THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR

1. The electrochemical behavior (concentration potential, anomalous osmosis, etc.) of collodion membranes is due to its acidic impurities. These impurities determine the possible charge density of the collodion—aqueous solution interfaces. This (possible) charge density is believed to be identical with the base exchange capacity of the interfaces under consideration. 2. The collodion preparations commercially available at present are too pure to yield membranes of sufficient activity for electrochemical membrane investigations. Crude collodion, a product which is only partially purified, shows considerable electrochemical activity because of its content of acidic impurities. 3. The inactive commercial collodion preparations can readily be activated by oxidation by virtue of the fact that oxidation increases the number of dissociable groups (carboxyl groups) on the collodion. The oxidation method of activating collodion may be applied to membranes as such as well as to collodion in bulk. 4. The recommended oxidizing agents are sodium and calcium hypochlorite and sodium hypobromite. A further group of effective and recommended activating agents are solutions of strong alkalies. Alkalies cause a complicated decomposition of nitrocellulose with the formation of nitrites (and probably other nitrous compounds). These nitrites act upon the collodion as oxidizing agents, thus causing activation. 5. Detailed descriptions of tested oxidation procedures for highly dried membranes, porous membranes, and bulk collodion are given in the text, the optimum conditions being different in the three cases. 6. Collodion membranes oxidized as such show a much higher electrochemical activity than any previously described. Highly dried membranes after oxidation give concentration potentials which approach the thermodynamically possible maximum more closely than any given in the literature. Porous membranes after oxidation show greatly increased concentration potentials and yield much greater electroosmosis when a current is passed through. These effects are reflected in the enormous magnification of the extent of anomalous osmosis. 7. The behavior of the porous membranes toward nonelectrolytes changes but little on oxidation. The volume of such membranes, as well as their per cent water content (pore space), remains constant within the limits of experimental error. From this observation and studies on the rate of filtration, it is concluded that the geometrical structure of membranes is but little changed on oxidation. 8. Collodion oxidized in bulk likewise yields very active membranes. Dried membranes prepared from activated bulk collodion consistently yield concentration potentials which approach the thermodynamically possible maximum very closely and are appreciably higher than any previously reported. Porous membranes prepared from bulk oxidized collodion show a degree of electrochemical activity surpassing anything described for the most active commercial collodion preparations. However, these membranes are less active than those oxidized as such. 9. Membranes prepared from different collodion preparations which behave fairly uniformly towards nonelectrolytes but very differently towards electrolyte solutions become similar in their behavior towards electrolytes after oxidation. 10. The geometrical structures of membranes prepared from different collodion preparations are essentially identical. The differences in their behavior towards electrolytes are due entirely to the electrochemical factor; i.e., the charge density at the water/collodion interface. 11. Certain general aspects of the foregoing experimental results are discussed briefly.

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THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR

The Journal of General Physiology ◽

10.1085/jgp.27.5.433 ◽

1944 ◽

Vol 27 (5) ◽

pp. 433-449 ◽

Cited By ~ 8

Author(s):

Karl Sollner ◽

Joan Anderman

Keyword(s):

Solvent Mixture ◽

Exchange Capacity ◽

Acid Number ◽

Electrochemical Activity ◽

Time Base ◽

Equivalent Weight ◽

Base Exchange ◽

Electrochemically Active ◽

Organic Solvent Mixture ◽

High Base

1. The electrochemical behavior ("activity") of collodion membranes depends upon acidic, dissociable groups located in the interstices of the membranes. The active groups can be determined by base exchange measurements. High base exchange capacity is always found with preparations of great "electrochemical activity;" medium and low base exchange capacities occur with electrochemically active as well as with inactive preparations. The observed base exchange capacity is determined by two factors: the inherent acidity of the collodion (its mean equivalent weight) and the submicroscopic micellar structure of the collodion. A comparison of the base exchange capacity of various collodion preparations and their inherent acidities therefore allows certain conclusions to be drawn concerning the relative availability of the micellar surfaces in the different preparations. 2. The inherent acidity of various collodion preparations, their "acid number," was determined by electrometric titration. Collodion in the acidic state, i.e. after exchange of all other cations for H+ ions, was titrated in an organic solvent mixture with alcoholic KOH using a quinhydrone electrode. Details of the experimental procedure are given in the paper. The acid numbers, expressed in milliliters of 0.01 N KOH per gram dry collodion, vary from 1.0 for a highly purified collodion preparation of very low electrochemical activity to 3.3 for a highly oxidized sample of very high activity. Acid numbers of about 1.5 (corresponding to an equivalent weight of about 67,000) are found both with inactive commercial and with fairly active oxidized preparations. The base exchange capacity of the same preparations in the fibrous state as measured after 48 hours of exchange time varies from 0.0013 ml. 0.01 N NaOH per gm. dry collodion for the most inactive preparation up to 0.26 ml. 0.01 N NaOH per gm. for the most active preparation. Thus the acid numbers over the whole range investigated differ only in the ratio of 1:3.3, whereas the base exchange values differ in the range of 1:200. 3. In the inactive preparation only one in 770 acid groups is available for base exchange, in the most active collodion one group in 13; values between these extremes are found with commercial and alcohol purified oxidized preparations. 4. The high base exchange capacity of the electrochemically active preparations is not so much due to their higher acid number as to their more open structure. This difference in structure is ascribed to the presence of a small fraction of low molecular weight material which inhibits normal formation and arrangement of the micelles. 5. Short time base exchange experiments with fibrous collodion indicate that the number of acid groups available for the typical electrochemical membrane functions may be estimated to be about 50 to 1000 times less numerous than those found in the 48 hour base exchange experiments. It is estimated that in membranes prepared even from the most active collodion not more than one in 500 acid groups may be available for the typical membrane functions; with the less active preparations this ratio is estimated to be as high as one in 1,000,000 or more.

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The significance of certain “single value” soil constants

The Journal of Agricultural Science ◽

10.1017/s0021859600053053 ◽

1933 ◽

Vol 23 (2) ◽

pp. 261-310 ◽

Cited By ~ 2

Author(s):

E. W. Russell

Keyword(s):

Soil Properties ◽

Pore Space ◽

Potassium Phosphate ◽

Clay Content ◽

Exchange Capacity ◽

Minor Importance ◽

Base Exchange ◽

Structure Information ◽

Cent Relative Humidity ◽

Definition Of

SummaryThe conclusions that have been arrived at from the foregoing statistical examination of the available data on the physical properties of the Natal soils used by Coutts are:(1) The base exchange capacity of the soil, as measured by Schofield's potassium phosphate buffer method, appears to be of predominant importance for predicting several of the soil properties, as for example the sticky point and the moisture content at 50 per cent. relative humidity. On the other hand, the clay content seems to be of quite minor importance in predicting these soil properties.(2) The information from the data supplied by the Keen-Raczkowski box indicates that ω, the weight of water held per gram of soil in the box is very closely correlated with the base exchange capacity of the soil, while the swelling and pore-space parameters are more complex. The swelling υ seems to be dependent on the base exchange capacity of the soil and a term probably representing the structure of the soil, while the pore space p seems to be dependent on the clay content and a soil structure term. By choosing an appropriate definition of the pore space practically all the structure information given by the swelling parameters is contained in it.

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THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR

The Journal of General Physiology ◽

10.1085/jgp.25.3.411 ◽

1942 ◽

Vol 25 (3) ◽

pp. 411-429 ◽

Cited By ~ 7

Author(s):

Karl Sollner ◽

Charles W. Carr ◽

Irving Abrams

Keyword(s):

Quantitative Measure ◽

Exchange Capacity ◽

Electrochemical Activity ◽

Electrical Behavior ◽

Exchange Method ◽

Base Exchange ◽

High Base ◽

Different Origins ◽

Theoretical Considerations ◽

Exchange Properties

1. Theoretical considerations lead to the conclusion that dissociable acidic groups present to a varying extent in different collodion preparations determine the electrochemical behavior of membranes cast from these preparations. It is further reasoned that the base exchange capacity of the collodion surfaces is the true quantitative measure of the abundance of the dissociable groups. 2. The concept of base exchange capacity and the base exchange method are discussed. The conditions which allow a purposeful application of the latter are stated. 3. The base exchange properties of a number of fibrous collodion preparations of different origins and after various types of treatment, having widely varying electrochemical activities, are determined. 4. With the chemical (titration) and physical (electrometric) methods employed, no regular correlation can be found between electrochemical activity and base exchange. The base exchange capacity which is necessary to cause even great electrochemical activity of collodion is extremely small. 5. Measurable to high base exchange capacity always seems to be associated with good or high electrochemical activity; but base exchange capacity too low to be definitely measurable with the available methods may be found with collodion preparations of high as well as with preparations of low electrochemical activity. 6. The bearing of these results upon the problem of the spatial and electrical structure of the collodion membrane is indicated briefly.

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Surface charging parameters of charged particles in symmetrical electrolyte solutions

Physical Chemistry Chemical Physics ◽

10.1039/d0cp02725a ◽

2020 ◽

Vol 22 (35) ◽

pp. 20123-20142

Author(s):

Hadi Saboorian-Jooybari ◽

Zhangxin Chen

Keyword(s):

Charge Density ◽

Surface Charge ◽

Electrolyte Solution ◽

Surface Charge Density ◽

Potential Surface ◽

Research Work ◽

Charged Particles ◽

Electrolyte Solutions ◽

Surface Charging ◽

Curvature Dependence

This research work is directed at development of accurate physics-based formulas for quantification of curvature-dependence of surface potential, surface charge density, and total surface charge for cylindrical and spherical charged particles immersed in a symmetrical electrolyte solution.

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The effects of electrolyte concentration, ion species and pH on the zeta potential and electrokinetic charge density of montmorillonite

Clay Minerals ◽

10.1180/0009855064140224 ◽

2006 ◽

Vol 41 (4) ◽

pp. 853-861 ◽

Cited By ~ 70

Author(s):

E. E. Saka ◽

C. Güler

Keyword(s):

Zeta Potential ◽

Charge Density ◽

Negative Charge ◽

Electrolyte Concentration ◽

Great Influence ◽

Electrolyte Solutions ◽

Ionic Species ◽

Positive Sign ◽

Ion Species ◽

Influence Of Ph

AbstractIn this study, the influence of pH, electrolyte concentration and type of ionic species (such as LiCl, NaCl, KCl, RbCl, CsCl, CaCl2, AlCl3) on the electrokinetic properties (zeta potential and electrokinetic charge density) of montmorillonite has been quantified. The zeta potential of montmorillonite particles did not change significantly with change in pH. The valencies of the ions have proven to have a great influence on the electrokinetic behaviour of the suspension. There is a gradual decrease in the zeta potential (from —24 mV to —12 mV) with increase in monovalent electrolyte concentration (from 10-4 M to 10-1 M). At any monovalent electrolyte concentration, the magnitude of the zeta potential increased with the electrolytes in the order Li+ > Na+ > K+ > Rb+ > Cs+. The zeta potential of the montmorillonite minerals in CaCl2 solutions illustrated the same behaviour as the monovalent cations. Less negative values were obtained for the CaCl2 electrolyte (∼–10 mV) due to the greater valence of the ions. A sign reversal was observed at an AlCl3 concentration of 5 x 10-4 M, and, at greater concentrations, zeta potential values had a positive sign (∼20 mV).The electrokinetic charge density of montmorillonite showed similar trends of variation in mono and divalent electrolyte solutions. Up to concentrations of ∼10-3 M, it remained practically constant at ∼0.5 x 10-3Cm-2, while for greater electrolyte concentrations the negative charge produced more negative values (–16 x 10-3Cm-2). The electrokinetic charge density of montmorillonite particles was constant at low AlCl3 concentrations, but at certain concentrations it increased rapidly and changed sign to positive.

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