Concentration Of Surface-active Agent Research Articles

Influence of noncoherent nucleation on the formation of the polycrystalline structure of metals electrodeposited in the presence of surface-active agents

The formation of the polycrystalline structure of metals electrodeposited in the presence of surface-adsorbed foreign particles was theoretically simulated according to the model of noncoherent nucleation when the substrate does not influence the process any more. Performing a thermodynamic-statistical analysis, it was possible to relate quantitatively the structural parameters of the deposits (average grain size and dislocation density) to the relative decrease of the linear free energy of the nucleus boundary due to surface adsorption of foreign particles. The theoretical results were discussed in connection with our experimental findings on potentiostatic copper electrodeposition in the presence of thiourea. In agreement with theory, by increasing the surface-active agent concentration in the electrolyte, the average grain size decreased while the dislocation density strongly increased. Moreover, the microstructure of the deposit cross-section gradually changed from the columnar to the homogeneous type, becoming completely homogeneous for a thiourea concentration higher than 10 mg l −1 . Furthermore, the density of the twin boundaries gradually decreased, as may be expected on the basis of an increased selective adsorption of thiourea molecules on the twinning planes of the deposits.

Digital Image Analysis to Assess Microbubble Behavior in Porous Media

Air sparging is a commonly implemented technology for the remediation of volatile organic compounds from contaminated soil and ground water. In the sparging process, air is pressurized into the soil/ground-water matrix through injection wells. The air then travels to the ground surface through buoyancy, acting as a collector for volatile chemicals. To date, the design and implementation of air sparging has been largely empirical, based on the results of pilot studies. This paper uses digital image analysis to examine the transport and coalescence behavior of microbubbles in porous media, one of the most important control parameters for contaminant removal in air sparging. This laboratory study compared the diameter of bubbles produced in aqueous systems with the diameters produced in uniform spherical particulate media (diameters of 14.5 and 27.0 mm) and in elliptically shaped particulate media (equivalent spherical diameters of 14.5 mm). Results showed that the presence of a particulate media increased the average diameter and also increased the range of diameters of bubbles produced during sparging. As the diameter of the particulate media increased, the size of the bubbles decreased, indicating less coalescence in media with larger pore space. In addition, the effect of trace concentrations of surface-active agents (surfactants) on the diameter and coalescence behavior of bubbles was examined. In both aqueous and aqueous/particulate matrices, the presence of surfactants significantly decreased the average diameter of the bubbles produced. Additionally, the degree of coalescence decreased in the surfactant systems, producing a very narrow range of bubble diameters in both aqueous and aqueous/particulate media.

Low-cost HARMS process

A low-cost HARMS (High Aspect Ratio MicroSystems) process has been developed, which enables the fabrication of micromechanical parts or entire systems of metal. In comparison with the original LIGA process, this process is a truly low-cost one. Based on a state-of-the-art mask technique. UV-sensitive polymer and a self-built spray processor for resist development, structures with heights of 300 μm, lateral dimension of 30 μm, sharp sidewalls and aspect ratios up to 10 can be achieved. The developed moulds can be filled with metais (Ni, Cu) using electroforming. A proper control over some plating-bath parameters is imperative when no defects are allowed. Especially for a nickel(II)-sulfamate bath, temperature, particle filtration, periodic active carbon filtration of degenerated organics, pH measurement and monitoring of the nickel concentration are required. Monitoring the surface-active agent concentration is of great importance. Potentiometric tilration using a new tenside electrode allows determination of the agent and its decomposition products. Examples of gearwheels and planar coils in photoresist and metal are given.

Characteristics of water-base foam combustion

Systematic experimental studies have been carried out to characterize the combustion of water-base foams with various hydrogen- and methane-air mixtures. The dependencies of the combustion wave speed (S) on the expansion ratio of foam (K), concentration of surface-active agent (SAA) in detergent solution, and bubble size of foam have been investigated. The combustion of foams with hydrogen mixtures has been established to be steady state. The effects of unsteadiness arising from combustion of methane foams are due to sound generation in the system and its interaction with the flame. The flame speed in foam with rapidly burning gas mixture has been demonstrated to decrease with decreasing expansion ratio and the foams with slowly burning mixtures have demonstrated to be a non-monotonic function of K, including an anomalous region of increasing flame speed with decreasing K. It has been demonstrated that the increase in both the SAA concentration in a detergent solution and the mean size of foam bubbles have no effect on the form of S(K) dependence but leads, however, to the increase in the flame speed values. The characteristics of foam combustion have been shown to be due to the effects of heat transfer from the gas to foammore » films and aerosol droplets forming upon destruction of foams by a flame front. Taking into account the interphase interaction provided the basis for derivation of a simple model of foam combustion and allowed to predict the flame speed dependences on the controlling parameters. The characteristics of combustion predicted by the model are in fair agreement with experimental data.« less

Influence of manufacturing parameters on the size characteristics and the release profiles of nifedipine from poly( DL-lactide-co-glycolide) microspheres

Empty or nifedipine-loaded biodegradable poly( dl-lactide-co-glycolide) microspheres were prepared by the solvent evaporation method. Spherical microparticles of different size distribution were thus obtained. The evolution of the mean diameter and the extent of size distribution as a function of different preparation parameters were studied. The mean particle diameter decreased when the stirring rate, the surface-active agent concentration and the internal phase volume were increased. Microspheres of 12, 18 and 83 μm, with different nifedipine payloads were obtained. The in vitro release of the drug was evaluated under sink and non-sink conditions: the 12 and 18 μm microspheres provide the same linear profile for approx. 400 h. Under non-sink conditions, the 83 μm microspheres exhibit an S-shape release pattern.

Paper Chromatographic Observation on the Effects of Surface Active Agents to Remove the Soil on Fiber Assemblies

Paper chromatography was conducted for examination of the physico-chemical effects of detergents for removing water insoluble soils on fiber assemblies without mechanical and/or hydrodynamic force. Using cellulose filter paper as the fiber assembly for the fixed phase and C.I. Disperse Blue 3 as a model of water insoluble soil, the relation between Rf' and the concentrations of surface active agents was examined.The Rf', a measure of detergency, increased steeply near a critical micellar concentration of each surface active agent. In such a case, the longer the chain length of the alkyl group in the alkylsulfate, the lower was the concentration necessary to increase Rf' to give higher detergency. In dodecyl poly (oxyethylene) ethers, the shorter the chain length of the oxyethylene group, the lower was the concentration needed to increase Rf'. On adding NaCl to an aqueous solution of sodium dodecyl sulfate (SDS), the SDS concentration required to increase Rf' was lowered by the builder effect. Ionic surface active agents showed lower Rf' at higher temperature, while nonionic agents showed higher Rf' at high temperature.By application of a theoretical equation to pseudophase liquid chromatography, the detergency of Disperse Blue 3 as a model of soils could be explained on the basis of the solubilization mechanism.

Enteric spherules diastase in enzyme preparations

Enteric diastase spherules were prepared using cellulose acetate phthalate and eudragit RS-100 by emulsion solvent removal method. Factors that could affect the size shape and diastatic activity were studied. The studied factors include pH of aqueous media, temperature of dispersion media and concentration of surface active agent. Prepared enteric diastase spherules were investigated for stability and diastatic activity at different temperatures and pH in various buffer systems, in the presence and absence of pepsin, a gastric enzyme. Eudragit RS-100 based spherules were noted to be spherical and uniform in shape with an appreciable level of diastatic activity. However, diastase was observed to be released from such a system in a slow but controlled manner. Eudragit RS-100 was found to provide more stabilization to the diastase than the stabilization provided by cellulose acetate phthalate. The spherules when tested in in vitro and in situ were recorded to exhibit diastatic activity at 99 per cent potency level (based on an actually incorporated amount of diastase). The study reveals that enteric or pH sensitive diastase releasing systems hold promise and potential in the therapeutic application of digestive enzyme(s).

Flocculation studies of granulated stearyl alcohol on the surface of aqueous media. II. Flocculation-deflocculation mechanism in a two-dimensional system.

The flocculation-deflocculation mechanism of granulated stearyl alcohol dispersed on the surface of aqueous media in the presence of surface-active agents was examined. The flocculation rate was estimated on the assumption of a second-order rate process. The flocculation rate decreased at first, and then increased to the maximum value with increasing concentration of the surface-active agent. Thereafter, the flocculation rate decreased, and reached an almost constant value. The profiles of change of the flocculation rate with concentration of surface-active agent in the systems containing various kinds of surface-active agents were similar. However, taking account of the critical micelle concentration, the profiles could be classified into two patterns. One reason for the difference between the profiles was supposed to be the difference in structure of the surface-active agents. The flocculation behavior is discussed in relation to the effects of hydrophobic interaction, electrorepulsive force and steric hindrance.

The Effect of Some Surfactants on the in- Vitro Properties of Double Compressed Tablets

AbstractThe effect of different types and concentrations of some surface active agents as well as the method of surfactant incorporation on the in - vitro properties of aspirin tablets as a model for double compressed tablets was studied. The formulated tablets were evaluated using the U. S. P. official tests and some other selected non-official tests. These tests include: uniformity of weight, uniformity of content, disintegration, dissolution, hardness, friability and thickness. Incorporation of a low concentration (0.2 % w/w) of surface active agents i n the formulation of tablets decreased the disintegration time but did not affect their dissolution rate. Higher concentrations of surface active agents retarded the dissolutiono of tablets. Non ionic surfactants showed higher regarding effect than ionic surfactants. Changing the method of surfactant incorporation did not greatly affect the dissolution rate of tablets.

Effects of Surface Active Agents and Builders on Fastness to Washing of Antibacterial Agents in the Latest Commercial Anticrobial Treatment Products

This paper describes the effects of surface active agent and builder on the fastness to washing of antibacterial agents in commercial anticrobial treatment products.The results obtained are as follows. (1) With regard to the effects of detergents on the fastness to washing of antibacterial agents, the antibacterial activity to Staphylococcus aureus IFO 3060 with sample No. 1 was large in the order of : washing with water, light duty detergent, liquid detergent, soap powder, according to inclinations of each regression curves. Because the width of clear zone when washed with detergent having high concentration of surface active agents is smallas shown in the results of antibacterial activity test. negative correlation was recognized between the concentration of surface active agents in detergents and the inhibition percent. This tendency was similer to other three test organisms. (2) With regard to the effects of the kind of surface active agent on the fastness to washing of antibacterial agents, the antibacterial activity to three test organisms with sample No. 2 was small in the order of : marseies soap, soap, AOS, AES, LAS, control washing with water. Furthermore, the builder also influences the antibacterial activity, the degree of the effect on the antibacterial activity was lager sodium tripolyphosphate than sodium silicate. And the additive effects by combining the surface active agent with the builder were recognized .As the antibacterial activity of antibacterial agents in commercial anticrobial treatment products, therefore, is lost rapidly by washing with the detergents having high concentration of surface active agents, such as soap powder, it is necessary to use the detergents having low concentration of surface active agents and builders to keep the antibacterial and antifungal activities of antibacterial angents.

The Raman Spectra of Aligned Thin Films of Nematic Liquid Crystals

Abstract The Raman spectra of thin films of nematic liquid crystals, MBBA and NP-5A, have been measured for samples sandwiched between two glass (or quartz) plates, which had been pretreated in several ways. The intensities of the fundamental bands of the molecules and the polarization components of each band depend on the molecular orientation structures, such as the homogeneous and homeotropic alignments. The intensity ratio provides a semi-quantitative measure for the molecular orientation, and the Raman results are compared with those from polarizing microscopic observations and infrared spectra. The molecular orientation of the liquid crystals varies with the concentrations of surface-active agents as well as the materials used for the pretreatment of the plates. The molecular interactions, which give rise to the orientation structures, are briefly discussed.

The Study of the Relation between Concentration of Surface Active Agent and Critical pH in the Soluble Salt Flotation Method

The Study of the Relation between Concentration of Surface Active Agent and Critical pH in the Soluble Salt Flotation Method

Dynamic contact angles in mercury/carbon tetrachloride/solution systems. III. The mechanism and kinetics of spreading

The surface areas ( A) per molecule of several typical anionic and cationic surface-active agents at carbon tetrachloride/water, and mercury/water interfaces have been determined by the application of Gibb's adsorption equation. Whereas a limiting value for A at the carbon tetrachloride/water interface was of the order 54 Å 2, values at the mercury/water interface were three to five times higher. This was probably due to the incomplete orientation of the molecules at the mercury/water interface. Spreading in the mercury/carbon tetrachloride/solution system was controlled by the magnitudes of the interfacial forces. Because of the rapid rate of establishment of equilibrium excesses at the interfaces, compared with the rate of interfacial expansion (or contraction) these forces were effectively constant. The spreading processes were exponential and followed first-order kinetics of the form: dθ dt = K(θ eq − θ t) , where θ eq is the value of θ at t ∞, θ t the value at time t, and K a constant only for a particular concentration of surface-active agent; it is proportional to the rate of the spreading process. The energy of activation of the spreading process was found to increase with increase in concentration of each surface-active agent. At a unique and reproducible “critical” concentration of each of the ionic surface-active agents, the mechanism of the spreading process changed abruptly, and the magnitude of the energy of activation then effectively remained constant, i.e., independent of concentration. At low surface concentrations of the ionic surface-active agents (apparently chemisorbed on the mercury surface) a mechanism is proposed in which these molecules are compressed ahead of the spreading drop. As the surface concentration increased, however, a situation was reached where this compression mechanism was no longer possible, due to the dense packing of surface-active molecules. After this stage, the drop proceeded to spread over the adsorbed layer of surface-active molecules. It has been shown that spreading coefficients can not only predict the position of the equilibrium stage but in some cases the speed of a spreading process as well. Better agreement may have been obtained if the difficulties involved in a change in mechanism of the spreading process had not occurred.

The Effect Of Specific Conductivities of Oil and Water Phases on the Critical Voltage of Emulsification

The electric emulsification by the use of high voltages has been carried out to produce aerosols. However, , the present authors succeeded in producing directly O/W or WIO type emulsions by using fairly low voltages, during the course of studies on electrocapillary phenomena at oil/water interfaces. The critical voltage of emulsification E., i. e. the minimum voltage necessary to produce a continuous emulsification, had no direct relationship with the equilibrium interfacial tension r measured by the ordinary drop-weight method. Concentrations of inorganic electrolytes and ionic surface active agents in the oil and/or water phases had strong influences on Ee. The effect of the concentration of surface active agent, however, was found to be due primarily to its property as an electrolyte, the surface activity playing the secondary role. lt is the necessary condition for the electric emulsification that the specific conductivity of the discontinuous phase is higher than that of the continuous phase. Ne emulsification takes place when the latter is higher. Although the experiments were maiRly carried out in the waterlfuethylisobutylketone system, the same condition can be applied to other systems. For instance, mercury/water and liquid/air (aerosols) systems, for which most studies on electric emulsification were carried out, also satisfy this condition.

Influence of surface active agents on the mass transfer across liquid—liquid interfaces—I. Dioxane—toluene—water-system

The instantaneons concentration of dioxane in freely suspended single toluene droplets was measured for an extremely wide range of droplet ages (0—600 sec) by means of a modified scintillation technique and the age dependence of the overall coefficients of mass transfer was evaluated. With increasing droplet age four consecutive exchange processes dominate with different decay constants for the concentration of solute which have very high, high, low, and very low exchange rates due to interfacial disturbances, turbulent internal mixing, transient internal mixing and desorption from the interface respectively. The decay constants of the first two processes decrease and the last two remain constant with increasing concentration of surface active agents. The overall decay constant decreases, goes through a minimum, increases, passes a maximum and finally decreases with increasing concentration of surface active agents. An explanation for this behaviour is given.

SCHOTTEN‐BAUMANN esterification of poly(vinyl alcohol). III. Preparation of some photosensitive polymers and the effects of surface active agents on the interfacial esterification

AbstractSome of the photosensitive polymers, poly(vinyl p‐azidobenzoate), poly(vinyl p‐nitrobenzoate), poly(vinyl 2‐methyl‐5‐phenyl‐2,4‐pentadienoate), and poly(vinyl cinnamate co vinyl cyanoethyl ester), are prepared by SCHOTTEN‐BAUMANN esterification of poly(vinyl alcohol). The preparations of the acid halides and polymers are reported in details. The study of the effects of surface active agents on the esterification process shows the following results. When nonionic and anionic agents were added into the reaction system, the yield of the product increases with decreasing concentration of surface active agents and becomes a linear function of the concentration ending at the point at which no surface active agent is present. The linearity is observed in a wide range of concentration of the anionic agent, but not in the case of the nonionic one. The cationic agent drastically inhibits the reaction even at very low concentrations. These phenomena are explained on the basis of the reaction mechanism proposed in a previous paper.Applying the esterification process to a polyelectrolyte the reaction occurs only in the presence of salts as KBr, NaNO3 etc. This phenomenon is also explained by the reaction mechanism.

ON THE INTERACTION OF SURFACE ACTIVE AGENTS WITH SERICIN (PART 2)

The interaction of surface active agents with sericin has been studied with regard to reelability of cocoon in the process of raw silk production.The following results were obtained.1) Anionic and cationic surface active agents were adsorbed on sericin at co-ion regions respectively, and the adsorption of the later took place at pH2.5 where COOH groups of sericin scarecely dissociated.2) In the co-ion region, the charge density of AgI sol particles covered with sericin became noticeable at about 10-4M concentration of surface active agents, and at about cmc it increased remarkably. Also, the surface active agents which have the same polar groups increased the charge density of AgI sol particles covered with sericin at lower concentrations with the increase in chain length of alkyl groups.3) The increment of charge density of AgI sol particles covered with sericin by adsorption of surface active agents was observed in the order of counter ion>isoelectric point>co-ion region. This was also found in the adsorption test using cocoon layers.4) The effect of surface active agents on the swelling ratio of cocoon layer was in the order of co-ion>isoelectric point>counter ion region. In the counter ion region, the swelling ratio decreased at around the concentration at which the charge of sericin was neutralized with surface active agent, while in the co-ion region it increased remarkably at about cmc. Similar phenomena were found in the solubility test of sericin with sodium lauryl sulfate.From these results, it is concluded that the interaction of surface active agent with sericin is due to both van der Waals force and electrostatic force (Coulomb's force) and the swelling ratio of cocoon layer treated with surface active agent is influenced by intermolecular electrostatic repulsion of sericin due to the adsorption as well as by lowering of the surface tention or contact angle etc.

Salt effects in foam films

Measurements have been made of the excess tensions, equilibrium thicknesses and compositions of aqueous foam films stabilised by either n-decyl methyl sulphoxide or n-decyltrimethylammonium n-decyl sulphate and containing inorganic electrolyte. Two types of equilibrium film were obtained. The “second black” film formed at low electrolyte concentrations had a thickness of about 5 nm which was almost independent of electrolyte concentration, while the thickness of the “first black” film formed at higher electrolyte concentrations was much larger but decreased as the ionic strength increased. It is postulated that the abrupt transition from one type of film to the other was a specific ion adsorption effect, probably adsorption of the anion since the transition was more sensitive to changes in the anion than the cation. The variation of excess tension with electrolyte concentration in the first black films was in excellent agreement with the predictions of the DLVO theory of colloid stability using a simple single frequency dispersion force summation model to calculate the van der Waals energy. The large variations of excess tension of the second black films could not be explained quantitatively however. The excess tensions of both first and second black films were independent of temperature over the range 298 to 308 K, and there was no difference between the concentrations of surface active agent in the first and second black films.

The Adsorption of Surface Active Agents at Oil-Water Interfaces Considered from the Electrocapillarity

The adsorbability of surface active agents at oil-water interfaces and the influence of various norganic electrolyte on it were investigated by making electrocapillary curves. The oil phase was the solution of tetrabutylammonium chloride in methylisobutylketone, and the aqueous phase contained anionic, cationic or nonionic surface active agents in addition to the inorganic electrolyte. It was found that the interfacial tension decreased over the anodic or cathodic polarization range, depending upon whether the surface active agent was anionic or cationic. This decrease was strongly influenced by the kind and concentration of the electolyte in the aqueous phase.Linear relations held between the interfacial excess of the surface active agent and the cubic root of surface active agent concentration of the aqueous phase, as well as between the former and the cubic root of the ionic strength of the aqueous phase. These were in good agreement with Davies' equation derived theoretically. For alkylsulphate ions of various chain length, the free energy of desorption was calculated to be ca. 750 cal mol-1 for each -CH2- group.

Statistical analysis of detergency tests with a natural soil

AbstractFactorial experiments are described for detergency tests using a natural soil. The tests are carried out over several soil‐wash cycles using soil rubbed onto test swatches from the surface of the skin. The significance of the results is increased by removing the variability of soiling among different individuals from the wash treatment totals and by using a log transformation on the original data. Factors investigated include wash water temperature, water hardness, concentration of surface active agent and concentration of builders.