scholarly journals STABILITY OF SUSPENSIONS OF SOLID PARTICLES OF PROTEINS AND PROTECTIVE ACTION OF COLLOIDS

1923 ◽  
Vol 5 (4) ◽  
pp. 479-504 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Double Layer ◽  
Isoelectric Point ◽  
Electrical Double Layer ◽  
Protective Action ◽  
Solid Particles ◽  
Double Layers ◽  
Salting Out ◽  
Egg Albumin ◽  
Gelatin Films ◽  
The Stability

1. It is shown that the concentrations of different salts required to precipitate suspensions of gelatin-coated collodion particles in water are practically identical with the concentrations of the same salts required for the "salting out" of gelatin from aqueous solutions. Neither effect shows any relation to the electrical double layers surrounding the particles. 2. It is shown that at the isoelectric point of gelatin, suspensions of gelatin-coated collodion particles are not stable and it had been shown previously that gelatin is least soluble at the isoelectric point. The addition of salt increases both the solubility of gelatin in water as well as the stability of suspensions of gelatin-coated collodion particles in water, and both effects increase with the valency of one of the ions of the salt. 3. This latter effect is not due to any charges conferred on the gelatin particles by the salts, since the cataphoretic experiments show that salts like NaCl, Na2SO4, or CaCl2, which at the isoelectric point of gelatin increase the solubility of gelatin as well as the stability of suspensions of gelatin-coated collodion particles, leave the particles practically uncharged in the concentrations in which the salts are efficient. 4. It follows from all these facts that the stability of suspensions of gelatin-coated particles in water depends on the solubility of gelatin in water; e.g., on the chemical affinity of certain groups of the gelatin molecule for water. 5. Though crystalline egg albumin is highly soluble in water, the stability of collodion particles coated with crystalline egg albumin does not depend upon the affinity of the albumin molecule for water, but depends practically alone on the electrical double layer surrounding each particle. As soon as the P.D. of this double layer falls below 13 millivolts, the suspension is no longer stable. 6. The critical potential for the stability of suspensions of collodion particles coated with genuine egg albumin is the same as that for particles of boiled (denatured) white of egg. Since through the process of heating, egg albumin loses its solubility in water, it is inferred that egg albumin undergoes the same change when it forms a film around a solid particle like collodion. 7. The influence of electrolytes on the stability of suspensions of collodion particles coated with casein or edestin was similar to that of collodion particles coated with egg albumin. The experiments are, however, complicated by the fact that near the isoelectric point CaCl2 and even NaCl cause a suspension again at concentrations of about M/2 or 1 M, while still higher concentrations may cause a precipitation again. These latter effects have no connection with double layers, but belong probably in the category of solubility phenomena. 8. These experiments permit us to define more definitely the conditions for a general protective action of colloids. Protective colloids must be capable of forming a durable film on the surface of the suspended particles and the molecules constituting the film must have a higher attraction for the molecules of the solvent than for each other; in other words, they must possess true solubility. Only in this case can they prevent the precipitating action of low concentrations of electrolytes on particles which are kept in suspension solely by the high potentials of an electrical double layer. Thus gelatin films, in which the attraction of the molecules for water is preserved, have a general protective action, while crystalline egg albumin, casein, and edestin, which seem to lose their attraction for water when forming a film, have a protective action only under limited conditions stated in the paper.

Enzyme Immobilization Behavior on the Surface of Hydroxyapatite Capsules under Alkaline Condition

2018 ◽  
Vol 782 ◽  
pp. 21-26
Author(s):  
Takeshi Yabutsuka ◽  
Masaya Yamamoto ◽  
Shigeomi Takai ◽  
Takeshi Yao
Keyword(s):  
Enzyme Immobilization ◽  
Double Layer ◽  
Isoelectric Point ◽  
Electrical Double Layer ◽  
Alkaline Condition ◽  
Bicarbonate Buffer

We prepared hydroxyapatite (HA) capsules encapsulating maghemite particles. In order to evaluate enzyme immobilization behavior of the HA capsules under alkaline condition, we immobilized five kinds of enzymes with different isoelectric point in carbonate/bicarbonate buffer (CBB, pH 10.0). When the enzymes in CBB were moderately charged, immobilization efficiency on the HA capsules showed the highest value. It was suggested that immobilization efficiency was affected according to both pI of enzyme and pH of the surrounding solution and that enzyme immobilized on the HA capsules by not only electrical double layer interactions but also ion interaction and other interactions.

scholarly journals Modeling the AC Electrokinetic Behavior of Semiconducting Spheres

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 100 ◽  
Author(s):  
Pablo García-Sánchez ◽  
Jose Flores-Mena ◽  
Antonio Ramos
Keyword(s):  
Double Layer ◽  
First Principles ◽  
Electrical Double Layer ◽  
Aqueous Electrolyte ◽  
Interfacial Phenomena ◽  
Double Layers ◽  
Electrical Double Layers ◽  
Model Predictions ◽  
Doped Silicon ◽  
Arbitrary Thickness

We study theoretically the dielectrophoresis and electrorotation of a semiconducting microsphere immersed in an aqueous electrolyte. To this end, the particle polarizability is calculated from first principles for arbitrary thickness of the Debye layers in liquid and semiconductor. We show that the polarizability dispersion arises from the combination of two relaxation interfacial phenomena: charging of the electrical double layer and the Maxwell–Wagner relaxation. We also calculate the particle polarizability in the limit of thin electrical double layers, which greatly simplifies the analytical calculations. Finally, we show the model predictions for two relevant materials (ZnO and doped silicon) and discuss the limits of validity of the thin double layer approximation.

Marginal stability and critical thickness of strong double layers

1981 ◽  
Vol 26 (2) ◽  
pp. 317-331 ◽  
Author(s):  
Christer Wahlberg
Keyword(s):  
Double Layer ◽  
Critical Thickness ◽  
Double Layers ◽  
Marginal Stability ◽  
Electron Configuration ◽  
The Stability

Previous investigations of the stability, in particular the critical thickness for marginal stability, of an electron configuration of double-layer type are extended in order to include effects of (i) unequal plasma densities in the field-free regions, and (ii) finite values of the parameter eΔø/kTe. The results obtained are compared with the corresponding quantities in various experiments, and a striking coincidence is found.

scholarly journals Smokes: Part I.—A study of their behaviour and a method of determining the number of particles they contain

1923 ◽  
Vol 102 (718) ◽  
pp. 600-615 ◽  
Keyword(s):  
Protective Action ◽  
Colloidal Suspensions ◽  
Point Of View ◽  
Solid Particles ◽  
Electronic Charge ◽  
Colloidal Systems ◽  
Liquid Systems ◽  
The Stability ◽  
The Many ◽  
Liquid States

Theoretically, at least, systems of solid particles of ultra-microscopic size suspended in a gaseous medium, should show many resemblances to those analogous systems in which the dispersion medium is a liquid. It might be expected that the well-known characteristics of colloidal matter, such as coagulation, peptisation, protective action, gel formation, etc., would have their counterpart in the simpler gaseous systems. Should this prove to be the case much information should accrue from a study of these aerosols in which many complicating factors are absent. Now although the movement of individual particles (not necessarily of ultra-microscopic size), suspended in gases, has been investigated very carefully, and the study has led to experimental and theoretical results of the greatest importance, for instance, the measurement of the unit electronic charge (de Broglie (1), Ehrenhaft (2), Millikan (3)), little attention has been paid to the question of the stability of gaseous systems and the changes they undergo, and no attempt has been made to compare the properties of solid colloidal suspensions in the gaseous and liquid states. From this point of view, dusts, fumes, smokes, and clouds are colloidal systems possessing varying degrees of stability, dispersion, and concentration, which sometimes flocculate or precipitate rapidly, sometimes remain highly disperse for long periods of time, and correspond to the many types of liquid systems which vary from coarse suspensions to fine-textured sols.

Bulk stresses due to deformation of the electrical double layer around a charged sphere

1978 ◽  
Vol 85 (4) ◽  
pp. 673-683 ◽  
Author(s):  
William B. Russel
Keyword(s):  
Shear Flow ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Extensional Flow ◽  
Structural Deformation ◽  
Double Layers ◽  
Surface Charges ◽  
Small Surface ◽  
Bulk Stress ◽  
Diffuse Part

A charged particle suspended in an electrolyte solution attracts ions of opposite charge and repels those of like charge. The surface charge and the resulting distributed charge in the fluid comprise an electrical double layer. When a shear flow deforms the diffuse part of the double layer from equilibrium, stresses are generated which make the effective viscosity of the suspension greater than it would be if there were no charges present. In this paper these stresses are calculated for a dilute dispersion of spheres which have small surface charges and which are surrounded by thin double layers. The viscosity is predicted to be Newtonian in extensional flow but shear-thinning with non-zero normal-stress differences in shear flow. For more complex flows a constitutive equation couples the bulk stress directly to the micro-structural deformation responsible for non-Newtonian effects.

scholarly journals Electro-osmosis in kaolinite with pH-dependent surface charge modelling by homogenization

2010 ◽  
Vol 82 (1) ◽  
pp. 223-242 ◽  
Author(s):  
Sidarta A. Lima ◽  
Marcio A. Murad ◽  
Christian Moyne ◽  
Didier Stemmelen
Keyword(s):  
Boundary Condition ◽  
Double Layer ◽  
Slip Boundary Condition ◽  
Solid Particles ◽  
Constitutive Law ◽  
Scale Model ◽  
Double Layers ◽  
Slip Boundary ◽  
Monovalent Ions ◽  
Ph Dependent

A new three-scale model to describe the coupling between pH-dependent flows and transient ion transport, including adsorption phenomena in kaolinite clays, is proposed. The kaolinite is characterized by three separate nano/micro and macroscopic length scales. The pore (micro)-scale is characterized by micro-pores saturated by an aqueous solution containing four monovalent ions and charged solid particles surrounded by thin electrical double layers. The movement of the ions is governed by the Nernst-Planck equations, and the influence of the double layers upon the flow is dictated by the Helmholtz-Smoluchowski slip boundary condition on the tangential velocity. In addition, an adsorption interface condition for the Na+ transportis postulated to capture its retention in the electrical double layer. Thetwo-scalenano/micro model including salt adsorption and slip boundary condition is homogenized to the Darcy scale and leads to the derivation of macroscopic governing equations. One of the notable features of the three-scale model is there construction of the constitutive law of effective partition coefficient that governs the sodium adsorption in the double layer. To illustrate the feasibility of the three-scale model in simulating soil decontamination by electrokinetics, the macroscopic model is discretized by the finite volume method and the desalination of a kaolinite sample by electrokinetics is simulated.

scholarly journals Strong Double Layers, Existence Criteria, and Annihilation: An Application to Solar Flares

1994 ◽  
Vol 142 ◽  
pp. 589-593
Author(s):  
Martin Volwerk ◽  
Jan Kuijpers
Keyword(s):  
Double Layer ◽  
Plasma Heating ◽  
Life Time ◽  
Double Layers ◽  
Type I ◽  
Langmuir Waves ◽  
Direct Emission ◽  
Relativistic Regime ◽  
The Stability ◽  
Existence Criteria

AbstractWe present some conditions for the stability of a strong double layer in a warm, current-carrying plasma, which can be extended into the relativistic regime. We apply a model for plasma heating by the electron beam emitted from the double layer and show that this leads to a finite life time of the double layer. We also show that the radio emission accompanying this process can well describe the observed phenomena in Type I radio bursts using a direct emission mechanism, not involving Langmuir waves.Subject headings: plasmas — Sun: flares — Sun: radio radiation

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