Colloids have particle sizes between 1 nm and 1000 nm. They are classified as lyophilic, lyophobic, or association colloids based on particle interactions with the dispersion medium. Lyophilic colloids readily disperse in the medium, lyophobic colloids resist dispersion, and association colloids form micelles above a critical concentration. Colloids demonstrate optical properties like Tyndall effect, kinetic properties like Brownian motion and diffusion, and electric properties due to particle charge. Their stability depends on preventing particle aggregation.
Dispersed systems consist of particulate matter dispersed in a continuous medium and are classified based on particle size as molecular dispersions, colloidal dispersions, or coarse dispersions. Colloidal dispersions have particle sizes between 1-1000 nm that are not visible under an ordinary microscope but can be seen under an electron microscope. Colloidal dispersions exhibit Brownian motion, diffusion, sedimentation, osmotic pressure, viscosity, and optical properties. The document then provides details on these various properties of colloidal dispersions.
Classification of dispersed systems & their general characteristics, size & shapes of colloidal particles, classification of colloids & comparative account of their general properties. Optical, kinetic & electrical properties. Effect of electrolytes, coacervation, peptization& protective action.
Colloids have particle sizes between 1 nm and 1000 nm. They are classified as lyophilic, lyophobic, or association colloids based on particle interactions with the dispersion medium. Lyophilic colloids readily disperse in the medium while lyophobic colloids do not. Association colloids form micelles above a critical micelle concentration. Colloids demonstrate optical properties like Tyndall effect and can be imaged with electron microscopes. They also exhibit kinetic properties including Brownian motion, diffusion, osmotic pressure, and sedimentation. Colloidal particles are often electrically charged, leading to electrokinetic phenomena like electrophoresis and electroosmosis. Stability is important for preventing
This document provides an overview of suspensions, including their classification, properties, formulation, and stability. Key points include:
- Suspensions are heterogeneous systems with an insoluble dispersed phase distributed throughout a continuous phase. They can be classified based on their intended use, concentration of solids, particle size, and electrokinetic properties.
- Interfacial properties like surface tension affect particle flocculation and sedimentation. Surfactants can reduce surface tension to promote deflocculation.
- Particle size, concentration, and Brownian motion influence sedimentation rates. Flocculated particles settle faster but are easier to redisperse than deflocculated particles.
- Stable suspensions are formulated using vehicles to
Colloids have many important applications in pharmaceuticals, food, and industry. Pharmaceutical applications include using colloids for drug delivery and therapy, as well as coating tablets for protection and controlled release. Colloids are also important in food products like milk, butter, and ice cream. Industrial uses involve non-drip paints, sewage treatment, clarifying water, and in artificial kidney machines.
This document discusses suspensions, which are two-phase systems consisting of finely divided solid particles dispersed in a liquid vehicle. Suspensions can be classified based on administration route or particle size. They are useful for drugs with low solubility and can improve stability, release properties, and bioavailability compared to other dosage forms. However, suspensions are also prone to physical instability issues like sedimentation. The document outlines factors that affect sedimentation and strategies to improve suspension stability such as controlling particle size, viscosity, surface charge, and use of surfactants or flocculating agents. Wetting agents are also discussed which help disperse solid particles in the liquid vehicle by reducing surface tension.
This document discusses an introduction to rheology and its importance in pharmacy. It begins by outlining the topics to be covered, which include the importance of rheology in pharmacy applications, definitions and fundamentals, types of fluids, viscosity, measurements of viscosity, instrumentation, and viscoelasticity. The first section defines rheology and describes its importance in areas like manufacturing dosage forms, handling drugs for administration, topical applications, and more. The introduction provides definitions of key terms like shear stress and rate of shear. It also describes Newton's laws of viscous flow. The document goes on to classify fluids as Newtonian or non-Newtonian and describes different types of non-Newtonian fluids.
Thixotropy is defined as the property of a viscous material to become less viscous when agitated or disturbed and then regain its original viscosity over time when left undisturbed. Thixotropic materials undergo a reversible structural transition from a gel state to a sol state when subjected to shear forces, and back to a gel again when at rest. Characterization of thixotropy involves measuring the decrease in viscosity under applied shear stress and subsequent gradual recovery when stress is removed. Common thixotropic materials include ointments, pastes, putties, and clays.
Dispersed systems consist of particulate matter dispersed in a continuous medium and are classified based on particle size as molecular dispersions, colloidal dispersions, or coarse dispersions. Colloidal dispersions have particle sizes between 1-1000 nm that are not visible under an ordinary microscope but can be seen under an electron microscope. Colloidal dispersions exhibit Brownian motion, diffusion, sedimentation, osmotic pressure, viscosity, and optical properties. The document then provides details on these various properties of colloidal dispersions.
Classification of dispersed systems & their general characteristics, size & shapes of colloidal particles, classification of colloids & comparative account of their general properties. Optical, kinetic & electrical properties. Effect of electrolytes, coacervation, peptization& protective action.
Colloids have particle sizes between 1 nm and 1000 nm. They are classified as lyophilic, lyophobic, or association colloids based on particle interactions with the dispersion medium. Lyophilic colloids readily disperse in the medium while lyophobic colloids do not. Association colloids form micelles above a critical micelle concentration. Colloids demonstrate optical properties like Tyndall effect and can be imaged with electron microscopes. They also exhibit kinetic properties including Brownian motion, diffusion, osmotic pressure, and sedimentation. Colloidal particles are often electrically charged, leading to electrokinetic phenomena like electrophoresis and electroosmosis. Stability is important for preventing
This document provides an overview of suspensions, including their classification, properties, formulation, and stability. Key points include:
- Suspensions are heterogeneous systems with an insoluble dispersed phase distributed throughout a continuous phase. They can be classified based on their intended use, concentration of solids, particle size, and electrokinetic properties.
- Interfacial properties like surface tension affect particle flocculation and sedimentation. Surfactants can reduce surface tension to promote deflocculation.
- Particle size, concentration, and Brownian motion influence sedimentation rates. Flocculated particles settle faster but are easier to redisperse than deflocculated particles.
- Stable suspensions are formulated using vehicles to
Colloids have many important applications in pharmaceuticals, food, and industry. Pharmaceutical applications include using colloids for drug delivery and therapy, as well as coating tablets for protection and controlled release. Colloids are also important in food products like milk, butter, and ice cream. Industrial uses involve non-drip paints, sewage treatment, clarifying water, and in artificial kidney machines.
This document discusses suspensions, which are two-phase systems consisting of finely divided solid particles dispersed in a liquid vehicle. Suspensions can be classified based on administration route or particle size. They are useful for drugs with low solubility and can improve stability, release properties, and bioavailability compared to other dosage forms. However, suspensions are also prone to physical instability issues like sedimentation. The document outlines factors that affect sedimentation and strategies to improve suspension stability such as controlling particle size, viscosity, surface charge, and use of surfactants or flocculating agents. Wetting agents are also discussed which help disperse solid particles in the liquid vehicle by reducing surface tension.
This document discusses an introduction to rheology and its importance in pharmacy. It begins by outlining the topics to be covered, which include the importance of rheology in pharmacy applications, definitions and fundamentals, types of fluids, viscosity, measurements of viscosity, instrumentation, and viscoelasticity. The first section defines rheology and describes its importance in areas like manufacturing dosage forms, handling drugs for administration, topical applications, and more. The introduction provides definitions of key terms like shear stress and rate of shear. It also describes Newton's laws of viscous flow. The document goes on to classify fluids as Newtonian or non-Newtonian and describes different types of non-Newtonian fluids.
Thixotropy is defined as the property of a viscous material to become less viscous when agitated or disturbed and then regain its original viscosity over time when left undisturbed. Thixotropic materials undergo a reversible structural transition from a gel state to a sol state when subjected to shear forces, and back to a gel again when at rest. Characterization of thixotropy involves measuring the decrease in viscosity under applied shear stress and subsequent gradual recovery when stress is removed. Common thixotropic materials include ointments, pastes, putties, and clays.
This document discusses colloidal dispersions and their properties. It defines colloidal dispersions as heterogeneous biphasic systems with dispersed particles in the nano size range of 1-1000 nm. Colloids can be classified as lyophilic, lyophobic, or association colloids based on particle-solvent interactions. Key optical properties of colloids include the Tyndall effect, light scattering measurements to determine particle size and molecular weight, and imaging with electron microscopes. Colloids also exhibit kinetic properties like Brownian motion, diffusion, osmotic pressure, and sedimentation rates related to particle size. Electrolytes can cause coagulation or precipitation of colloids according to the Schulze-
Rheology is the science describing the flow and deformation of matter under stress. Viscosity describes a fluid's resistance to flow and is dependent on factors like temperature, pressure, and shear rate. Newtonian fluids have a constant viscosity regardless of shear rate, while non-Newtonian fluids have variable viscosity. Common non-Newtonian behaviors include plastic flow, pseudoplastic (shear-thinning) flow, and dilatant (shear-thickening) flow. Thixotropy is time-dependent shear thinning where viscosity decreases under shear and recovers with time. Viscometers like capillary, falling ball, and rotational viscometers are used to measure viscosity. Rheology is important in formulation development
This document discusses disperse systems and colloids. It defines a disperse system as a substance dispersed in discrete units throughout another substance, with each phase existing in solid, liquid, or gaseous states. Colloids have large surface areas compared to larger particles due to their small size. Their shape and purification through dialysis and electrodialysis are also discussed. Finally, applications of colloidal solutions in therapy, stability, absorption, targeted drug delivery, photography, and blood clotting are outlined.
Multiple emulsions are complex systems that contain both water-in-oil (W/O) and oil-in-water (O/W) emulsions. They are thermodynamically unstable and require a combination of hydrophilic and hydrophobic surfactants to stabilize them. Common types include W/O/W and O/W/O emulsions. Multiple emulsions can prolong the release of active ingredients and have applications in controlled drug delivery, targeted delivery, and more. They are prepared using techniques like solvent evaporation or double emulsification and provide a novel carrier system for drugs, cosmetics, and other agents.
This document provides an overview of microemulsions and multiple emulsions. It defines microemulsions as thermodynamically stable, optically isotropic and clear dispersions of oil and water stabilized by an amphiphile. Three types of microemulsions are described: oil-in-water, water-in-oil, and bi-continuous. Preparation methods and characterization of microemulsions are also outlined. Multiple emulsions involve a second level of emulsification, forming either oil-in-water-in-oil or water-in-oil-in-water dispersions. Common preparation techniques for multiple emulsions include two-step emulsification and phase inversion methods.
Dispersion system
suspensions
interfacial properties of suspensions
zeta potential
Sedimentation parameters
Settling in suspension
Formulation of suspension
Preparation of suspension
The document summarizes key information about pharmaceutical suspensions. It defines suspensions as coarse dispersions of insoluble solids suspended in a liquid medium. Suspensions consist of two phases, with the internal solid phase dispersed throughout the external liquid phase using mechanical agitation and excipients. Suspensions are advantageous for stable delivery of drugs that are insoluble or unstable in solution. The document outlines factors that influence sedimentation of particles in suspensions and methods for achieving physical stability, including controlling particle size and flocculation.
Colloids have many applications in pharmaceuticals as therapeutic agents, drug delivery systems, and in coating and protecting solid dosages. They also occur naturally in proteins, tissues, and plant materials. Colloids play an important role in conventional water treatment processes like coagulation and flocculation to remove small particles and purify water. They are used in food products to form gels, emulsions, foams, and other colloidal structures. Colloids are important components of paints, inks, and other materials where they carry pigments and bind substances together.
The document discusses four methods of dispersion for preparing colloids: 1) Mechanical dispersion uses grinding to break large particles into smaller colloidal particles, 2) Electrical dispersion applies an electric arc to vaporize and disperse metal particles, 3) Peptization dispersion converts a precipitate into a colloidal sol using an electrolyte, and 4) Homogenization emulsifies substances like milk or cream to form a stable colloid.
The document discusses coarse dispersions and suspensions. It defines a suspension as an insoluble solid dispersed in a liquid medium where the particles are larger than 0.1 μm. Common types of suspensions include orally administered, ophthalmic, and injectable suspensions. Desirable qualities include minimal settling, uniform distribution, and appropriate viscosity. The document outlines factors that influence particle interactions like surface energy and interfacial tension. It also discusses strategies to achieve stability including controlled flocculation, use of surfactants, polymers, and structured vehicles.
This document discusses different methods for purifying colloidal dispersions, including dialysis, electrodialysis, and ultrafiltration. Dialysis involves diffusing low molecular weight impurities out of a colloidal solution through a semi-permeable membrane. Electrodialysis enhances this diffusion process by applying an electric potential. Ultrafiltration uses an ultrafilter membrane with small pores to retain colloidal particles while filtering out smaller solutes under pressure.
This document summarizes a seminar on colloidal dispersions presented by Sayani Saha. It defines colloidal dispersions as systems with a dispersed particle phase and continuous dispersion medium between 1-1000 nm. Dispersions are classified by size as molecular, colloidal, or coarse dispersions. The properties of colloidal sols are discussed, including how they are lyophilic or lyophobic, how particles are solvated, how they are prepared, and how they are affected by electrolytes. Various shapes of colloidal particles and classifications based on dispersion medium and phase are also summarized. The document concludes with brief discussions of coacervation and peptization processes.
Sensitization and protective colloidal actionVarshaBarethiya
Lyophobic dispersions are unstable in the presence of electrolytes due to the neutralization of particle charges. Sensitization can occur when a small amount of hydrophilic colloid is added, making the hydrophobic sol more sensitive to precipitation from electrolytes through adsorption of oppositely charged particles. Protective colloidal action results from the adsorption of a large amount of hydrophilic colloids carrying opposite charges onto hydrophobic particles, forming a protective layer that prevents coagulation by ions. Colloids that stabilize other colloids through this process are called protective colloids.
The document discusses colloids and their properties. It defines colloids as dispersed systems with particle sizes between 1-1000 nm. Colloids can be lyophilic, lyophobic, or association colloids depending on interactions between particles and dispersion medium. Key properties of colloids include optical effects like Tyndall scattering, Brownian motion, diffusion, osmotic pressure, and electrokinetic phenomena that are influenced by particle size, temperature, and viscosity. Colloids find applications in pharmaceuticals for solubilization, increasing bioavailability, and as therapeutic or diagnostic agents.
R. VIJAYAKUMAR., M Pharm,
Research Scholar
department of Pharmaceutical Technology.
Anna university- BIT
Tiruchirappalli
B Pharm / 2nd Year ,III Semester.
UNIT-I / Colloidal dispersion's
A coordination complex is formed via a Lewis acid-base reaction between a central metal ion and surrounding ligands. Common ligands donate lone electron pairs to form coordinate covalent bonds with the metal. Coordination complexes have altered physical and chemical properties compared to the individual components. Complexation can impact drug properties like solubility, stability, and pharmacokinetics, which are important considerations in drug delivery and activity.
1. The document discusses colloidal dispersions, which are systems where particles between 1 nm and 1000 nm are dispersed uniformly throughout a dispersion medium.
2. Colloidal systems are classified based on particle size into molecular dispersions, colloidal dispersions, and coarse dispersions. They are also classified based on particle-medium interactions into lyophilic, lyophobic, and association colloids.
3. The key properties of colloidal systems discussed are electrical properties (surface charge, zeta potential, electrophoresis), optical properties (Tyndall effect, turbidity), and kinetic properties (Brownian motion, diffusion, viscosity).
This document discusses surface and interfacial phenomena. It defines interfaces and divides them into solid and liquid interfaces. Liquid interfaces deal with liquid-gas or liquid-liquid phases and have applications in infiltration, biopharmaceuticals, and suspensions/emulsions. Surface tension exists between solid-gas and liquid-gas phases, while interfacial tension exists between immiscible liquids. Various methods are described to measure surface tension, interfacial tension, and surface free energy. Surfactants are also discussed, including how they lower tensions and are used in products. Adsorption at interfaces and isotherms are briefly covered.
This document discusses emulsions. It defines an emulsion as a dispersion of small globules of one liquid distributed throughout another immiscible liquid. Emulsions are classified based on the dispersed phase as oil-in-water or water-in-oil, and based on droplet size as macroemulsions or microemulsions. Emulsifying agents are substances that stabilize emulsions by forming films at the liquid interfaces. Various natural, semi-synthetic, and synthetic agents are described. Methods for preparing emulsions include dry gum, wet gum, and bottle methods. Factors that cause emulsion instability like cracking and creaming are also outlined.
This document discusses colloids and their properties. It defines colloids as dispersed systems with particle sizes between 1 nm and 1000 nm. Colloids have large surface areas and include systems like sols, emulsions, and foams. They are classified as lyophilic, lyophobic, or association colloids based on particle interactions. Common preparation methods are milling, peptization, and condensation. Colloids exhibit optical properties like Tyndall effect and can be viewed under electron microscopes. They have applications in therapy, stability, absorption, and targeted drug delivery due to their unique size.
1. A colloid is a mixture of one substance dispersed evenly throughout another substance where at least one dimension of the dispersed particles is between 1-1000 nanometers.
2. Colloids can be classified as lyophilic or lyophobic depending on whether the dispersed particles are attracted to or repel the dispersion medium.
3. Common methods for preparing lyophobic colloids include mechanical dispersion, arc discharge, and chemical reactions like reduction or hydrolysis, while lyophilic colloids are often prepared by simple mixing.
This document discusses colloidal dispersions and their properties. It defines colloidal dispersions as heterogeneous biphasic systems with dispersed particles in the nano size range of 1-1000 nm. Colloids can be classified as lyophilic, lyophobic, or association colloids based on particle-solvent interactions. Key optical properties of colloids include the Tyndall effect, light scattering measurements to determine particle size and molecular weight, and imaging with electron microscopes. Colloids also exhibit kinetic properties like Brownian motion, diffusion, osmotic pressure, and sedimentation rates related to particle size. Electrolytes can cause coagulation or precipitation of colloids according to the Schulze-
Rheology is the science describing the flow and deformation of matter under stress. Viscosity describes a fluid's resistance to flow and is dependent on factors like temperature, pressure, and shear rate. Newtonian fluids have a constant viscosity regardless of shear rate, while non-Newtonian fluids have variable viscosity. Common non-Newtonian behaviors include plastic flow, pseudoplastic (shear-thinning) flow, and dilatant (shear-thickening) flow. Thixotropy is time-dependent shear thinning where viscosity decreases under shear and recovers with time. Viscometers like capillary, falling ball, and rotational viscometers are used to measure viscosity. Rheology is important in formulation development
This document discusses disperse systems and colloids. It defines a disperse system as a substance dispersed in discrete units throughout another substance, with each phase existing in solid, liquid, or gaseous states. Colloids have large surface areas compared to larger particles due to their small size. Their shape and purification through dialysis and electrodialysis are also discussed. Finally, applications of colloidal solutions in therapy, stability, absorption, targeted drug delivery, photography, and blood clotting are outlined.
Multiple emulsions are complex systems that contain both water-in-oil (W/O) and oil-in-water (O/W) emulsions. They are thermodynamically unstable and require a combination of hydrophilic and hydrophobic surfactants to stabilize them. Common types include W/O/W and O/W/O emulsions. Multiple emulsions can prolong the release of active ingredients and have applications in controlled drug delivery, targeted delivery, and more. They are prepared using techniques like solvent evaporation or double emulsification and provide a novel carrier system for drugs, cosmetics, and other agents.
This document provides an overview of microemulsions and multiple emulsions. It defines microemulsions as thermodynamically stable, optically isotropic and clear dispersions of oil and water stabilized by an amphiphile. Three types of microemulsions are described: oil-in-water, water-in-oil, and bi-continuous. Preparation methods and characterization of microemulsions are also outlined. Multiple emulsions involve a second level of emulsification, forming either oil-in-water-in-oil or water-in-oil-in-water dispersions. Common preparation techniques for multiple emulsions include two-step emulsification and phase inversion methods.
Dispersion system
suspensions
interfacial properties of suspensions
zeta potential
Sedimentation parameters
Settling in suspension
Formulation of suspension
Preparation of suspension
The document summarizes key information about pharmaceutical suspensions. It defines suspensions as coarse dispersions of insoluble solids suspended in a liquid medium. Suspensions consist of two phases, with the internal solid phase dispersed throughout the external liquid phase using mechanical agitation and excipients. Suspensions are advantageous for stable delivery of drugs that are insoluble or unstable in solution. The document outlines factors that influence sedimentation of particles in suspensions and methods for achieving physical stability, including controlling particle size and flocculation.
Colloids have many applications in pharmaceuticals as therapeutic agents, drug delivery systems, and in coating and protecting solid dosages. They also occur naturally in proteins, tissues, and plant materials. Colloids play an important role in conventional water treatment processes like coagulation and flocculation to remove small particles and purify water. They are used in food products to form gels, emulsions, foams, and other colloidal structures. Colloids are important components of paints, inks, and other materials where they carry pigments and bind substances together.
The document discusses four methods of dispersion for preparing colloids: 1) Mechanical dispersion uses grinding to break large particles into smaller colloidal particles, 2) Electrical dispersion applies an electric arc to vaporize and disperse metal particles, 3) Peptization dispersion converts a precipitate into a colloidal sol using an electrolyte, and 4) Homogenization emulsifies substances like milk or cream to form a stable colloid.
The document discusses coarse dispersions and suspensions. It defines a suspension as an insoluble solid dispersed in a liquid medium where the particles are larger than 0.1 μm. Common types of suspensions include orally administered, ophthalmic, and injectable suspensions. Desirable qualities include minimal settling, uniform distribution, and appropriate viscosity. The document outlines factors that influence particle interactions like surface energy and interfacial tension. It also discusses strategies to achieve stability including controlled flocculation, use of surfactants, polymers, and structured vehicles.
This document discusses different methods for purifying colloidal dispersions, including dialysis, electrodialysis, and ultrafiltration. Dialysis involves diffusing low molecular weight impurities out of a colloidal solution through a semi-permeable membrane. Electrodialysis enhances this diffusion process by applying an electric potential. Ultrafiltration uses an ultrafilter membrane with small pores to retain colloidal particles while filtering out smaller solutes under pressure.
This document summarizes a seminar on colloidal dispersions presented by Sayani Saha. It defines colloidal dispersions as systems with a dispersed particle phase and continuous dispersion medium between 1-1000 nm. Dispersions are classified by size as molecular, colloidal, or coarse dispersions. The properties of colloidal sols are discussed, including how they are lyophilic or lyophobic, how particles are solvated, how they are prepared, and how they are affected by electrolytes. Various shapes of colloidal particles and classifications based on dispersion medium and phase are also summarized. The document concludes with brief discussions of coacervation and peptization processes.
Sensitization and protective colloidal actionVarshaBarethiya
Lyophobic dispersions are unstable in the presence of electrolytes due to the neutralization of particle charges. Sensitization can occur when a small amount of hydrophilic colloid is added, making the hydrophobic sol more sensitive to precipitation from electrolytes through adsorption of oppositely charged particles. Protective colloidal action results from the adsorption of a large amount of hydrophilic colloids carrying opposite charges onto hydrophobic particles, forming a protective layer that prevents coagulation by ions. Colloids that stabilize other colloids through this process are called protective colloids.
The document discusses colloids and their properties. It defines colloids as dispersed systems with particle sizes between 1-1000 nm. Colloids can be lyophilic, lyophobic, or association colloids depending on interactions between particles and dispersion medium. Key properties of colloids include optical effects like Tyndall scattering, Brownian motion, diffusion, osmotic pressure, and electrokinetic phenomena that are influenced by particle size, temperature, and viscosity. Colloids find applications in pharmaceuticals for solubilization, increasing bioavailability, and as therapeutic or diagnostic agents.
R. VIJAYAKUMAR., M Pharm,
Research Scholar
department of Pharmaceutical Technology.
Anna university- BIT
Tiruchirappalli
B Pharm / 2nd Year ,III Semester.
UNIT-I / Colloidal dispersion's
A coordination complex is formed via a Lewis acid-base reaction between a central metal ion and surrounding ligands. Common ligands donate lone electron pairs to form coordinate covalent bonds with the metal. Coordination complexes have altered physical and chemical properties compared to the individual components. Complexation can impact drug properties like solubility, stability, and pharmacokinetics, which are important considerations in drug delivery and activity.
1. The document discusses colloidal dispersions, which are systems where particles between 1 nm and 1000 nm are dispersed uniformly throughout a dispersion medium.
2. Colloidal systems are classified based on particle size into molecular dispersions, colloidal dispersions, and coarse dispersions. They are also classified based on particle-medium interactions into lyophilic, lyophobic, and association colloids.
3. The key properties of colloidal systems discussed are electrical properties (surface charge, zeta potential, electrophoresis), optical properties (Tyndall effect, turbidity), and kinetic properties (Brownian motion, diffusion, viscosity).
This document discusses surface and interfacial phenomena. It defines interfaces and divides them into solid and liquid interfaces. Liquid interfaces deal with liquid-gas or liquid-liquid phases and have applications in infiltration, biopharmaceuticals, and suspensions/emulsions. Surface tension exists between solid-gas and liquid-gas phases, while interfacial tension exists between immiscible liquids. Various methods are described to measure surface tension, interfacial tension, and surface free energy. Surfactants are also discussed, including how they lower tensions and are used in products. Adsorption at interfaces and isotherms are briefly covered.
This document discusses emulsions. It defines an emulsion as a dispersion of small globules of one liquid distributed throughout another immiscible liquid. Emulsions are classified based on the dispersed phase as oil-in-water or water-in-oil, and based on droplet size as macroemulsions or microemulsions. Emulsifying agents are substances that stabilize emulsions by forming films at the liquid interfaces. Various natural, semi-synthetic, and synthetic agents are described. Methods for preparing emulsions include dry gum, wet gum, and bottle methods. Factors that cause emulsion instability like cracking and creaming are also outlined.
This document discusses colloids and their properties. It defines colloids as dispersed systems with particle sizes between 1 nm and 1000 nm. Colloids have large surface areas and include systems like sols, emulsions, and foams. They are classified as lyophilic, lyophobic, or association colloids based on particle interactions. Common preparation methods are milling, peptization, and condensation. Colloids exhibit optical properties like Tyndall effect and can be viewed under electron microscopes. They have applications in therapy, stability, absorption, and targeted drug delivery due to their unique size.
1. A colloid is a mixture of one substance dispersed evenly throughout another substance where at least one dimension of the dispersed particles is between 1-1000 nanometers.
2. Colloids can be classified as lyophilic or lyophobic depending on whether the dispersed particles are attracted to or repel the dispersion medium.
3. Common methods for preparing lyophobic colloids include mechanical dispersion, arc discharge, and chemical reactions like reduction or hydrolysis, while lyophilic colloids are often prepared by simple mixing.
Colloids are mixtures where one substance is microscopically dispersed throughout another. They consist of two phases - a dispersed phase made of very tiny particles 1nm to 1um in size suspended in a continuous dispersion medium. Common examples are milk, fog, and blood. Colloids can be classified based on the physical state of the phases and the interactions between them. Preparation methods include mechanical grinding, electrical dispersion, peptization of precipitates, and condensation by changes in conditions. The interactions between colloidal particles, such as excluded volume repulsion, electrostatic forces, van der Waals forces, and steric effects influence colloid stability and properties.
The document discusses colloidal dispersions, which are systems with particulate matter dispersed in a continuous medium. Colloidal dispersions have particle sizes between 1-500 nm. They are classified as lyophilic, lyophobic, or association colloids based on particle interactions. Lyophilic colloids are stable and interact with the solvent, while lyophobic colloids are less stable and do not interact well with water. Association colloids form micelles above a critical concentration of amphiphilic molecules. Colloids have various properties related to their kinetics, optics, and electrical characteristics that depend on factors like particle size, shape, and surface charge.
Colloids are substances microscopically dispersed throughout another substance. The dispersed particles range in size from 1-100 nm. Colloids exhibit properties between true solutions and suspensions due to their intermediate particle size. They are able to pass through filters but not semipermeable membranes. Common examples include milk, fog, mayonnaise and paints. Colloids can be classified based on factors like the physical state of the phases, the interaction between the phases, the size and nature of dispersed particles, and the electrical charge on particles. They are purified using techniques like dialysis, electrodialysis, and ultrafiltration which separate colloidal particles from dissolved substances.
Colloids can be classified based on particle size as molecular, colloidal, or coarse dispersions. Colloidal dispersions have particle sizes between 1-500 nm. Colloids can also be classified as lyophilic, lyophobic, or association colloids based on particle interactions. Lyophilic particles are solvent-loving, lyophobic are solvent-hating, and association colloids form micelles. Purification of colloids can be done using dialysis, which separates colloidal particles from dissolved impurities based on size, or electrodialysis, which uses an electric field to enhance impurity removal.
This document provides information about colloids, including:
1. It defines colloids and distinguishes them from true solutions and suspensions based on particle size and other properties.
2. It describes the phases in a colloidal solution and different classification methods for colloids.
3. It explains various preparation methods for lyophobic colloidal solutions and properties of colloids such as Brownian motion, Tyndall effect, and coagulation.
4. It discusses purification techniques like dialysis and ultrafiltration and industrial applications of colloids.
Colloidal Dispersion, Its Types and Method of PreparationChitralekhaTherkar
Dispersion
Definition of Colloids
Shapes and Sizes of Colloids
Classification of Colloids
Properties of Colloids
1. Optical Properties.
2. Electrical Properties.
3. Kinetic Properties
Purification of Colloids
Method of Preparation of Colloids.
Physical Stability of Colloids.
Factors affecting Colloidal Dispersion.
Colloidal dispersions are heterogeneous systems where one substance is divided into small particles, between 1 nm and 1 μm, dispersed throughout a second substance. They can be classified based on the dispersed and dispersion medium, such as sols where the medium is a liquid. Colloidal particles exhibit properties like Brownian motion, diffusion, and Tyndall effect. Their size, shape, and surface charge affect characteristics like stability, flowability, and pharmacological effects. Purification methods remove electrolytes and impurities through dialysis, ultrafiltration, or electrodialysis.
Colloids are crucial to both ordinary living and pharmacological formulations. the study of both big molecules
and intricately divided multiphase systems is known as colloidal science. the intersection of colloid and
surface science is the multi-phase system. a colloid is a mixture in which one material is suspended within
another substance and has insoluble particles scattered over a tiny scale. between genuine solutions and
suspensions, colloidal solutions or colloidal dispersions represent a middle ground. the dispersed phase of
colloids is distributed throughout the dispersion medium. in many facets of chemistry, colloidal chemistry
knowledge is necessary. this article provides information on what colloids are, their types, sizes, forms,
qualities, and uses.
This document provides an overview of colloids, including:
1) What colloids are and the difference between lyophobic and lyophilic colloids
2) Methods for preparing colloidal solutions, including dispersion and condensation methods
3) Properties of colloidal systems like optical properties related to light scattering and the electrical double layer
Colloids are solutions where the solute particles are between 1-100 nm. They do not settle out spontaneously but can be separated through methods like ultracentrifugation. Colloids are classified as lyophobic or lyophilic based on their affinity for the solvent. Lyophobic colloids have no affinity and are kept separated by charge, while lyophilic colloids have stability from both charge and a solvent layer. Colloids demonstrate properties like Brownian motion, Tyndall effect, and protection by other colloids to prevent precipitation.
Crystalloids are substances smaller than 1 nm that can pass through semipermeable membranes, while colloids are larger substances between 1-100 nm that cannot pass through. Colloids make up 90% of living tissue and include proteins. They differ from crystalloids in their size, ability to pass membranes, osmotic properties, and ability to be dialyzed. Dialysis and filtration are methods to separate crystalloids and colloids based on membrane permeability.
Here almost full every topics interrelated with colloid chemistry has been discussed.The slides have been made showing question pattern taking Begum Rokeya University Chemistry Department previous year questions to appear the slides easy towards the viewers.Stay join with me.Thank you.
1. A colloid is a heterogeneous system with one substance dispersed as very fine particles in another substance. Colloids are classified based on the physical state, interaction between phases, and type of dispersed particles.
2. Common colloids include sols, gels, and emulsions. Soaps form micelles above a critical micelle concentration when hydrocarbon chains aggregate.
3. Colloids can be purified through dialysis, electrodialysis, or ultrafiltration to remove electrolytes and impurities. Colloidal particles exhibit properties like Tyndall effect, Brownian motion, and surface charge.
A colloid is a substance microscopically dispersed throughout another substance.
The word colloid comes from a Greek word 'kolla', which means glue thus colloidal particles are glue like substances.
These particles pass through a filter paper but not through a semipermeable membrane.
Colloids can be made settle by the process of centrifugation.
The document discusses colloids, which are heterogeneous mixtures with dispersed particles between 1-1000 nm. It classifies colloids based on the physical state of the dispersed and continuous phases, the nature of particle-solvent interactions, and the type of dispersed particles. Multimolecular, macromolecular, and associated colloids are described. Methods for preparing lyophobic and lyophilic colloids as well as purifying colloids are outlined. Key properties like Tyndall effect, Brownian motion, and coagulation are also summarized along with applications of colloids.
This document provides an overview of colloids and emulsions. It defines colloids and discusses their classification based on physical state and particle interactions. Methods for preparing and purifying lyophobic and lyophilic colloids are described. Key properties of colloids like Tyndall effect and electrophoresis are summarized. Applications of colloids include rubber plating, sewage disposal, and the cleaning action of soap. Emulsions are defined as liquid-liquid colloids like milk, and the document concludes with thanking the reader.
This document provides information about colloidal dispersions. It defines a colloid as a substance microscopically dispersed throughout another substance, with particle sizes between 1-1000nm. Colloids can be classified based on their physical state, nature of interactions, size, appearance, or electric charge. Key properties of colloids include Brownian motion, diffusion, sedimentation, viscosity, light scattering, and electrical behaviors like electrophoresis and electrosmosis. Colloids find applications in areas like therapy, absorption, solubility, stability, and drug targeting.
This document discusses the classification and preparation of colloidal dispersions. It begins by classifying colloids based on the interaction between the dispersed phase and dispersion medium into lyophilic, lyophobic, and association colloids. Lyophilic colloids have affinity for the dispersion medium, making them thermodynamically stable. Lyophobic colloids require special preparation methods since the dispersed particles are solvent-hating. Association colloids involve micelle formation using surfactants above the critical micelle concentration. The document also describes various methods for preparing and purifying colloidal dispersions, including mechanical grinding, peptization, addition of nonsolvents, and ultrafiltration.
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
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This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
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Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
2. Dispersed Systems:
Dispersed systems consist of particulate matter (dispersed phase),
distributed throughout a continuous phase (dispersion medium).
They are classified according to the particle diameter of the
dispersed material:
1- Molecular dispersions (less than 1 nm)
- Particles invisible in electron microscope
- Pass through semipermeable membranes and filter paper
- Particles do not settle down on standing
- Undergo rapid diffusion
- E.g. ordinary ions, glucose
3. Dispersed Systems:
2- Colloidal dispersions (1 nm - o.5 um)
- Particles not resolved by ordinary microscope, can be detected by
electron microscope.
- Pass through filter paper but not pass through semipermeable
membrane.
- Particles made to settle by centrifugation
- Diffuse very slowly
- E.g. colloidal silver sols, naural and synthetic polymers
3- Coarse dispersions (> 0.5 um)
- Particles are visible under ordinary microscope
- Do not pass through filter paper or semipermeable membrane.
- Particles settle down under gravity
- Do not diffuse
- E.g. emulsions, suspensions, red blood cells
5. Size and shape of colloids:
Particles lying in the colloidal size have large surface
area when compared with the surface area of an equal
volume of larger particles.
Specific surface: the surface area per unit weight or
volume of material.
The possession of large specific surface results in:
1- platinium is effective as catalyst only when found in colloidal form
due to large surface area which adsorb reactant on their surface.
2- The colour of colloidal dispersion is related to the size of the
paticles
e.g. red gold sol takes a blue colour when the particles increase in
size
6. Size and shape of colloids:
- The shape of colloidal particles in dispersion is important:
The more extended the particle the greater its specific
surface the greater the attractive force between the
particles of the dispersed phase and the dispersion
medium.
Flow, sedimentation and osmotic pressure of the colloidal
system affected by the shape of colloidal particles.
Particle shape may also influence the pharmacologic
action.
8. Purification of colloidal
solutions:
When a colloidal solution is prepared is often contains
certain electrolytes which tend to destabilize it. The
following methods are used for purification:
1- Dialysis:
- Semipermeable cellophane
membrane prevent the
passage of colloidal particles,
yet allow the passage of
small molecules or electrolytes.
9. Purification of colloidal
solutions:
2- Electrodialysis:
- In the dialysis unit, the movement of ions across the
membrane can be speeded up by applying an electric
current through the electrodes induced in the solution.
- The most important use of dialysis is the purification of
blood in artificial kidney machines.
- The dialysis membrane allows small particles (ions) to
pass through but the colloidal size particles
(haemoglobin) do not pass through the membrane.
11. Applications of colloidal solutions:
1- Therapy--- Colloidal system are used as therapeutic
agents in different areas.
e.g- Silver colloid-germicidal
Copper colloid-anticancer
Mercury colloid-Antisyphilis
2- Stability---e.g. lyophobic colloids prevent flocculation in
suspensions.
e.g- Colloidal dispersion of gelatin is used in coating over
tablets and granules which upon drying leaves a
uniform dry film over them and protect them from
adverse conditions of the atmosphere.
12. Applications of colloidal solutions:
4- Absorption--- As colloidal dimensions are small
enough, they have a huge surface area. Hence, the
drug constituted colloidal form is released in large
amount.
e.g- sulphur colloid gives a large quantity of sulphur and
this often leads to sulphur toxicity
5-Targeted Drug Delivery--- Liposomes are of colloidal
dimensions and are preferentially taken up by the liver
and spleen.
13. Applications of colloidal solutions:
6- Photography:
A colloidal solution of silver bromide in gelatine is applied
on glass plates or celluloid films to form sensitive plates
in photography.
7- Clotting of blood:
- Blood is a colloidal solution and is negatively charged.
- On applying a solution of Fecl3 bleeding stops and blood
clotting occurs as Fe+3
ions neutralize the ion charges on
the colloidal particles.
14. Types of colloids
Colloids are usually classified according to:
1- The original states of their constituent parts
15. Types of colloids:
2-The nature of interaction between dispersed phase and
dispersion medium.
A-Lyophilic colloids (solvent attracting) (solvent
loving) – The particles in a lyophilic system have a
great affinity for the solvent.
If water is the dispersing medium, it is often known as a
hydrosol or hydrophilic.
readily solvated (combined chemically or physically,
with the solvent) and dispersed, even at high
concentrations.
More viscid
16. Types of colloids:
Examples of lyophilic sols include sols of gum, gelatin, starch, proteins and
certain polymers (rubber) in organic solvents.
the dispersed phase does not precipitate easily
the sols are quite stable as the solute particle surrounded by two stability
factors: a- negative or positive charge
b- layer of solvent
If the dispersion medium is separated from the dispersed phase, the sol can
be reconstituted by simply remixing with the dispersion medium. Hence,
these sols are called reversible sols.
Prepared simply by dissolving the material in the solvent being used e.g.
dissolution of acacia in water.
17. Types of colloids:
B-lyophobic (solvent repelling) (solvent hating) - The particles
resist solvation and dispersion in the solvent.
- The concentration of particles is usually relatively low.
- Less viscid
- These colloids are easily precipitated on the addition of small
amounts of electrolytes, by heating or by shaking
- Less stable as the particles surrounded only with a layer of positive
or negative charge
- Once precipitated, it is not easy to reconstitute the sol by simple
mixing with the dispersion medium. Hence, these sols are called
irreversible sols.
- Examples of lyophobic sols include sols of metals and their insoluble
compounds like sulphides and oxides.
e.g. gold in water
charge
18. Types of colloids:
Prepared by:
I. Physical method (Bridge‘s arc method)
- This method is employed for obtaining colloidal solutions of metals
e.g. silver, gold, platinum
ice
Dispersion medium
(Water + kOH)
19. I. Physical method (Bridge‘s arc method)
An electric current is struck between two metallic
electrodes placed in a container of water.
The intense heat of the arc converts the metal into
vapours which condensed immediately in the cold water
bath.
This results in the formation of particles of colloidal size.
20. Types of colloids:
II. Chemical method :by oxidation
- Sulphur solution is obtained by bubbling H2S gas through
the solution of an oxidizing agent like HNO3 or Br2 in
water , according to the following equations:
- Br2 + H2S S + 2 HBr
- HNO3 + H2S H2O + NO2 + S
21. Types of colloids:
C- Association / amphiphilic colloids
- Certain molecules termed amphiphiles or surface active
agents, characterized by two regions of opposing
solution affinities within the same molecule.
22. Types of colloids:
- At low concentration: amphiphiles exist separately
(subcolloidal size)
- At high concentration: form aggregates or micelles (50 or
more monomers) (colloidal size)
24. Types of colloids:
Critical micelle concentration (C.M.C) : the concentration
at which micelle form
- The phenomenon of micelle formation can be
explained:
1- below C.M.C: amphiphiles are adsorbed at the air/water
interface
2- As amphiphile concentration is raised: both the
interphase and bulk phase become saturated with
monomers (C.M.C)
3- any further amphiphile added in excess: amphiphiles
aggregate to form micelles
25. Types of colloids:
- In water: the hydrocarbon chains face inwards into the
micelle forming hydrocarbon core and surrounded by
the polar portions of the amphiphile associated with
water molecules.
- In non-polar liquid: the polar heads facing inward and
the hydrocarbon chains are associated with non-polar
liquid.
- At concentrations close to C.M.C spherical
micelles
- At higher concentrations lamellar micelles
28. Types of colloids:
The formation of association colloids is spontaneous,
provided the concentration of amphiphile in solution
exceed C.M.C.
29. Comparison of colloidal sols
Lyophilic Associated Lyophobic
Dispersed phase
(large organic mole.
With colloidal size)
Dispersed phase
(micelles of organic
molec. Or ion –size
below the colloidal
range)
Dispersed phase
(Inorganic particles as
gold)
Molec. of dispersed
phase are solvated
Formed
spontaneously
Hydrophilic and lyophilic
portion are solvated ,
Formed at conc. above
CMC
Not formed
spontaneously
The viscosity ↑ with ↑
the dispersed phase
conc.
The viscosity ↑ with ↑
the micelles conc.
Not greatly increase
Stable dispersion in
presence of
electrolytes
CMC↓ with electrolytes Unstable dispersion in
presence of
electrolytes
30. Optical Properties of Colloids
1-Faraday-Tyndall effect
– when a strong beam of light is
passed through a colloidal
sol, the path of light is
illuminated (a visible cone
formed).
- This phenomenon resulting
from the scattering of light by
the colloidal particles.
31. Optical Properties of Colloids
The same effect is noticed when a beam of sunlight
enters a dark room through a slit when the beam of
light becomes visible through the room.
This happens due to the scattering of light by particles
of dust in the air.
32.
33. Optical Properties of Colloids
2- Electron microscope
- Ultra-microscope has declined in recent years as it
does not able to resolve lyophilic colloids.
- so electron microscope is capable of yielding pictures
of actual particles size, shape and structure of colloidal
particles.
- Electron microscope has high resolving power, as its
radiation source is a beam of high energy electrons,
while that of optical microscope is visible light.
35. Optical Properties of Colloids
3- Light Scattering
- depend on tyndall effect.
- used to give information about particle size and shape and for
determination of molecular weight of colloids.
- Used to study proteins, association colloids and lyophobic sols.
- Scattering described in terms of turbidity, T
- Turbidity: the fractional decrease in intensity due to scattering as
the incident light passes through 1 cm of solution.
- Turbidity is proportional to the molecular weight of lyophilic colloid
36. Optical Properties of Colloids
Hc / T = 1/M + 2Bc
T: turbidity
C: conc of solute in gm / cc of solution
M: molecular weight
B: interaction constant
H: constant for a particular system
37. Kinetic Properties of Colloids
1-Brownian motion
- The zig-zag movement of colloidal
particles continuously and randomly.
This brownian motion arises due to the
uneven distribution of the collisions
between colloid particle and the solvent
molecules.
- Brownian movement was more rapid for
smaller particles.
- It decrease with increase the viscosity of
the medium.
38. Kinetic Properties of Colloids
2- Diffusion
- Particles diffuse spontaneously from a region of higher
conc. To one of lower conc. Until the conc. of the
system is uniform throughout.
- Diffusion is a direct result of Brownian motion.
- Fick's first law used to describe the diffusion:
(The amount of Dq of substance diffusing in time dt
across a plane of area A is directly proportional to the
change of concentration dc with distance traveled
dq = -DA (dc / dx) dt
39. Kinetic Properties of Colloids
D diffusion coefficient
the amount of the material diffused per unit time across
a unit area when dc/dx (conc. gradient) is unity.
- The measured diffusion coeffecient can be used to
determine the radius of particles or molecular weight.
40. Kinetic Properties of Colloids
3- Osmotic pressure
- van 't hoff equation:
π = cRT
- Can be used to determine the molecular weight of
colloid in dilute solution.
- Replacing c by C / M (where C = the grams of solute /
liter of solution, M = molecular weight)
π/C = RT/M
41. Kinetic Properties of Colloids
π = osmotic pressure
R= molar gas constant
4- Sedimentation
- The velocity of sedimentation is given by Stokes‘ Law:
v = d2 (ρi-ρe)g/18η
V = rate of sedimentation
D = diameter of particles
ρ = density of internal phase and external phase
g = gravitational constant
η = viscosity of medium
42. Kinetic Properties of Colloids
5- Viscosity:
- It is the resistance to flow of system under an applied stress. The
more viscous a liquid, the greater the applied force required to
make it flow at a particular rate.
- The viscosity of colloidal dispersion is affected by the shape of
particles of the disperse phase:
Spherocolloids dispersions of low viscosity
Linear particles more viscous dispersions
43. Electric Properties Of Colloids
The particles of a colloidal solution are electrically charged and carry
the same type of charge, either negative or positive.
The colloidal particles therefore repel each other and do not cluster
together to settle down.
The charge on colloidal particles arises because of the dissociation
of the molecular electrolyte on the surface.
E.g. As2S3 has a negative charge
During preparation of colloidal As2S3 , H2S is absorbed on
the surface and dissociate to H+
(lost to the medium) and
S-2
remain on the surface of colloid
.
44. Electric Properties Of
Colloids
Fe(OH)3 is positively charged
Due to self dissociation and loss of OH-
to the medium,so
they become [Fe(OH)3] Fe+3
45. Electrophoresis
Electrophoresis is the most known electrokinetic
phenomena. It refers to the motion of charged particles
related to the fluid under the influence of an applied
electric field.
If an electric potential is applied to a colloid, the charged
colloidal particles move toward the oppositely charged
electrode.
46. Electro-osmosis
It is the opposite in principal to that of electrophoresis.
When electrodes are placed across a clay mass and a
direct current is applied, water in the clay pore space is
transported to the cathodically charged electrode by
electro-osmosis.
Electro-osmotic transport of water through a clay is a
result of diffuse double layer cations in the clay pores
being attracted to a negatively charged electrode or
cathode. As these cations move toward the cathode,
they bring with them water molecules that clump around
the cations as a consequence of their dipolar nature.
48. Sedimentation Potential
The sedimentation potential also called the
(Donnan effect).
It is the potential induced by the fall of a charged
particle under an external force field.
It is analogous to electrophoresis in the sense that a
local electric field is induced as a result of its motion.
if a colloidal suspension has a gradient of concentration
(such as is produced in sedimentation or centrifugation),
then a macroscopic electric field is generated by the
charge imbalance appearing at the top and bottom of
the sample column.
50. Streaming Potential
Differs from electro-osmosis in that the potential is
created by forcing a liquid to flow through a bed or
plug of particles.
52. Stability of colloids
Stabilization serves to prevent colloids from
aggregation.
The presence and magnitude, or absence of a charge
on a colloidal particle is an important factor in the
stability of colloids.
Two main mechanisms for colloid stabilization:
1-Steric stabilization i.e. surrounding each particle with a
protective solvent sheath which prevent adherence due
to Brownian movement
2-electrostatic stabilization i.e. providing the particles with
electric charge
53. Stability of colloids
A- Lyophobic sols:
- Unstable.
- The particles stabilized only by the presence of electrical charges on
their surfaces through the addition of small amount of electrolytes.
- The like charges produce repulsion which prevent coagulation of the
particles and subsequent settling.
- Addition of electrolytes beyond necessary for maximum stability
results in accumulation of opposite ions and decrease zeta
potential coagulation precipitation of colloids.
55. Stability of colloids
- Coagulation also result from mixing of oppositely
charged colloids.
B- Lyophilic sols and association colloids:
- Stable
- Present as true solution
- Addition of moderate amounts of electrolytes not cause
coagulation (opposite lyophobic)
** Salting out:
Definition: agglomeration and precipitation of lyophilic
colloids.
56. Stability of colloids
This is obtained by:
1- Addition of large amounts of electrolytes
- Anions arranged in a decreasing order of precipitating
power: citrate > tartrate > sulfate > acetate > chloride>
nitrate > bromide > iodide
- The precipitation power is directly related to the hydration
of the ion and its ability to separate water molecules from
colloidal particles
2- addition of less polar solvent
- e.g. alcohol, acetone
57. Stability of colloids
- The addition of less polar solvent renders the solvent
mixture unfavourable for the colloids solubility
** Coacervation:
Definition: the process of mixing negatively and positively
charged hydrophilic colloids, and hence the particles
separate from the dispersion to form a layer rich in the
colloidal aggregates (coacervate)
58. Sensitization and protective
colloidal action:
Sensitization: the addition of small amount of
hydrophilic or hydrophobic colloid to a hydrophobic
colloid of opposite charge tend to sensitize
(coagulate) the particles.
Polymer flocculants can bridge individual colloidal
particles by attractive electrostatic interactions.
For example, negatively-charged colloidal silica
particles can be flocculated by the addition of a
positively-charged polymer.
59. Sensitization and protective
colloidal action:
Protection: the addition of large amount of hydrophilic
colloid (protective colloid) to a hydrophobic colloid tend
to stabilize the system.
This may be due to:
The hydrophile is adsorbed as a monomolecular layer on
the hydrophobic particles.