Podcast
Questions and Answers
What is the relationship between specific viscosity and volume fraction in colloids?
What is the relationship between specific viscosity and volume fraction in colloids?
- Specific viscosity is proportional to the square of the volume fraction.
- Specific viscosity is inversely proportional to the volume fraction.
- Specific viscosity is equal to 2.5 times the volume fraction. (correct)
- Specific viscosity is constant regardless of volume fraction.
Which statement accurately describes the effect of particle shape on the viscosity of colloidal solutions?
Which statement accurately describes the effect of particle shape on the viscosity of colloidal solutions?
- Spherical colloid particles lead to a higher viscosity than linear particles. (correct)
- Shape affects viscosity only in non-colloidal dispersions.
- Viscosity is independent of the shape of the colloidal particles.
- Linear colloid particles exhibit lower viscosity than spherical particles.
What best describes the stability of lyophilic colloids compared to lyophobic colloids?
What best describes the stability of lyophilic colloids compared to lyophobic colloids?
- Lyophilic colloids are more stable due to strong attraction with the dispersion medium. (correct)
- Both types are equally stable as they both precipitate easily.
- Lyophilic colloids are less stable due to high coagulation rates.
- Lyophilic colloids are unstable but can easily reform after separation.
What role does electrical charge play in the stability of colloidal dispersions?
What role does electrical charge play in the stability of colloidal dispersions?
Which characteristic is NOT associated with lyophilic colloids?
Which characteristic is NOT associated with lyophilic colloids?
How does ionization contribute to the electrical charge of colloidal particles?
How does ionization contribute to the electrical charge of colloidal particles?
What term best describes colloids that have no affinity for the dispersion medium?
What term best describes colloids that have no affinity for the dispersion medium?
Which of the following mechanisms does NOT contribute to the charging of interfaces in colloidal systems?
Which of the following mechanisms does NOT contribute to the charging of interfaces in colloidal systems?
Which of the following would be considered a lyophobic colloid?
Which of the following would be considered a lyophobic colloid?
Which statement is true regarding lyophobic colloids?
Which statement is true regarding lyophobic colloids?
What is a key characteristic of the dispersed phase in lyophilic colloids?
What is a key characteristic of the dispersed phase in lyophilic colloids?
How do lyophilic colloids compare to lyophobic colloids in biological systems?
How do lyophilic colloids compare to lyophobic colloids in biological systems?
Which mechanism leads to the formation of lyophilic colloids?
Which mechanism leads to the formation of lyophilic colloids?
What does osmotic pressure primarily influence in a colloidal solution?
What does osmotic pressure primarily influence in a colloidal solution?
Which equation is used for determining the molecular weight of colloids in dilute solution?
Which equation is used for determining the molecular weight of colloids in dilute solution?
How does the shape of linear colloidal particles affect viscosity in a dispersion?
How does the shape of linear colloidal particles affect viscosity in a dispersion?
What is the primary purpose of measuring viscosity in colloidal dispersions?
What is the primary purpose of measuring viscosity in colloidal dispersions?
In the Van't Hoff equation, what does the variable 'R' represent?
In the Van't Hoff equation, what does the variable 'R' represent?
What effect does a solute have on osmotic pressure in a solution?
What effect does a solute have on osmotic pressure in a solution?
Which of the following statements about crystalloid solutions is accurate?
Which of the following statements about crystalloid solutions is accurate?
What does the variable 'φ' represent in Einstein's equation for viscosity?
What does the variable 'φ' represent in Einstein's equation for viscosity?
What is the primary purpose of adding a stabilizer during the preparation of lyophobic colloids?
What is the primary purpose of adding a stabilizer during the preparation of lyophobic colloids?
Which mechanical dispersion method involves the use of a rotating vessel with metal balls?
Which mechanical dispersion method involves the use of a rotating vessel with metal balls?
What is the term for converting freshly prepared precipitate into colloidal form using an electrolyte?
What is the term for converting freshly prepared precipitate into colloidal form using an electrolyte?
In a colloid mill setup, which configuration allows for the disintegration of solid particles?
In a colloid mill setup, which configuration allows for the disintegration of solid particles?
Which method employs high-speed rotation to achieve particle dispersion?
Which method employs high-speed rotation to achieve particle dispersion?
What causes peptization to occur when an electrolyte is added to a precipitate?
What causes peptization to occur when an electrolyte is added to a precipitate?
What happens to the stability of lyophobic colloids when suitable stabilizers are not added?
What happens to the stability of lyophobic colloids when suitable stabilizers are not added?
What role do ultrasonic waves play in the preparation of lyophobic colloids?
What role do ultrasonic waves play in the preparation of lyophobic colloids?
What type of colloidal solution can be obtained by excessive cooling in an organic solvent?
What type of colloidal solution can be obtained by excessive cooling in an organic solvent?
Which process involves passing hot vapor through water to condense vapor into a precipitate?
Which process involves passing hot vapor through water to condense vapor into a precipitate?
What distinguishes lyophilic colloids from lyophobic colloids?
What distinguishes lyophilic colloids from lyophobic colloids?
What is a common property of lyophobic colloids?
What is a common property of lyophobic colloids?
When a true solution is mixed with an excess of another solvent, what type of solution is typically formed?
When a true solution is mixed with an excess of another solvent, what type of solution is typically formed?
What will happen when a concentrated solution is poured into a liquid in which the solute is insoluble?
What will happen when a concentrated solution is poured into a liquid in which the solute is insoluble?
In the comparison of colloids, what is true about association colloids?
In the comparison of colloids, what is true about association colloids?
What is a characteristic of lyophobic colloids when electrolytes are added?
What is a characteristic of lyophobic colloids when electrolytes are added?
What is the primary effect of increasing the valency of an effective ion in a colloidal system?
What is the primary effect of increasing the valency of an effective ion in a colloidal system?
Which process describes the separation of a colloid-rich layer from a lyophilic sol?
Which process describes the separation of a colloid-rich layer from a lyophilic sol?
What occurs during complex coacervation?
What occurs during complex coacervation?
What is the role of hydrophilic colloids in sensitization?
What is the role of hydrophilic colloids in sensitization?
What is one method of microencapsulation derived from coacervation?
What is one method of microencapsulation derived from coacervation?
How do hydrophilic colloids affect the stability of hydrophobic colloids in the presence of electrolytes?
How do hydrophilic colloids affect the stability of hydrophobic colloids in the presence of electrolytes?
What is the result of boiling a sol such as silver halides dispersed in water?
What is the result of boiling a sol such as silver halides dispersed in water?
Which type of ions are involved in the reaction that leads to coacervation?
Which type of ions are involved in the reaction that leads to coacervation?
Which method is used to measure the turbidity of a solution?
Which method is used to measure the turbidity of a solution?
What is the primary characteristic of Brownian motion observed in colloidal particles?
What is the primary characteristic of Brownian motion observed in colloidal particles?
What happens to Brownian motion as the viscosity of the dispersion medium increases?
What happens to Brownian motion as the viscosity of the dispersion medium increases?
How is turbidity mathematically expressed in relation to molecular weight?
How is turbidity mathematically expressed in relation to molecular weight?
What effect does the size of a colloidal particle have on Brownian motion?
What effect does the size of a colloidal particle have on Brownian motion?
Which particle shapes have been identified in colloids?
Which particle shapes have been identified in colloids?
Which equipment is suitable for measuring turbidity in a colloidal solution?
Which equipment is suitable for measuring turbidity in a colloidal solution?
What does the term 'turbidity' refer to in a colloidal system?
What does the term 'turbidity' refer to in a colloidal system?
What primarily influences the erythrocyte sedimentation rate (ESR)?
What primarily influences the erythrocyte sedimentation rate (ESR)?
Under which conditions is the erythrocyte sedimentation rate generally elevated?
Under which conditions is the erythrocyte sedimentation rate generally elevated?
Which factor does NOT contribute to the sedimentation of red blood cells?
Which factor does NOT contribute to the sedimentation of red blood cells?
What charge do silver iodide particles acquire when there is an excess of silver ions in the reaction mixture?
What charge do silver iodide particles acquire when there is an excess of silver ions in the reaction mixture?
How does osmotic pressure relate to molecular weight according to Van't Hoff's law?
How does osmotic pressure relate to molecular weight according to Van't Hoff's law?
What defines the combination of a positively charged surface and surrounding counter ions in colloids?
What defines the combination of a positively charged surface and surrounding counter ions in colloids?
What is the main characteristic of the internal solution in osmosis?
What is the main characteristic of the internal solution in osmosis?
What does the Tyndall effect demonstrate in colloidal solutions?
What does the Tyndall effect demonstrate in colloidal solutions?
Which ions are considered potential determining ions for metal oxides and hydroxides?
Which ions are considered potential determining ions for metal oxides and hydroxides?
What happens to red blood cells during inflammation that influences their sedimentation rate?
What happens to red blood cells during inflammation that influences their sedimentation rate?
Which statement is true regarding the application of centrifugal force in studying micellar properties?
Which statement is true regarding the application of centrifugal force in studying micellar properties?
What is the primary function of the Ultramicroscope?
What is the primary function of the Ultramicroscope?
What results from the selective adsorption of ions around a colloidal particle?
What results from the selective adsorption of ions around a colloidal particle?
Which factor influences the color of a hydrophobic sol?
Which factor influences the color of a hydrophobic sol?
What is the difference in potential between the compact layer and the bulk of the solution known as?
What is the difference in potential between the compact layer and the bulk of the solution known as?
Why is there a practical lower limit of about 1 micron in sedimentation studies under gravity?
Why is there a practical lower limit of about 1 micron in sedimentation studies under gravity?
When excess iodide ions are present during the reaction of silver iodide formation, what charge do the AgI particles acquire?
When excess iodide ions are present during the reaction of silver iodide formation, what charge do the AgI particles acquire?
Which of the following statements about the particle size of colloids is accurate?
Which of the following statements about the particle size of colloids is accurate?
How do larger colloidal particles interact with light compared to smaller particles?
How do larger colloidal particles interact with light compared to smaller particles?
What type of layer consists of the fixed charges on the particle surface and counter ions in the surrounding medium?
What type of layer consists of the fixed charges on the particle surface and counter ions in the surrounding medium?
What is a distinguishing feature of true solutions in relation to light scattering?
What is a distinguishing feature of true solutions in relation to light scattering?
What is the effect of increasing the concentration of either type of potential determining ion in the double layer?
What is the effect of increasing the concentration of either type of potential determining ion in the double layer?
What does the term 'Tyndall cone' refer to in colloidal chemistry?
What does the term 'Tyndall cone' refer to in colloidal chemistry?
Which instrument is used to observe individual sol particles at high magnification?
Which instrument is used to observe individual sol particles at high magnification?
What is the main purpose of protective colloids in relation to hydrophobic colloids?
What is the main purpose of protective colloids in relation to hydrophobic colloids?
Which of the following is a disadvantage of colloidal preparations?
Which of the following is a disadvantage of colloidal preparations?
What is a significant advantage of colloidal preparations in pharmaceuticals?
What is a significant advantage of colloidal preparations in pharmaceuticals?
What is one reason for the use of colloidal gold in medicine?
What is one reason for the use of colloidal gold in medicine?
What challenge is associated with the preparation of lyophobic colloids?
What challenge is associated with the preparation of lyophobic colloids?
How do colloids contribute to the dispersion of insoluble materials?
How do colloids contribute to the dispersion of insoluble materials?
What drawback is associated with ionic silver salt in biological systems?
What drawback is associated with ionic silver salt in biological systems?
What are colloidal preparations commonly used for in the paint industry?
What are colloidal preparations commonly used for in the paint industry?
What characteristic primarily distinguishes lyophilic colloids from lyophobic colloids?
What characteristic primarily distinguishes lyophilic colloids from lyophobic colloids?
Which of the following statements accurately describes the stability of lyophobic colloids?
Which of the following statements accurately describes the stability of lyophobic colloids?
What process is reflected in the spontaneous formation of lyophilic colloids when combined with a dispersion medium?
What process is reflected in the spontaneous formation of lyophilic colloids when combined with a dispersion medium?
What type of colloidal particles are characterized by having no affinity for the dispersion medium?
What type of colloidal particles are characterized by having no affinity for the dispersion medium?
Which example accurately represents a hydrophobic colloid?
Which example accurately represents a hydrophobic colloid?
What is the nature of the stability factors surrounding a solute particle in lyophilic colloids?
What is the nature of the stability factors surrounding a solute particle in lyophilic colloids?
Which statement best characterizes lyophilic colloids in biological systems?
Which statement best characterizes lyophilic colloids in biological systems?
What happens when the dispersion medium is removed from lyophilic colloids?
What happens when the dispersion medium is removed from lyophilic colloids?
Which of the following best describes the nature of association colloids?
Which of the following best describes the nature of association colloids?
What is the defining property of macromolecular colloids?
What is the defining property of macromolecular colloids?
In sol systems where water is the dispersion medium, what term is used to describe the system?
In sol systems where water is the dispersion medium, what term is used to describe the system?
How does the rigidity of a gel arise?
How does the rigidity of a gel arise?
Which of the following is characteristic of lyophobic colloids?
Which of the following is characteristic of lyophobic colloids?
What is the primary interaction that holds multimolecular colloids together?
What is the primary interaction that holds multimolecular colloids together?
What type of dispersion medium is used in the formation of foams?
What type of dispersion medium is used in the formation of foams?
Which example best represents an aerosol in colloidal systems?
Which example best represents an aerosol in colloidal systems?
What best describes lyophobic colloids?
What best describes lyophobic colloids?
Which statement accurately differentiates lyophilic colloids from lyophobic colloids?
Which statement accurately differentiates lyophilic colloids from lyophobic colloids?
What characteristic of lyophilic colloids allows them to be unstable in certain conditions?
What characteristic of lyophilic colloids allows them to be unstable in certain conditions?
Which of the following substances is an example of a lyophilic colloid?
Which of the following substances is an example of a lyophilic colloid?
What is a fundamental property of lyophobic colloids that distinguishes them from lyophilic colloids?
What is a fundamental property of lyophobic colloids that distinguishes them from lyophilic colloids?
How do lyophilic colloids behave when the dispersion medium is removed?
How do lyophilic colloids behave when the dispersion medium is removed?
Why are lyophobic colloids referred to as extrinsic colloids?
Why are lyophobic colloids referred to as extrinsic colloids?
What mechanism leads to the stability of lyophilic colloids in a dispersion medium?
What mechanism leads to the stability of lyophilic colloids in a dispersion medium?
What primarily determines the osmotic pressure in a colloidal solution?
What primarily determines the osmotic pressure in a colloidal solution?
What characteristic of linear colloidal dispersions affects their viscosity?
What characteristic of linear colloidal dispersions affects their viscosity?
Which equation is specifically used to relate osmotic pressure to the molecular weight of colloids?
Which equation is specifically used to relate osmotic pressure to the molecular weight of colloids?
How does the viscosity of a colloidal dispersion change with respect to its volume fraction?
How does the viscosity of a colloidal dispersion change with respect to its volume fraction?
What key property does osmotic pressure NOT influence in a colloidal system?
What key property does osmotic pressure NOT influence in a colloidal system?
In the context of viscosities, what does the variable $η_o$ represent in Einstein's equation?
In the context of viscosities, what does the variable $η_o$ represent in Einstein's equation?
What is the primary function of viscosity measurements in colloidal dispersions?
What is the primary function of viscosity measurements in colloidal dispersions?
Which component in the Van't Hoff equation does not contribute directly to osmotic pressure?
Which component in the Van't Hoff equation does not contribute directly to osmotic pressure?
What happens to the surface charge of silver iodide particles when there is an excess of Ag+ ions during the reaction?
What happens to the surface charge of silver iodide particles when there is an excess of Ag+ ions during the reaction?
Which ions are termed potential determining ions for magnesium hydroxide?
Which ions are termed potential determining ions for magnesium hydroxide?
What characterizes the electric double layer surrounding colloidal particles?
What characterizes the electric double layer surrounding colloidal particles?
What is the primary effect observed due to the distribution of charge in a colloidal particle's electric double layer?
What is the primary effect observed due to the distribution of charge in a colloidal particle's electric double layer?
How does an increase in hydroxide concentration affect aluminum hydroxide particles?
How does an increase in hydroxide concentration affect aluminum hydroxide particles?
What defines the Stern double layer in colloidal systems?
What defines the Stern double layer in colloidal systems?
In a colloidal reaction involving excess NaI, what is the resulting charge on the silver iodide particles?
In a colloidal reaction involving excess NaI, what is the resulting charge on the silver iodide particles?
Which term best describes the charged atmosphere formed around colloidal particles due to selective adsorption?
Which term best describes the charged atmosphere formed around colloidal particles due to selective adsorption?
What happens to the adsorbed electrolyte on sol particles when boiling occurs?
What happens to the adsorbed electrolyte on sol particles when boiling occurs?
Which of the following best describes the process of complex coacervation?
Which of the following best describes the process of complex coacervation?
How does the addition of a hydrophilic colloid affect a hydrophobic colloid?
How does the addition of a hydrophilic colloid affect a hydrophobic colloid?
What role do polymer flocculants play in a colloidal system?
What role do polymer flocculants play in a colloidal system?
What is one of the main advantages of microencapsulation for drugs?
What is one of the main advantages of microencapsulation for drugs?
Which of the following statements correctly describes sensitization?
Which of the following statements correctly describes sensitization?
What is the primary factor that determines the coagulation power of an effective ion?
What is the primary factor that determines the coagulation power of an effective ion?
What phenomenon is responsible for the blue appearance of the sky?
What phenomenon is responsible for the blue appearance of the sky?
What does coacervation lead to when two lyophilic colloids are mixed?
What does coacervation lead to when two lyophilic colloids are mixed?
Which of the following is NOT a common application of colloids?
Which of the following is NOT a common application of colloids?
How do soap solutions function to remove dirt?
How do soap solutions function to remove dirt?
Which colloidal dispersion is used as a plasma substitute?
Which colloidal dispersion is used as a plasma substitute?
What effect do ions produced by acid have on colloidal particles in milk?
What effect do ions produced by acid have on colloidal particles in milk?
What is a characteristic use of colloidal silver in medicine?
What is a characteristic use of colloidal silver in medicine?
Which of the following materials is colloidal in nature?
Which of the following materials is colloidal in nature?
Which statement best describes the role of colloidal macromolecules in pharmaceuticals?
Which statement best describes the role of colloidal macromolecules in pharmaceuticals?
Flashcards
Lyophilic Colloids
Lyophilic Colloids
Colloids where the dispersed material strongly attracts the solvent.
Lyophobic Colloids
Lyophobic Colloids
Colloids where the dispersed material has little attraction for the solvent.
Dispersion Medium
Dispersion Medium
The substance in which another substance is dispersed to form a colloid.
Dispersed Phase
Dispersed Phase
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Stability Factors (Lyophilic)
Stability Factors (Lyophilic)
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Reversible Sols
Reversible Sols
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Hydrophobic Colloids
Hydrophobic Colloids
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Extrinsic Colloids
Extrinsic Colloids
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Lyophobic colloids
Lyophobic colloids
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Dispersion methods
Dispersion methods
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Condensation methods
Condensation methods
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Mechanical disintegration
Mechanical disintegration
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Ball mill
Ball mill
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Colloid mill
Colloid mill
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Peptization
Peptization
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Peptizing agent
Peptizing agent
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Thermal Condensation
Thermal Condensation
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Excessive Cooling
Excessive Cooling
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Solvent Exchange
Solvent Exchange
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Reducing Solubility
Reducing Solubility
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Lyophilic Colloid Preparation
Lyophilic Colloid Preparation
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Lyophobic Colloid Charge
Lyophobic Colloid Charge
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Association Colloids
Association Colloids
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Lyophilic Colloid Viscosity
Lyophilic Colloid Viscosity
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Semimembrane
Semimembrane
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Crystalloid Solutions
Crystalloid Solutions
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Osmotic Pressure
Osmotic Pressure
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Oncotic Pressure
Oncotic Pressure
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Van't Hoff Equation
Van't Hoff Equation
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Viscosity
Viscosity
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Einstein's Viscosity Equation
Einstein's Viscosity Equation
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Viscosity and Molecular Weight
Viscosity and Molecular Weight
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Relative Viscosity
Relative Viscosity
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Specific Viscosity
Specific Viscosity
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Colloidal Stability
Colloidal Stability
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Surface Charging Mechanisms
Surface Charging Mechanisms
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Ionization & Surface Charge
Ionization & Surface Charge
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Coagulation of Sols
Coagulation of Sols
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Coacervation
Coacervation
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Complex Coacervation
Complex Coacervation
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Microencapsulation
Microencapsulation
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Sensitization
Sensitization
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Protective Colloidal Action
Protective Colloidal Action
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Precipitating Power
Precipitating Power
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Valency
Valency
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Lyophilic Colloid
Lyophilic Colloid
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Lyophobic Colloid
Lyophobic Colloid
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Dispersion Medium
Dispersion Medium
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Dispersed Phase
Dispersed Phase
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Lyophilic Colloid Stability
Lyophilic Colloid Stability
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Reversible Sol
Reversible Sol
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Hydrophobic Colloid
Hydrophobic Colloid
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Lyophilic Colloid Preparation
Lyophilic Colloid Preparation
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Tyndall Effect
Tyndall Effect
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Ultramicroscope
Ultramicroscope
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Particle size (colloids)
Particle size (colloids)
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Color of hydrophobic sol
Color of hydrophobic sol
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Electron Microscope
Electron Microscope
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Particle Size Estimation
Particle Size Estimation
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Particle Shape Estimation
Particle Shape Estimation
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Particle Interactions Estimation
Particle Interactions Estimation
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Brownian Motion
Brownian Motion
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Turbidity
Turbidity
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Ultramicroscope
Ultramicroscope
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Colloidal Particles
Colloidal Particles
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Particle Size Estimation
Particle Size Estimation
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Turbidity Equation
Turbidity Equation
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Kinetic Properties
Kinetic Properties
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Brownian Motion effect
Brownian Motion effect
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Sedimentation Rate
Sedimentation Rate
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Westergren tube
Westergren tube
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Osmotic Pressure
Osmotic Pressure
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Van't Hoff's Law
Van't Hoff's Law
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Erythrocyte Sedimentation Rate (ESR)
Erythrocyte Sedimentation Rate (ESR)
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Micellar Properties
Micellar Properties
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Balance Method
Balance Method
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Centrifugal Force
Centrifugal Force
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Electrical Double Layer
Electrical Double Layer
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Potential Determining Ions
Potential Determining Ions
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Zeta Potential
Zeta Potential
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Electrokinetic Potential
Electrokinetic Potential
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AgI Colloid Charge
AgI Colloid Charge
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Electric Double Layer
Electric Double Layer
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Stern Double Layer
Stern Double Layer
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Coagulation of Sols
Coagulation of Sols
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Protective Colloidal Action
Protective Colloidal Action
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Hydrophilic Colloid
Hydrophilic Colloid
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Hydrophobic Colloid
Hydrophobic Colloid
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Colloidal Stability
Colloidal Stability
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Tyndall Effect
Tyndall Effect
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Advantages of Colloids in Medicine
Advantages of Colloids in Medicine
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Disadvantages of Colloids
Disadvantages of Colloids
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Protective Colloid
Protective Colloid
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Solid-sol
Solid-sol
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Sol
Sol
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Aerosol (solid)
Aerosol (solid)
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Gel
Gel
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Emulsion
Emulsion
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Liquid Aerosol
Liquid Aerosol
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Multimolecular Colloid
Multimolecular Colloid
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Macromolecular Colloid
Macromolecular Colloid
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Lyophilic Colloids
Lyophilic Colloids
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Lyophobic Colloids
Lyophobic Colloids
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Dispersion Medium
Dispersion Medium
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Dispersed Phase
Dispersed Phase
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Lyophilic Colloid Stability
Lyophilic Colloid Stability
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Reversible Sol
Reversible Sol
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Hydrophobic Colloid
Hydrophobic Colloid
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Lyophilic Colloid Preparation
Lyophilic Colloid Preparation
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Semipermeable Membrane
Semipermeable Membrane
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Crystalloid Solutions
Crystalloid Solutions
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Osmotic Pressure
Osmotic Pressure
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Oncotic Pressure
Oncotic Pressure
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Van't Hoff Equation
Van't Hoff Equation
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Viscosity
Viscosity
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Einstein's Viscosity Equation
Einstein's Viscosity Equation
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Viscosity and Molecular Weight
Viscosity and Molecular Weight
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Electrical Double Layer
Electrical Double Layer
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Potential Determining Ions
Potential Determining Ions
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Zeta Potential
Zeta Potential
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AgI Colloid Charge
AgI Colloid Charge
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Stern Double Layer
Stern Double Layer
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Coagulation of Sols
Coagulation of Sols
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Protective Colloidal Action
Protective Colloidal Action
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Hydrophilic Colloid
Hydrophilic Colloid
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Precipitating Power
Precipitating Power
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Coagulation of Sols
Coagulation of Sols
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Coacervation
Coacervation
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Complex Coacervation
Complex Coacervation
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Microencapsulation
Microencapsulation
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Sensitization (colloids)
Sensitization (colloids)
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Protective Colloidal Action
Protective Colloidal Action
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Valency
Valency
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Tyndall effect
Tyndall effect
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Colloidal silver
Colloidal silver
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Colloidal stability
Colloidal stability
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Coagulation of sols
Coagulation of sols
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Protective colloids
Protective colloids
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Application of colloids (industrial)
Application of colloids (industrial)
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Colloidal Dispersion
Colloidal Dispersion
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Applications in medicine
Applications in medicine
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Study Notes
Dispersions
- Dispersed systems consist of two phases: particulate matter (dispersed phase) and continuous phase (dispersion medium/solvent).
- Based on the size of the dispersed phase, three types of dispersed systems are generally considered: molecular dispersions, colloidal dispersions, and coarse dispersions.
Introduction to Colloidal Dispersions
- The word colloid comes from the Greek words 'kolla' (glue) and 'eidos' (like), thus colloidal particles are glue-like substances.
- Colloidal systems consist of two phases: a dispersed phase (discontinuous phase) and a dispersion medium (continuous phase).
- A colloid is defined as a heterogeneous (two-phase) system consisting of minute particles (1 nm to 1000 nm) microscopically dispersed into a continuous phase.
- Examples of natural colloids include fogs, mists, smoke, and ferric hydrosol.
Examples of Colloidal Systems
- Foams
- Milk
- Fog/smoke
- Detergents
- Aerogel
- Blood
- Paints
- Cosmetics
Classification of Dispersed Systems
- Molecular dispersion: Particle size less than 1 nm. Invisible in electron microscopes; pass through ultrafilters and semipermeable membranes; undergo rapid diffusion. Examples include oxygen molecules and ordinary ions.
- Colloidal dispersion: Particle size from 1 nm to 0.5 µm. Invisible in ordinary microscopes but visible in electron microscopes; pass through filter paper but do not pass semipermeable membranes; diffuse very slowly. Examples include colloidal silver sols and natural/synthetic polymers.
- Coarse dispersion: Particle size greater than 0.5 µm. Visible under a microscope; do not pass through normal filter paper; do not dialyze through semipermeable membranes; do not diffuse. Examples include grains of sand, emulsions, and red blood cells.
Properties of Solutions, Colloids, and Suspensions
| Property | Solution | Colloid | Suspension |
|---|---|---|---|
| Particle Size | 0.1-1.0 nm | 1-1000 nm | >1000 nm |
| Settles on Standing? | No | No | Yes |
| Filter with Paper? | No | No | Yes |
| Separate by Dialysis? | Yes | Borderline | No |
| Homogeneous? | Yes | Borderline | No |
Size and Shape of Colloidal Particles
- Colloidal particles may have various shapes and sizes.
- Particle shape and the dispersion medium affect surface area, attractive forces, flow, sedimentation, and osmotic pressure.
- Size affects color. Larger sizes tend to change the color of a suspension (e.g., red gold sol to blue).
Forces in Colloidal Particle Interactions
- Excluded volume repulsion: The space a molecule occupies in a liquid, which is inaccessible to other molecules.
- Van der Waals forces: Attractions or repulsions between molecules (excluding covalent, hydrogen, and electrostatic interactions).
- Electrostatic interaction: Charged colloidal particles exert forces of attraction or repulsion. Factors such as charge of the dispersed phase, dispersion medium and mobility affect colloids.
- Steric forces(Born repulsion): Repulsion due to overlapping electron clouds when molecules are in close proximity. This repulsion affects particle shape, conformation, and reactivity.
Classification of Colloids
- Physical state of dispersed phase and dispersion medium.
- Molecular size of dispersed phase.
- Nature of interaction between dispersed phase and dispersion medium.
- Appearance of colloids.
- Electric charge on dispersion phase.
Physical State of Dispersed Phase and Dispersion Medium
- Solid in solid (solid-sol) - e.g., coloured glass, gemstones
- Solid in liquid (sol) - e.g., ink, blood
- Solid in gas (aerosol) - e.g., smoke
- Liquid in liquid (emulsion) - e.g., milk, cream
- Liquid in gas (liquid aerosol) - e.g., fog
- Gas in solid (solid form) - e.g., pumice stone
- Gas in liquid (foam) - e.g, shaving cream
- Gas in gas - (none) e.g. all gases are miscible.
Molecular Size of the Dispersed Phase
- Multimolecular colloids: Individual particles (atoms or small molecules) aggregate due to weak van der Waals forces (e.g., gold sol, sulphur sol).
- Macromolecular colloids: Particles (e.g., cellulose, starch, proteins) are sufficiently large to exhibit colloidal properties.
Appearance of Colloids (Various types)
-
Sols: Colloidal solution appearing as a fluid (e.g., dispersion of solids in liquids.)
-
Gels: Colloidal system which transforms into solid or semisolids under certain concentration/temperature (“sets”). The rigidity of a gel is due to the intertwining network trapping the dispersion medium. (e.g., jelly, butter, cheese, curd).
Nature of interaction between dispersed phase and dispersion medium
-
Lyophilic colloids (solvent-loving): Have a strong affinity for the dispersion medium; are quite stable when separated; easy to reconstitute. Example include hydrophilic colloids (solvent is water) such as acacia, insulin in water. Types of lyophilic colloids include hydrophilic and lipophilic.
-
Lyophobic colloids (solvent-hating): Have very weak affinity for the dispersion medium; easily coagulate/are not reversible; unstable when separated. Examples include synthetic polymers, metal hydroxides, metal sols (e.g. gold sol).
-
Association colloids (amphiphilic): Have both hydrophilic and hydrophobic parts in the same molecule (e.g., surfactants soap, detergents). Exhibit different properties at different concentrations. Examples include anionic, cationic, non-ionic, and ampholytic colloids.
Lyophilic Colloids
- More stable than lyophobic colloids because of strong attraction between dispersed phase and dispersion medium (e.g. water).
- Stable as solute particle is surrounded by two factors:
- Charge
- Solvent Layer
- Easily reversible in nature (if dispersion medium is separated from the dispersed phase the sol can be reconstituted by simply remixing with the dispersion medium).
Lyophobic Colloids
- Instability, and coagulation if dispersed phase is separated from dispersion media.
- Poorly hydrated.
- Examples: metal hydroxides, metal sols (e.g., gold sols)
Preparation of Lyophobic Colloids
- Dispersion Methods: Breaking larger particles into colloidal dimensions (e.g. ball mill, colloid mill, ultrasonic treatment, Bredig's arc method).
- Condensation Methods: Aggregating smaller particles to form particles of colloidal size (e.g. chemical reactions, change in solvent).
Mechanical Dispersion Methods
- Ball mill: Uses rotating vessel with metal balls to crush/disperse material in a suitable medium.
- Colloid mill: Uses two rotating plates (fixed or opposite direction) to disperse material in a medium.
Peptization and Ultrasonic Waves
- The conversion from a freshly prepared precipitate to colloidal form by the addition of appropriate electrolytes is called peptization.
- Electrolytes work by being adsorbing ions that the particles will disperse.
Bredig's Arc Method
- Dipping metal electrodes into the dispersion medium and striking an electric arc between these electrodes generates intense heat for metal vaporization.
- Condensation of metal results in colloidal sized particles.
Condensation Methods (Association Methods)
- Chemical reactions and change in solvent are used to aggregate sub-colloidal particles.
Oxidation, Reduction, Hydrolysis, and Double Decomposition Reactions
- Oxidation: Addition of oxygen and removal of hydrogen (e.g., preparing colloidal sulfur by oxidizing H₂S).
- Reduction: Addition of hydrogen or removal of oxygen (e.g., preparing gold sol with stannous chloride).
- Hydrolysis: Breakdown of water (e.g., preparing metal hydroxides by boiling their corresponding chlorides).
- Double Decomposition: Reactions where two compounds react to produce two new compounds. (e.g. , preparing arsenous sulfide by passing hydrogen sulfide gas ).
Change of Solvent
- Methods for preparing colloids by altering the solvent.
- Thermal Condensation: Passing of hot vapours through cold water to form precipitates (e.g., mercury and sulphur).
- Excessive Cooling: Freezing a solution of two substances to form colloids of the other substance within the first. Example, freezing a solution of water in CHCl3 or ether.
- Exchange of Solvent : Mixing a solvent soluble in a sol that is insoluble in another substance. Adding a solution of sulfur in alcohol into an excess of water, e.g, results in a milky sulfur colloid.
- Reducing Solubility: Adding a concentrated solution to a different liquid produces a precipitate due to supersaturation.
Colloid Stability Mechanisms
- Steric Stabilization: Surrounding colloidal particles with a protective layer preventing them from aggregating.
- Electrostatic Stabilization: Providing colloidal particles with a charge to create repulsive forces between them .
Properties of Colloids
- Physical Properties: Heterogeneity, visibility of dispersed particles, stability, and filterability. Particle size, and color (scattering of light).
- Optical Properties: Tyndall effect (scattering of light by colloidal particles).
- Mechanical Properties: Brownian motion, diffusion, sedimentation, osmotic pressure, and viscosity.
- Electrical Properties: electrical charge acquired on the surface of colloidal particles (e.g. from ion dissolution, ionization, and ion adsorption).
Instruments of Detection
- Ultramicroscope: Uses Tyndall effect to observe light scattered by colloidal particles.
- Electron Microscope: Uses beams of electrons to visualize colloidal particles with high magnification.
Importance of Light Scattering Measurements
- Estimating particle size
- Estimating particle shape
- Estimating particle interactions
Methods for purifying colloidal solutions
- Dialysis: Separating colloidal particles from smaller solutes by using a semi-permeable membrane.
- Electro dialysis: Increasing dialysis by applying an electrical potential.
- Ultrafiltration: Filtering colloidal solutions by using ultrafilters (with smaller pores) under pressure.
- Ultracentrifugation: High-speed centrifugation to separate colloidal particles from impurities (based on sedimentation).
Mechanical Properties
- Kinetic properties relating to particle motion.
- Brownian Motion: rapid zig-zag motion of colloidal particles due to collisions with the dispersion medium molecules.
- Diffusion: Movement of colloidal particles/solutes from high to low concentration regions.
- Sedimentation: Settling of particles under the influence of gravity.
- Osmotic Pressure: Pressure exerted by solutes in a solution.
- Viscosity: Resistance to flow.
Electrical Charge of Dispersion Phase
- Colloidal particles exhibit surface charge (due to ionization of surface groups or other factors).
- Positive Colloids: Particles carry positive charge (e.g., metal hydroxides).
- Negative Colloids: Particles carry negative charge (e.g., Ag sol, Cu sol).
Electrical Properties of Interfaces (various aspects)
- Ion dissolution.
- Ionization.
- Ion adsorption.
Suit Ionization
- pH at which the colloidal particles has no electrical charge. The particles/protein is least soluble at this point.
Osmotic Pressure
- Method for determining the molecular weight of colloids in dilute solution.
- Based on van't Hoff's law (π = RTC/M). Measures the pressure (π) needed to prevent osmotic flow of water.
Viscosity
- Resistance of a fluid to flow under applied pressure.
- Viscosity of colloids dependent on particle shape and solvation.
- Related to MW, shape and particle size of dispersed phase.
- Equations for viscosity calculated using a viscometer.
Coacervation and Microencapsulation
- Separation of colloids and formation of a dispersion layer.
- Formation of particles (coacervates) rich in colloids.
- The process used to coat or encapsulate materials.
- Coating protects material from degradation.
Sensitization and Protective Colloidal Action
- Addition of a hydrophilic colloid to a hydrophobic colloid to increase stability and reduce protein precipitation.
- The hydrophobic colloid particles form a protective layer to prevent precipitation/aggregation.
- The solution used to protect is called the protective colloid.
Advantages and Disadvantages of Colloidal Preparations
- Advantages: higher catalytic activity, attractive color, better taste/texture, improved solubility/absorption.
- Disadvantages: increased toxicity, difficult preparation/stabilization, stability issues.
Additional Advantages of Colloids
- Dispersion of normally insoluble materials.
- Drug delivery/antibiotics.
- Used in paints, inks, and other products.
- Removal of dirt particles, etc.
Applications of Colloids
- Paints, adhesives, and inks.
- Water/sewage treatment, and oil recovery.
- Research (e.g., high-resolution chromatography).
- Medical (e.g., drug delivery, diagnostics).
- Chemical (e.g., catalysts, rheological studies).
Colloid-Based Delivery Systems for Therapeutics
- Various systems for delivering drugs/treatments, based on different size ranges.
- Microspheres
- Microparticles
- Emulsions
- Liposomes
- Micelles
- Nanoparticles
- Nanocrystals
- Quantum dots
Pharmaceutical Applications of Colloids
- effective germicides
- Drug delivery
- Disease diagnosis (e.g., syphilis)
- Plasma substitutes of proteins (e.g. starch).
- Coating pharmaceutical products.
- Improving solubility and stability.
Coagulation
- The process or term for particles aggregating and settling due to the removal of repulsive forces.
- Causes by adding electrolytes or mixing oppositely charged sols.
- Colloids can be precipitated.
Hardy-Schulze Rule
- Precipitation of a sol due to addition of electrolytes is dependent upon the valence of the precipitating ion. Higher valance ions will have a more significant precipitating power.
Additional Colloidal Properties
- DLVO Theory: Describe interaction, stability, and attraction/repulsion in lyophobic colloids.
- Potential Energy Curves: Showing van der Waals attraction and electrostatic repulsion between particles, influencing stability.
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Description
This quiz explores the concepts of dispersed systems, including molecular, colloidal, and coarse dispersions. Learn about the properties and examples of colloidal systems, as well as their phases and classifications. Test your knowledge on natural colloids and their applications in everyday life.
