regulating CaCO3 crystallization. Polyhedral calcites may be more favourable for the increasing strength than some vaterites with a hollow spherical structure. The combination of MICP and sticky rice can significantly decrease the coefficient of permeability to a value that was much lower than that by using sticky rice and MICP alone. Bio-CaCO3 immobilized the sticky rice on one end on sand particles, and the reticulated structure of sticky rice divided large pores into small pores, which may be the important cause of the decrease in permeability coefficient. Finally, this study proposed that the MICP with the sticky rice as an additive may enhance the MICP effect and prevent the surface erosion of coarse-grained sand slopes.

Experimental study on the stabilization and anti-seepage treatment of lead and zinc elements in heavy metal tailings pond using cement slurry containing heavy metal stabilizing agent

The release of heavy metal elements in heavy metal tailings ponds not only causes environmental pollution but also poses potential hazards to human health. Therefore, it is of great significance to stabilize heavy metals and apply anti-seepage treatment to tailings ponds. In this paper, the tailings in the Shenxiandong lead-zinc tailings pond in Yunnan Province, Southwest China, were analyzed. The adsorption effects of different natural stabilizing agents on lead (Pb) and zinc (Zn) in tailings were investigated. Orthogonal and modification experiments were used to identify the most effective stabilizing agent. This agent was then combined with a high-pressure rotary jet cement slurry to investigate the properties of the resulting consolidation body and its effect on heavy metal solidification. The results show that the tailings are more likely to release heavy metal elements into the environment. The results of the orthogonal experiments show that the stabilizing agent CCA, which is a combination of fly ash, attapulgite, and Na-bentonite in a 2:1:2 ratio, effectively adsorbs Pb and Zn elements in the tailings. The stabilizing agent CCAPT is created by modifying CCA with 7% H3PO4 at pH of 12 and heat treating at 200 °C. CCAPT demonstrates a 97.2% improvement in stabilization efficiency for Pb and a 94.1% improvement for Zn compared to CCA. The combination of CCAPT and cement slurry resulted in a 25.6% increase in compressive strength and a 29.5% decrease in permeability coefficient compared to the cement slurry formed consolidation body. The core-flooding experiment shows that the residual leachate after consolidation of “5% CCAPT + cementitious slurry” contains only 35.6 μg/L of Pb and 29.2 μg/L of Zn. These concentrations are significantly lower than the national emission requirements. This study presents an experimental foundation for further investigation into the use of high-pressure jet grouting technology to seal tailings ponds.

Hydrogen permeation under high pressure conditions and the destruction of exposed polyethylene-property of polymeric materials for high-pressure hydrogen devices (2)-

Aiming to elucidate physical property affecting to hydrogen gas permeability of polymer materials used for liner materials of storage tanks or hoses and sealants under high-pressure environment, as model materials with different free volume fraction, five types of polyethylene were evaluated using two methods. A convenient non-steady state measurement of thermal desorption analysis (TDA), and steady-state high-pressure hydrogen gas permeation test (HPHP) were used both under up to 90 MPa of practical pressure. The limit of TDA method of evaluation for the specimens suffering fracture during decompression process after hydrogen exposure was found. Permeability coefficient decreased with the decrease of diffusion coefficient under higher pressure condition. Specific volume and degree of crystallinity under hydrostatic environment were measured. The results showed that the shrinkage in free volume caused by hydrostatic effects of the applied hydrogen gas pressure decreases diffusion coefficient, resulting in the decrease of permeability coefficient with the pressure rise.

Influence of aging on hydro-mechanical behavior of unsaturated ballast

To better understand adverse impacts of aging on track maintenance, the hydro-mechanical behavior of unsaturated fresh and aged ballasts was investigated by means of saturated permeability tests, water retention tests, and monotonic loading triaxial compression tests. Firstly, the aged ballast was prepared through the Los Angeles abrasion (LAA) test to reproduce the gradation and particle shape for in-situ aged ballast extracted from actual railway tracks in Japan. Moreover, the results of saturated permeability tests and water retention tests prove that aging induces a remarkable decrease in the saturated coefficient of permeability and a significant increase in water retentivity compared with fresh ballast, due to the presence of fine fraction content. For the shear strength, the effective shear strength parameters of fresh ballast under fully drained conditions (CD test) are close to those under fully undrained conditions (CU test), regardless of water content. However, for the aged ballast, due to the low permeability, it is difficult to simulate fully drained conditions with laboratory tests, even at a very low axial strain rate (0.01%/min). In this case, the effective shear strength parameters of aged ballast are more suitable to be determined by the CU test. Besides, the results of triaxial compression tests prove that aging reduces the effective internal friction angle of ballast, while it increases the total cohesion compared with fresh ballast, especially under the high saturation condition. Lastly, the shear strength of both materials has a decreasing tendency with increasing water content, and the declining trend of shear strength is more noticeable for aged ballast. Therefore, the effects of aging and moisture content on the hydro-mechanical behavior of the railroad ballast should be synergistically considered in the railway track design.

Effect of porous organic polymers in gas separation properties of polycarbonate based mixed matrix membranes

Polycarbonate (PC) based mixed matrix membranes (MMMs) loaded with porous organic polymers as fillers exhibit very good performance in gas separation of industrial interest. Resulting MMMs show excellent compatibility between the two phases.The MMMs were prepared in less time than the reported PC-based MMMs, by controlled addition of the filler under ultrasound stirring and magnetic stirring sequences. PC-based MMM loaded with 20% of un-functionalized and functionalized filler containing NO2 groups (PC@2Ph and PC@2PhNO2) showed very good performance because all gas permeability coefficients increased while the selectivity remained unchanged for most gas pair and even increased significantly respect to pure PC membrane. MMM prepared with the methylamino-functionalized filler (PC@2PhCH2NH2) showed a greater H2/CH4 and CO2/CH4 separation selectivity in comparison with PC, with a slight decrease in permeability coefficients. Compared with the PC-based MMM previously reported, PC@2Ph and PC@2PhNO2 were competitive for O2/N2 and CO2/CH4 and the best for H2/CH4 separation. The PC@KAPs membranes prepared in this work also improved the performance of PC to hydrogen and methane recovery, become in an attractive for petrochemical industry.

The Supramolecular Organization and Surface Morphology of Films of Poly(1-trimethylsilyl-1-propyne) with Different Configurational Compositions

The structure of the films of poly(1-trimethylsilyl-1-propyne) (PTMSP) with different configurational compositions (the concentration of cis-units of 40 to 80%) is analyzed in this study. The combination of X-ray diffraction analysis and atomic force microscopy makes it possible to reveal the peculiarities of the supramolecular organization and morphology of PTMSP films. The diffraction patterns of PTMSP films indicate an increase in the ordering of the supramolecular organization in the case of an increase in the concentration of cis-units, and the value of the characteristic interchain distance in PTMSP films does not depend on the fraction of cis-units. According to the data of atomic force microscopy, the surface of PTMSP films is characterized by the presence of cluster-like formations the size of which decreases with the increase in the concentration of cis-units (from 18.3 nm for PTMSP with the concentration of the cis-units of 40% to 6.8 nm for PTMSP with the concentration of cis-units of 80%). The decrease in permeability coefficients for O2 and N2 with an increase in the concentration of cis-units in PTMSP correlates with the increase in the ordering of the supramolecular organization and decrease in cluster size. The performed study shows that the structural features of the PTMSP films may be due to the effect of both the configurational composition of macrochains and relaxation processes accompanying the formation of a film obtained by evaporation on a substrate.

Effects evaluation of grass age on hydraulic properties of coarse-grained soil

This study investigates the effects of grass age on hydraulic properties of coarse-grained volcanic soil, namely: Komaoka soil. The soil-water characteristic curve (SWCC), unsaturated coefficient of permeability, outflow, runoff, and the variations in volumetric water content/matric suction under different rainfall intensities varying from 15, 30, 60, to 120 mm/h are measured by carrying out column tests. In addition, permeability tests are performed to determine the saturated coefficients of permeability of bare soil and grassed soils. In these tests, grassed soils with grass ages varying from 1 to 6 months are used to study the influence of root volume ratio on the hydraulic properties. The experimental results reveal that the grass age has an influence on the hydraulic properties of Komaoka soil. At the same volumetric water content, grassed soil with higher grass age has higher matric suction. Both saturated and unsaturated coefficient of permeability are significantly reduced with the increase in the grass age. Moreover, there is a decrease in the outflow and an increase in the runoff for grassed soil with higher grass age. Matric suction decreases later in grassed soil than that of bare soil under rainfall events. The higher the grass age, the longer time is taken to observe the change in matric suction. However, the matric suction of grassed soil is dramatically reduced while there is a gradual decrease in matric suction of bare soil. Furthermore, even though the matric suctions remain constant at somewhere in the vicinity of 2 kPa under long and intense rainfall events, higher volumetric water contents are recorded for grassed soil with higher age. The new model is proposed to estimate the unsaturated coefficient of permeability of coarse-grained soil due to the effects of grass roots. The good agreement between estimations and experimental results shows that the proposed model is useful to capture the decrease in unsaturated coefficient of permeability of grassed soil.

Effect of Salt Solution on Plasticity and Permeability of Vietnam’s Soil Liners

In Vietnam, there are a lot of landfills to block pollutants and one of materials used for impermeable liners is soil liners (soil – bentonite mixture). In order to use as impermeable liners, the properties of soil liners such as plasticity and permeability were affected by many salt solutions which are leaching from decomposition of waste materials in the landfills. Those salt solutions can reduce the stable of impermeable liners. So, this paper presents a series of experimental studies in the laboratory to investigate the effect of some salt solutions on the properties of compaction, consolidation and plasticity of soil liners. The experimental results indicated that the salt concentration effected complex on the Atterberg limits and the vertical coefficient of permeability. It also found that increase in the salt concentration from 0N to 0.05N cause increase in plasticity index, liquid limit and decrease in the vertical coefficient of permeability. After that, the increasing of the salt concentration up to 1N resulted in decrease in the liquid limit and plasticity index and increase in the vertical coefficient of permeability increases.

The Reduction of the Permeability of a Lateritic Soil through the Application of Microbially Induced Calcite Precipitation

Lateritic soils are frequently utilised in tropical areas of the developing world as an engineering material in the construction of rural earth roads, usually in the form of engineered natural surface (ENS) roads. The heavy, seasonal rainfalls common to the tropics results in ENS roads becoming quickly saturated with rainwater, and no longer accessible to motorised transportation. Microbially induced calcite precipitation (MICP) has been successfully used as a treatment process to decrease the permeability of clean, cohesionless sands by studies trying to impede the movement of groundwater, and any pollutants they may contain. In order to see if MICP treatment can also reduce the susceptibility of ENS road lateritic soils to rainwater saturation, this study has treated a Brazilian sample extracted from an ENS road in Espirito do Santo, Brazil, using the MICP bacterium Sporosarcina pasteurii contained within a urea-calcium chloride solution inoculum. Investigation, by means of a Rowe cell, of the post-treatment permeability, to untreated control samples, has shown an average decrease in the vertical coefficient of permeability of 83%, from 1.15 × 10-7 m/s for the untreated control samples, to 1.92 × 10-8 m/s in treated samples.

Aromatic block co-polyimide membranes for sour gas feed separations

Permeation properties of pure and gas mixture consisting of CO2, H2S, CH4, N2 and C2H6 through dense films of the block co-polyimides (6FDA-mPDA)-(6FDA-durene) are studied at 35–55°C and pressures of 100–500psi for combined separation of CO2, H2S and N2 from acid gas streams. The H2S composition in the gas mixture is up to 20vol%. This rigid block copolymer exhibits relatively constant or slightly decrease in pure gas permeability with increasing feed pressure for most of the penetrants. The pure gas CO2/CH4 and N2/CH4 selectivities are up to 61 and 2.6 respectively. The mixed gas studies also show relatively constant or slightly decrease in permeability coefficients with increase in pressure for most of the penetrants. One significant fact is that, at feed pressure of 500psi and 20vol% H2S in feed gas mixture (consisting of CO2, N2, CH4 and H2S), H2S/CH4 and CO2/CH4 separation factors are 23 and 27 respectively. These values are within the same order of magnitude or even better than those obtained in other state-of-the-art polymeric membranes that have been reported. Another unique feature of this co-polyimide is that, in addition to being selective to acid gas, it is also more selective to N2 as compare to CH4. Moreover, the CO2/CH4 separation factor does not suffer significant loss to the same degree as in the case of cellulose acetate (CA), even under these much more aggressive environments. This stability at moderate pressures and high H2S concentration is quite remarkable, as most reported studies are focused on low H2S concentrations and low pressures.

Selective removal of butanol from aqueous solution by pervaporation with a PIM-1 membrane and membrane aging

In this work, the selective removal of butanol from aqueous solution by pervaporation with a polymer of intrinsic microporosity (PIM-1) membrane was studied. The freshly cast and aged (370days) PIM-1 membrane was used for pervaporation experiments at 50°C. The aged PIM-1 membrane exhibited a decrease of permeability coefficient compared to the freshly cast membrane, from 9.0×10−5 to 1.1×10−5molm−1kPa−1h−1 for 1-butanol and from 3.2×10−5 to 2.2×10−6molm−1kPa−1h−1 for water, but simultaneously an increase of selectivity, from 2.8 to 5.1, for the separation process at 2wt.% of butanol. The aging effect may be attributed to slow rearrangement of polymer chains, resulting in densification and reduction of accessible free volume. Renewed soaking of an aged membrane with methanol does not restore the original permeability. The selectivity of 1-butanol increases with higher 1-butanol concentration for fresh PIM membrane, however the opposite trend was observed for aged PIM-1 membrane.

Study on the Permeability of Reinforced Soil with Herb Fiber under Different Salt Solution Concentration

The best is to read these instructions and follow the outline of this text. n this investigation, laboratory permeability tests were conducted on the wet-processing reinforcement specimens to study the feasibility of reinforced soil as a material of construction. Two kinds of reinforced specimens with different reinforcement materials (wheat straw (C) and flax (M)) were mixed with 3% contents of soil mass, and product to the cylindroid for measurement of permeability by a flexible-wall permeameter. The variation relationship between permeability coefficient and Na2SO4 concentrations was analyzed. Test results show that the liquidity reduced with incrassate diffusion layer caused by the increasing Na+ concentrations in the diffusion layer of soil particles, and then a decrease of permeability is found. With the increasing time of permeability, it is found that the permeability coefficient decreased due to the consolidation and decreasing porosity of specimens caused by the change of stress state. At the same time, ion exchange adsorption and water film incrassate occurs in soil particle surface which also benefit to the decrease of permeability coefficient.

Material properties of portland cement paste with nano-montmorillonite

The nano-montmorillonite, which has characteristics of high aspect ratio and interaction between polymer chains and dispersed nanolayers, has been widely used in the development of new reinforced nanocomposite polymers to improve their mechanical properties. Since a potential pozzolanic reaction may occur between Portland cement paste and high amount of silicon dioxide (SiO2) in nano-montmorillonite, the effects of introduction of montmorillonite to Portland cement-based material on the improvement of matrix properties of cement paste is of great interest in the construction industry. In this study, a liquid-form of nano-montmorillonite particle with a planar diameter of about 100 nm were incorporated into the Portland cement paste at five different dosages and analyzed at four different ages to identify the nanosizing effects on material properties of such cement-based composite. Experimental results show that the composite with 0.60% and 0.40% of added nano-montmorillonite by weight of cement have the optimum compressive strength and permeability coefficient, respectively, in which the increase of compressive strength is about 13.24%, and the decrease of permeability coefficient about 49.95%. Microstructural properties through the analyses of XRD, DSC, NMR, and MIP also indicate that the microstructures of cement paste with nano-montmorillonite contain more dense solid material and more stable bonding framework.

Transport of Cr(VI), Zn(II), and Cd(II) Ions Across Polymer Inclusion Membranes with Tridecyl(pyridine) Oxide and Tri-n-Octylamine

ABSTRACTAn experimental investigation of chromium(VI), zinc(II), and cadmium(II) ions removal from acidic chloride aqueous solutions by transport through polymer inclusion membrane (PIM) with basic ion carriers [i.e., 4-(l′-n-tridecyl)pyridine N-oxide (TDPNO) and tri-n-octylamine (TOA)] is presented. The initial fluxes of all metal ions are higher for the less basic carrier (i.e., TDPNO). On the other hand, the more basic carrier (i.e., TOA) gives higher Cr(VI)/Cd(II) and Cr(VI)/Zn(II) selectivity coefficients. In long-term chromium(VI) transport experiments, the aqueous source and receiving phase were renewed every day, whereas the PIM remained the same as in the first run: the small decrease of permeability coefficient was observed, which can be explained by the partitioning of the carrier between the membrane and the aqueous solutions. A long-term experiment was conducted out to demonstrate the durability of PIMs. The application of PIM transport process for 99% removal of chromium(VI) from galvanic wastewaters is also shown.

Removal of chromium(VI) from aqueous solutions by polymer inclusion membranes

The transport through polymer inclusion membranes (PIMs) was found as the effective and selective method of chromium(VI) anions removal from chloride acidic aqueous solutions. The optimal PIMs content was as follows: 41 wt% of cellulose triacetate as the support, 23 wt% of tri- n-octylamine as the ionic carrier, and 36 wt% of o-nitrophenyl pentyl ether as the plasticizer. The results obtained show a linear decrease of permeability coefficient and initial flux values with source phase pH increase. Also linear decrease of initial flux in log–log scale with chromium(VI) concentration increase was observed. Value of slope of this relationship was found to be 0.96 which indicates a first order of chromium(VI) reaction with tri- n-octylamine at membrane/aqueous source interface. Transport of chromium(VI) through PIMs reduces the concentration of chromium(VI) in source aqueous phase from 1.0 to 0.0028 ppm, which is below permissible limit in drinking water in Poland. Competitive transport of chromium(VI), cadmium(II), zinc(II), and iron(III) from acidic aqueous solution across PIMs was found to be efficient for chromium(VI) (99%), and cadmium(II) (99%).

Lime stabilization of inorganic contaminants in clays

Abstract The legacy of industrial operations over the past 200 years are contaminated natural clays and clay-based sediments. There is an urgent need for economic methods to stabilize these materials since the problem is widespread. Chemical fixation or encapsulation of inorganic contaminants using lime provides one potential solution that has yet to be adequately explored. This paper aims to review the methods of chemical stabilization of inorganic contaminants using pozzolanas, and in particular discuss the interaction of clays with both metal ions and lime. The parallels between cement, lime-fly ash and lime-clay stabilization reactions are examined to determine the potential for contaminant stabilization using lime and suggest the mechanisms upon which success would rely. The factors affecting the lime stabilization process are discussed. Methods of incorporation of lime in practice are thereafter discussed, covering deep mixing as well as surface mixing in situ and mixing ex situ . Specific research required to prove the potential of lime is then discussed. The paper concludes that lime stabilization provides a potentially valuable and economic means of treating both natural clays and (often very wet) clay-rich sediments. This is achieved via both enhanced contaminant adsorption and precipitation of metal ions under conditions of high pH, and binding in of the contaminants with the reaction products of the pozzolanic reaction between lime and clay. However, the fundamental nature of the clay/sediment is altered by the lime-clay reactions, most notably in the context of future potential for ion mobility by an immediate increase followed by a progressive decrease in coefficient of permeability. The degree to which inorganic contaminants become associated with the reaction products and the permanency of this association under conditions of seepage (i.e. resistance to leaching) need to be researched in detail before confidence in the technique can be engendered.

Gas transport properties of soluble poly(phenylene sulfone imide)s

Gas transport of helium, hydrogen, carbon dioxide, oxygen, argon, nitrogen, and methane in three soluble poly(phenylene sulfone imide)s based on 2,2-bis(3,4- decarboxyphenyl) hexafluoropropane dianhydride (6FDA) has been investigated. The effects of increasing length of well-defined oligo(phenylene sulfone) units on the gas permeabilities and diffusivities were determined and correlated with chain packing of the polymers. Activation energies of diffusion and permeation were calculated from temperature-dependent time-lag measurements. The influences of the central group in the diamine moiety of 6FDA-based polyimides on physical and gas transport properties are discussed. The incorporation of a long oligo(phenylene sulfone) segment in the polymer backbone decreases gas permeability and permselectivity simultaneously. The decreases in permeability coefficients can be mainly related to decreases in diffusion coefficients. Changing the central group of diamine moiety from {S{ to {SO2{ leads to a 45-50% decrease in CO2 and O2 permeabilities without appreciable increase in the selectivities. This is considered to be due to the formation of charge transfer complexes. q 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1855-1868, 1997

Gas transport properties of poly(phenylene thioether imide)s

Gas transport of carbon dioxide, oxygen, nitrogen and methane gases in a series of poly(phenylene thioether imide)s based on 2,2-bis(3,4-decarboxyphenyl) hexafluoropropane dianhydride and diamine-terminated oligo(phenylene thioether)s has been investigated. The effects of the oligo(phenylene thioether) length on the gas permeabilities and diffusivities were determined and correlated with chain packing of the polymers. The incorporation of a long oligo(phenylene thioether) segment in the polymer backbone decreases gas permeability and permselectivity simultaneously. The decreases in permeability coefficients can be related to decreases in both the diffusion coefficients and the solubility coefficients of all the gases. Finally, the physical and gas transport properties are simply compared between poly(phenylene thioether imide)s and poly(phenylene thioether).

Permeability of acetic acid across gel and liquid-crystalline lipid bilayers conforms to free-surface-area theory

Solubility-diffusion theory, which treats the lipid bilayer membrane as a bulk lipid solvent into which permeants must partition and diffuse across, fails to account for the effects of lipid bilayer chain order on the permeability coefficient of any given permeant. This study addresses the scaling factor that must be applied to predictions from solubility-diffusion theory to correct for chain ordering. The effects of bilayer chemical composition, temperature, and phase structure on the permeability coefficient (Pm) of acetic acid were investigated in large unilamellar vesicles by a combined method of NMR line broadening and dynamic light scattering. Permeability values were obtained in distearoylphosphatidylcholine, dipalmitoylphosphatidylcholine, dimyristoylphosphatidylcholine, and dilauroylphosphatidylcholine bilayers, and their mixtures with cholesterol, at various temperatures both above and below the gel-->liquid-crystalline phase transition temperatures (Tm). A new scaling factor, the permeability decrement f, is introduced to account for the decrease in permeability coefficient from that predicted by solubility-diffusion theory owing to chain ordering in lipid bilayers. Values of f were obtained by division of the observed Pm by the permeability coefficient predicted from a bulk solubility-diffusion model. In liquid-crystalline phases, a strong correlation (r = 0.94) between f and the normalized surface density sigma was obtained: in f = 5.3 - 10.6 sigma. Activation energies (Ea) for the permeability of acetic acid decreased with decreasing phospholipid chain length and correlated with the sensitivity of chain ordering to temperature, [symbol: see text] sigma/[symbol: see text](1/T), as chain length was varied. Pm values decreased abruptly at temperatures below the main phase transition temperatures in pure dipalmitoylphosphatidylcholine and dimyristoylphosphatidylcholine bilayers (30-60-fold) and below the pretransition in dipalmitoylphosphatidylcholine bilayers (8-fold), and the linear relationship between in f and sigma established for liquid-crystalline bilayers was no longer followed. However, in both gel and liquid-crystalline phases in f was found to exhibit an inverse correlation with free surface area (in f = -0.31 - 29.1/af, where af is the average free area (in square angstroms) per lipid molecule). Thus, the lipid bilayer permeability of acetic acid can be predicted from the relevant chain-packing properties in the bilayer (free surface area), regardless of whether chain ordering is varied by changes in temperature, lipid chain length, cholesterol concentration, or bilayer phase structure, provided that temperature effects on permeant dehydration and diffusion and the chain-length effects on bilayer barrier thickness are properly taken into account.

Percutaneous Penetration of β-Blocking Agent-Fatty Acid Ion

The flux of β-blocking agents increased by an ion-pair formation in the presence of fatty acids. In case of oxprenolol-caprate, it was found that the contribution of this ion-pair to the flux was about 98 % and it had a high permeability coefficient almost close to that of oxprenolol base. We compared the enhancing effect of the ion-pair formation both in the water vehicle and in the lipophilic vehicle. We analyzed the penetration enhancing effects on the basis of the two-layer skin model. In case of water vehicle, we found this enhancing effect was caused by the increase of partition coefficient between the vehicle and stratum corneum, and that ion-pair formation didn't increase the diffusion coefficient in the skin. In water vehicle only a small amount of drug could be absorbed through the skin, because of the low solubility of the lipophilic ion-pair, although it had high permeability coefficient. Therefore IPM was used as lipophilic vehicle. We experimented using IPM saturated with ion-pair. We found that the maximum flux value of propranololcaprylate and oxprenolol-caprate were about 3 and 4 times respectively higher than that of their bases, being caused by high solubility in IPM and high permeability coefficient. The permeability coefficient, however, decreased with the increase of lipophilicity of ion-pair. With the use of two-layer skin model it was proved that the decrease of permeability coefficient was caused by the decrease of its partition coefficient between the stratum corneum and the viable epidermis. It can be said that ion-pair formation bring about different effects in penetration process dependent upon what vehicle it is dissolved in.