Different Concentrations Of Salt Research Articles

Electrokinetic phenomena in amphoteric membranes

The membrane phenomena in an amphoteric membrane-single-electrolyte or mixed-electrolyte solution systems were examined. The mobilities of the ions within the membrane were evaluated from the relation between the transport number and membrane conductance after determination of the ionic concentration within the membrane. In the single-electrolyte system, the mobilities depending on the ionic charges were observed. The facts supported that ion-transport phenomena were mainly controlled by the electrostatic interaction between the ion-exchange sites and the ions within the membrane. On the other hand, the cation with the smaller valence was always excluded out of the membrane in the mixed-electrolyte system. When comparing the ratios of mobilities in the single-electrolyte system with those in the mixed-electrolyte system, large differences between them could be observed. It is conjectured that one of the reasons may be the difference in the Donnan adsorption salt concentration within the membrane.

Self-sustained oscillations of electric potential in a model membrane

A model membrane constructed from a Millipore filter, whose pores are filled with dioleyl phosphate molecules, exhibits a self-oscillation of the electric potential with a period of about a few seconds in the presence of a salt-concentration difference, pressure difference and/or electric current across the filter. In this paper, the effects of chemicals such as KCl, CaCl 2, pH and sucrose on the self-oscillation are investigated experimentally. These chemical substances are shown to alter the characteristic properties as the frequency of oscillation. Theoretical consideration of electrochemical interaction between these substances and DOPH molecules gives a fairly good explanation of the observed results.

Evaporation Kinetics in the Hanging Drop Method of Protein Crystal Growth

AbstractWe present an engineering analysis of the rate of evaporation of solvent in the hanging drop method of protein crystal growth. Our results are applied to 18 different drop and well arrangements commonly encountered in the laboratory. We take into account the chemical nature of the salt, the drop size and shape, the drop concentration, the well size, the well concentration, and the temperature. We find that the rate of evaporation increases with temperature, drop size, and with the salt concentration difference between the drop and the well. The evaporation possesses no unique half-life. Once the salt in the drop achieves about 80% of its final concentration, further evaporation suffers from the law of diminishing returns.

A common source of error in pH measurements.

Glass-electrode assemblies in which the reference half-cell contains a porous ceramic type of liquid junction are likely to produce misleading pH measurements under normal service conditions. The error arises from substantial liquid-junction potentials, associated with the porous ceramic plug, which vary with the ionic composition of the solution under test. The error is not revealed by conventional two-point calibration procedures, since the majority of standard buffer solutions have a similar total ionic strength, but will nevertheless be present when the unknown solution differs in ionic strength from the standardizing buffers. The size of the error is proportional to the ratio between the salt concentration in the standard buffers and the concentration present in the unknown solution, and varies from one electrode specimen to another. The fault was present in 24 out of 30 electrodes in normal use selected at random from seven laboratories, and the mean error was 0.2pH unit per 10-fold salt-concentration difference between standard and test solutions. It is estimated that errors of this order must be widespread in the recent literature. Older pH determinations are likely to be more reliable, since the original reference electrode design with a free-flowing liquid junction is apparently free from the artefact.

Chromatin Replication in Tetrahymena pyriformis

The chapter discusses the investigation of chromatin replication in Tetrahymena provided some unexpected evidence in favor of an altered conformation of chromatin in the immediate area of the replication fork, which would be consistent with the involvement of fixed structural entities at the fork region. With regard to the sites of replication within the nucleus, two distinct possibilities can be envisaged. First, the replication forks with their attendant proteins could be essentially free in the nucleoplasm and physically move along the chromatin strand from origin to termination. The opposite situation would be fixed points of replication within the nucleus, with the chromatin fibers passing over or through these fixed points during replication. The chapter at present unable to offer any satisfactory explanation for this discrepancy: the two obvious possibilities, that Tetrahymena and Drosophila differ in replicative mechanism, or that small differences in salt concentration, buffer type, etc., could cause a dramatic rearrangement of deposited histones, are both unattractive. It is currently examining histone deposition in other systems in an attempt to provide further insight into the question.

Probable Impacts of Various Range Improvement Practices on Diffuse Salt Production

During 1976 a study of soil profile salt concentrations and probable salt loading by surface runoff was made on 73 range improvement sites in Utah, Colorado, New Mexico, and Arizona. The range improvement practices studied included gully plugs, contour furrowing, pitting, pinyon-juniper chaining, and various sagebrush-control treatments. Results of these studies indicated that the impact of gully plugs and contour furrows on potential diffuse salt production is somewhat variable and may in fact indicate that these treatments have only a minor potential impact, probably because the overland flow route is not a major source of diffuse salt movement, at least on lands sampled in this study. On pinyon-juniper sites and the various sagebrush treatments, the lack of difference in salt concentrations between treated and untreated sites was the only consistent trend. In general the measured salt concentrations in surface soils of either pinyonjuniper or sagebrush sites present a problem of little concern as related to salt production within the major river basins. Salinity in the Colorado River is of major national concern, for not only has it resulted in losses to the regional economy, but also high salinity levels have aggravated relations with the Republic of Mexico. Even in its virgin state, the salt load of the Colorado River in its lower reaches was about 600-700 ppm. However, man’s development of water resources has affected both the quantity and quality of water supplies. Salinity levels in the lower reaches of the river now average 850 ppm with a predicted concentration of 1,300 ppm by the year 2000. The sources and causes of dissolved solids within the Colorado River are of importance; for if they can be identified, strategies may be developed for effective management and control. In addition, this information would allow estimates to be made of downstream costs associated with upstream salt production, thus facilitating the development of economic trade-offs on a basin-wide level. Recent estimates suggest that the largest single man-caused source of salinity is irrigation return flow, amounting to about a third of the total salt load. Natural sources such as salt wells and springs, plus concentration by evaporation, account for another third. The remaining salt load is attributed to diffuse sources Authors are graduate research assistant and associate professor, rangeland hydrology, Watershed Science Unit, College of Natural Resources, Utah State University, Logan,

Coupling Phenomena in Saturated Homo‐ionic Montmorillonite: III. Analysis

AbstractThe data presented in the first paper of this series are analyzed using the theoretical transport equations and the analytical expressions for the transport coefficients developed in the second paper of the series.When the electrodes of the system presented in Part 1 of this series are not shorted the predicted behavior corresponds precisely with the actual behavior.Upon shorting the electrodes, the data indicate that the actual shorting of the clay‐water system is not perfect, an indication that the electrodes cannot release and absorb Cl‐ ions infinitely fast. From the data the shorting efficiency is calculated. The flux of cations through the clay‐water system while the electrodes are shorted can then be calculated. The absolute value of this flux appears to be slightly larger than the value calculated from the decrease in time of the salt concentration difference in the two liquid compartments. This is likely due to the buildup of a salt concentration gradient in the membranes.

Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds

AbstractIrrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes.

Interface Geometry for Two-Layered Stratified Flow

Several flow situations exist involving density difference in which vertical density gradients are much larger than those in the horizontal direction. In the analysis of such flows, a common approach schematizes the flow as two distinct homogeneous layers. For example, in the case of an arrested wedge of warm water overlying cooler water in the vicinity of a power plant outlet, the interface is generally defined such that the vertically averaged velocity in the warm upper layer is zero, unless recirculation is occurring. For recirculation of cooling water, the discharges in both layers are nonzero. There are numerous other situations in which discharges in both layers are nonzero; e.g., thermally driven exchange flows, exchange flows as a result of differences in salt concentration, and buoyancy driven side-arm circulations to name a few.

Coupling Phenomena in Saturated Homo‐ionic Montmorillonite: I. Experimental

AbstractA series of experiments was performed to observe the effects of salt concentration differences across a thin layer of homo‐ionic montmorillonite. The water pressure difference, concentration difference, and voltage difference measured with electrodes reversible to the anion were observed as functions of time. A qualitative explanation of the observations is proposed.

The role of polyelectrolyte charge density and molecular weight on the adsorption and flocculation of colloidal silica with polyethylenimine

The polyethylenimine (PEI)-water-Ludox AM colloidal silica system was used as a model system to investigate the relationship of charge density and molecular weight of the polyelectrolyte on the adsorption and subsequent flocculation of oppositely charged colloidal particles. Narrow molecular weight fractions of PEI ranging from 1760 to 18,400 were prepared and characterized. Differences in polymer molecular weight, salt concentration, and pH were employed to vary the number of cationic charges per PEI molecule. At the concentrations of PEI required to initiate flocculation of Ludox AM, complete adsorption of PEI occurred regardless of molecular weight, pH, or ionic strength. However, at higher concentrations, adsorption increased with molecular weight, pH, and ionic strength. The flocculation results indicated that the relative importance between polymer bridging and electrostatic considerations is pH dependent. At pH 9 and greater, polymer bridging is the dominant mechanism of destabilization due to the low cationic charge of the PEI molecule. Howevei, at pH less than 9, charge interaction between PEI and colloidal silica is the dominant consideration. An inverse linear relationship was found between the logarithm of the molar concentration of PEI required to initiate flocculation and the logarithm of the cationic charge on the PEI molecule.

The regulation of corneal hydration by a salt pump requiring the presence of sodium and bicarbonate ions

1. The use of polyacrylamide gel salt bridges enables trans-membrane potentials to be measured to an accuracy of 20 muV over long periods.2. The technique is applied to measure electrical potentials across corneal endothelia of rabbits.3. In de-epithelialized corneas which translocate water, a spontaneous potential of 550 muV is found across the endothelium (tissue resistance 20 Omega cm(2)).4. This electrical potential (and water translocation) is reduced to zero when sodium is absent from the Ringer, and by about 80% when bicarbonate ions are absent. Removal of chloride has no such effect.5. Under a variety of conditions, the potential correlates with the observed translocation of fluid across corneal endothelium. The translocated fluid is shown to be isotonic with sodium in the Ringer and therefore the potential correlates with ;active' sodium transport.6. The potential and water translocation are abolished in the presence of ouabain at concentrations greater than 10(-5)M.7. The potential (lens-side negative) is of the wrong polarity to explain the net sodium transport (into the lens-side) by a sodium ion ;pump'.8. The current does not equal the net sodium flux under short circuit conditions. They differ in magnitude and polarity.9. A model is proposed where the endothelium ;pumps' salt out of the corneal stroma into the aqueous humour.10. Flux equations are derived for a condition where the membrane (corneal endothelium) separates an ion exchanger (corneal stroma) from free solution (aqueous humour), where the usual relationship for free-free solutions Deltapi = c(s)Deltamu(s) does not apply.11. The model is of use only when the stroma is well stirred. It may be used in whole corneas retaining their epithelium but it may not be used in de-epithelialized corneas.12. The model predicts that the presence of an ;active' salt flux out across the endothelium would create passive water and salt fluxes. The passive water flux would also travel out of the stroma across the endothelium; the passive salt flux would travel, in the opposite direction, into the stroma across the endothelium.13. The kinetics of the passive water efflux, as a swollen cornea reverts to physiological hydration (the temperature reversal phenomenon) are predicted extremely well if the ;active' salt flux is chosen at 3.3 x 10(-7) m-mole. cm(-2) sec(-1).14. The value of the active salt flux which cannot be measured directly is extrapolated to be somewhat greater than 2.8 x 10(-7) m-moles. cm(-2) sec(-1); in good agreement with that required by the model to explain the temperature reversal phenomenon.15. The model is further used to calculate the salt concentration difference across the endothelium (which drives salt passively into the stroma) at various stromal hydrations.16. When an appropriate salt concentration is applied across the endothelium of de-epithelialized cornea, it generates a potential of the same polarity and similar magnitude to that found across the endothelium of equilibrated whole cornea. The endothelium acts like a cation exchange membrane.17. Additionally the calculated salt concentration difference across the endothelium correlates well with the measured transendothelial potentials in whole cornea as the corneal hydration varies.18. It is concluded that the model of an endothelial neutral salt ;pump' regulating corneal hydration is self consistent. The spontaneous potential found across the endothelium could be caused by the consequential passive flux of salt in the opposite direction.

Chemico-Osmotic Effects in Fine-Grained Soils

A theory to describe the simultaneous coupled diffusional flow of salt and water in soils is summarized. Examination of the coupling effects indicated by the theory and a computer analysis of consolidation caused by chemico-osmotic coupling shows that the effects of coupling should increase as soil void ratio decreases and soil compressibility and salt concentration differences increase. Test results have shown that chemico-osmotic effects do not exist, and the rates of solution flow are in reasonable accord with theoretical predictions. Chemico-osmotic consolidation is likely to be small for most soils, except for very fine-grained active clays like bentonite. However, these and other studies have shown that chemico-osmotic coupling is capable of moving soil pore water and dissolved salts and that chemico-osmotic soil stabilization might be feasible in certain cases.

Influence of Cropping System on Salt Distribution in an Irrigated Vertisol1

AbstractField studies were conducted to determine the influence of cotton (Gossypium hirsutum L.) and grain sorghum [Sorghum bicolor (L.) Moench.] on salt distribution in a vertisol profile. Electrical conductivity of soil saturated pastes taken from the root zone (0 to 90 cm) after 4 years of sorghum ranged from 2.6 to 4.8 mmhos/cm but ranged from 4 to 7.6 mmhos/cm at 0 to 90 cm after 4 years of cotton. Chloride concentrations showed similar trends in that CI‐ concentrations were 9 to 12 meq/liter at 0 to 90 cm after sorghum, but were from 18 to 30 meq/liter at the same depth after cotton. The differences in salt concentrations in the soil profile after the two crops were attributed mainly to higher water infiltration rate after sorghum (5.81 cm/hr) than after cotton (1.23 cm/hr). The indicate that cropping practice can be an important factor in salt accumulation in clay soils and that the crops should be alternated to avoid excessive salt accumulation in the root zone.

Adsorption kinetics in the polyethylenimine–cellulose fiber system

AbstractThe rate of adsorption of fractionated polyethylenimine (PEI) from water onto regenerated cellulose fibers was studied as a function of the polymer diffusion coefficient. Differences in polymer molecular weight, salt concentration, and pH were employed to vary the diffusion coefficient which was measured independently by a free‐diffusion technique. The sorption rate was measured at the same conditions and found to increase with decreasing molecular weight, increasing polymer concentration, decreasing salt concentration, and increasing pH. A simplified rate equation based on diffusion control with Langmuirian adsorption in stirred solution was developed by utilizing the concept of a Nernst diffusional film. The equation was successful in predicting the relationship between adsorption rate and diffusion coefficient for most cases studied. It was found, however, that a very large barrier to mass transfer retards the adsorption rate. For the system studied it was concluded that this barrier is a result of diffusion into and subsequent adsorption onto the internal porous structure of the cellulose.

The Effects of Temperature on the Exudation Process of Excised Primary Roots ofZea mays

The fluid exudation rates and the ionic compositions of the exudates of excised maize roots have been determined in bathing media of o-1 mM, i -o mM, to o mM, and 50-0 mM KC1, each containing o-i mM CaCl2, at temperature intervals between 10 °C and 30 °C. Analysis of these data in terms of an osmotic model for excised root exudation shows that the observed temperature variation in fluid exudation rate is accounted for by the observed temperature variation in the osmotic driving force, the salt concentration difference from xylem fluid to bathing medium. Temperature variation in the osmotic permeability of the root and of the non-osmotic water flow are not significantly different from zero.

Osmotic Efficiency Coefficients Across Compacted Clays

AbstractMovement of solution through clays in response to salt concentration differences and in response to hydraulic pressure differences was measured. Rate of movement of solution in response to an “osmotic pressure” difference was divided by the rate of movement in response to an energywise equal hydraulic pressure difference to obtain osmotic efficiency coefficients. These osmotic efficiency coefficients are increased by saturating the clay with monovalent rather than divalent cations, using divalent rather than monovalent anions, decreasing the water content of the clay plug and by decreasing the average concentration of the outside solution. Effects of these factors on the osmotic efficiency are predicted by diffuse layer theory (negative adsorption of salt) and hydrodynamic considerations.

Mechanism of Fluid Exudation from Isolated Maize Roots

IT is commonly believed that salts are secreted into the xylem vessels of isolated roots by some mechanism involving metabolic energy and that the concomitant water movement is driven by the osmotic pressure gradient between xylem sap and the external medium. In particular, House and Findlay1 have found quantitative support for this process in maize roots. These workers considered that the exudation from the basal ends of isolated roots was described by: where Jw (cm3 exuded per cm2 of root surface area per sec) is the fluid exudation rate, LpRT(Csx − Cs0) is the net osmotic water flux from the external medium into the root and ϕw0 is net water flux independent of any osmotic gradient. This latter water flow might possibly be analogous to that found in many animal epithelial preparations bathed in identical salines. In equation (1), Lp (cm/sec atm.) is the osmotic permeability or, more correctly, the hydraulic conductivity of the roots to transverse water flow, R the gas constant, T the absolute temperature, Csx (mole/cm3) the osmolarity of salt (for example, potassium chloride) in the exudate and Cs0 the osmolarity of salt in the external medium. The observed difference in salt concentration (Csx − Cs0) is likely to depend not only on the net salt flux into some compartment, like the xylem, but also on the rate of water entry into this region.

Simultaneous Flow of Water and Salt Through Unsaturated Porous Media: I. Rate Equations

AbstractThe thermodynamic theory of irreversible proceses was used as a basis in developing two rate equations for the simultaneous movement of potassium chloride and water through porous media under isothermal conditions. The two rate equations are urn:x-wiley:03615995:saj2sssaj196503615995002900020010x:equation:saj2sssaj196503615995002900020010x-math-0001 where T is Kelvin temperature, Jw and Js are flux of water and salt, ΔP and ΔCs are the pressure and salt concentration differences across the sample, C̄s is the mean salt concentration, r is the concentration ratio, v̄w is the partial molar or specific volume of matric water, depending upon units selected for measuring Jw and R, Lww and Lss are the direct transfer coefficients for water and salt, and Lsw and Lws are the interaction or linked transfer coefficients. The equations were tested under conditions of flow through unsaturated kaolinite and Millville silt loam at constant temperatures of 15, 25, 35C. The results showed that the interaction coefficients, Lws and Lsw, were equal, suggesting that the Onsager theorem was met in both kaolinite and soil systems at the temperatures, pressure, and concentrations used.

Effect of Differences in Salt and Hydrogen Ion Concentration on the Fertilizing Ability of Avian Sperm

Semen from males of a flightless strain was diluted with solutions having different salt concentration and pH, and held at 50–52°F for 3–7 hours, following which it was inseminated into White Leghorn females. Varying concentrations and proportions of Na2HPO4 and NaH2PO4· H2O were used in the diluents. Fertility was maximum when the freezing point depression of the diluent was between .607 and .639°C, but decreased gradually outside of this range. There was little difference in fertility between pH 6.47 and 7.95, but outside of this range there was a marked decline. The optimum pH appeared to be between 7.03 and 7.27. Motility was found to be an approximate measure of fertilizing ability with varying salt concentration and a poor measure when varying pHs were used. Hatchability was not adversely affected when eggs were fertilized by diluted, stored sperm. Submitted on July 1, 1957