Final Exam Pharmaceutics Ophthalmic Preparations 1. Define: a. Ophthalmic Preparation sterile solutions that are compounded and packaged for instillation into the eye. b. Isosmotic Having the same total osmotic pressure or osmolality as another fluid (ordinarily intracellular fluid); such a fluid is not isotonic if it includes solutes that freely permeate cell membranes. c. Isotonic a solution that has the same salt concentration as the normal cells of the body and the blood. d. Hypotonic a solution with a lower salt concentration than in normal cel ls of the body and blood. e. Hypertonic a solution with a higher salt concentration than in normal cel ls of the body and the blood. f. Crenation shrinking of a cell due to immersion in a hypertonic solution. g. Hemolysis bursting of a cell due to immersion in a hypotonic solution. 2. List the 5 factors which must be considered in preparing an ophthalmic preparation. Antimicrobial Preservatives, Isotonicity, Buffering, Viscosity, Packaging. 3. List the 3 key conditions necessary for steam sterilization. Temperature (121 C), Pressure (15 psig), Time (15-20 minutes). 4. List 6 preservatives and their usual concentration which are suitable for inclusion in an ophthalmic preparation. Benzalkonium Chloride (0.012%), Benzethonium Chloride (0.01%), Chlorobutanol (0.5%), Phenyl Mercuric Acetate (0.004%), Phenyl Mercuric Nitrate (0.004%), Thiomersal (0.01%) 5. Perform calculation to determine the: a. Freezing point of a solution of non-electrolyte 1.86 MW 0.52 X GM. b. Freezing point of a solution of an electrolyte c. Isotonic solution concentration of either an electrolyte or non-electrolyte given its freezing point depression (0.52)(MW) X Gm. Solute (1.86)(i) 1000 Gm Solution d. Sodium Chloride Equivalent for either an electrolyte or non-electrolyte E = MW (NaCl) x CX _ C(NaCl) MWx e. Dissociation constant for an electrolyte f. Quantity of a substance which should be added to an ophthalmic prescription in order to make it isotonic 1. Convert all conc. to weight.
1
g.
2. Multiply quantity of each ingredient by its Sodium Chloride equivalent. 3. Sum the quantity of Sodium Chloride equivalent contributed by all. 4. Determine the quantity of Sodium Chloride alone needed to prepare isotonic solution (0.9%) 5. Subtract 3 from 4. 6. Convert Sodium Chloride required to any other tonicity adjusting agent used (divide #5 (gm) by the substances Sodium Chloride equivalent). Volume of purified water needed to prepare an isotonic solution utilizing the WhiteVincent Method VT(H2O) = (Weight)(NaCl Eq.)(111.1) VT = Total volume of water required to prepare an isotonic solution W = weight of substance E = Sodium Chloride Equivalent for the substance
6. List 3 reasons for buffering an ophthalmic solution. Reduce patient discomfort, ensure drug stability, and control therapeutic activity of the drug 7. Give the elementary equation for kinematic viscosity. Kinematic Viscosity = Dynamic Viscosity Density 8.
Identify
the Ostwald Equation and each of the symbols used within the equation.
1 = (p1)(t1) 2 (p2)(t2) 1 = unknown viscosity 2 = viscosity of the standard 1 = density of the unknown liquid 2 = density of the standard t1 = flow time of the unknown t2 = flow time of the standard 9. Calculate the viscosity of an unknown solution given the finite parameters for the Ostwald Equation.
10. List 4 agents which are frequently used as thickening agents for ophthalmic preparations. Methyl cellulose 400 cps (0.25%), Methyl cellulose 25 cps (1%), Hydroxypropyl methyl cellulose (variable with product), Polyvinyl alcohol (variable with product).
Parenteral Products 1. List the 5 types of products designated as a parenteral. Small volume, large volume, irrigating solutions, dialysis solutions, biological products
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2. Define: a. Parenteral injectable route of administration. b. Pyrogen fever producing organic substances, from microbial biochemistry, which are responsible for patient febrile reactions following intravenous injections. c. Intravenous administered by injecting directly into a ve in. d. Intradermal administered by injecting directly into or in-between layers of the skin. e. Subcutaneous administered by injecting directly into the layer under the skin. f. Intramuscular administered by injecting directly within a muscle g. Biological pharmaceutical products administered by injection for the diagnosis, treatment or prevention of disease. (vaccines, antitoxins) h. Ampul uni-bodied glass containers which are sealed by fusion under aseptic conditions after filling and once opened cannot be resealed. 3. List the 5 reasons why the parenteral route of drug administration is used. Emergency situations, uncooperative patients, unconscious patients, patient unable to accept or tolerate medication via the oral route, drug is ineffective or unabsorbable by any other route 4. List the 3 sites which are used for IM injections. Gluteus maximus, deltoid muscle, mid-lateral muscle of the thigh 5. List 7 possible patient injuries which may be caused by an IM injection. Hematoma, skin sloughing, scar formation, nerve damage resulting in paralysis, cysts, abscesses, emboli 6. List 3 reasons for using the ID route of injection. Diagnostic tests, desensitization injections, immunization 7. List 4 common sites used for SQ injections. Tissues of the arm, forearm, thigh, buttocks 8. List 3 possible problems caused by the SQ injection of irritating thick drug suspensions. Induration (hardening of an area of the body as a reaction to inflammation, hyperemia, or neoplastic infiltration), sloughing of tissue, abscess formation (all produce pain at site) 9. Differentiate between the following solvents and vehicles used for injection: a. Water for injection Pyrogen free, used in the preparation of injectable or other products which will be sterilized after preparation, must be used within 24 hours following production and collections, stored in sterile, Pyrogen free glass container. b. Sterile water for injection water for injection that has been sterilized, packaged in single dose containers >1000ml, must be Pyrogen free, may not contain antimicrobial agents, intended for use as a solvent, vehicle, or diluent for sterile prepackaged drugs. c. Bacteriostatic water for injection sterile water for injection containing 1 or more antimicrobial agents, packaged in container >30 ml, used as a sterile vehicle for small volume injections, label and state the names of antimicrobials used.
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d. Sodium Chloride injection sterile isotonic solution of NaCl in water for injection, contains no antimicrobials, used as sterile vehicle for preparing parentally admin drugs. e. Bacteriostatic Sodium Chloride for injection a sterile isotonic solution of NaCl (0.9%) in water for injection containing 1 or more antimicrobials, packaged in >30 ml. f. Ringers Injection sterile solution of NaCl (860mg), KCl (30mg), CaCl2 (33mg), and sodium lactate, used as a fluid and electrolyte replenisher and system alkalinizier. g. Lactated Ringers Injection - is a sterile, nonpyrogenic solution containing isotonic concentrations of electrolytes in water for injection. It is administered by intravenous infusion. NaCl (600mg), sodium lactate anhydrous (310mg), KCl (30mg), and CaCl2 dihydrate (20mg). 10. List 4 characteristics of a non-aqueous vehicle which may be chosen as a parenteral vehicle. Non-toxic, non-irritating, non-sensitizing, non-therapeutic itself 11. List the 6 physical characteristics which may permit non-aqueous vehicle use in a parenteral product. Reasonable viscosity to allow for the ease of injection, fluidity ove r a wide temperature range, sufficiently high boiling point to permit heat sterilization, miscibility with body fluids, low vapor pressure to avoid problems arising during heat sterilization, ease of purification and standardization in order to obtain a constant purity 12. List the 3 categories of non-aqueous vehicles and 2 examples of each category. i. Fixed vegetable oils sesame or peanut ii. Water miscible alcohol or glycerin iii. Water immiscible ethyl Oleate, Isopropyl Myristate 13. List the 5 general methods which are used for the sterilization of pharmaceutical products. Steam, dry heat, gas, sterilization by filtration, sterilization by ionizing radiation 14. List the 7 types of products included under the definition of biological. Vaccines, toxins, toxoids, blood derivatives, antitoxins, diagnostic aids, immune serums 15. Define the following terms: a. Immunity resistance of an organism to infection, disease, or other unwanted invasion. b. Natural/Native Immunity immunity that is naturally present and not due to prior sensitization to an antigen. c. Acquired Immunity immunity acquired by infection or vaccination or by the transfer of the antibody or lymphocytes from an immune donor. d. Active Immunity the production of antibodies against a specific agent by the immune system. Can be acquired by either contracting an infectious disease or by receiving a vaccination. It is usually permanent so you are protected the rest of your life. e. Passive Immunity immunity produced by the transfer to one person of antibodies that were produced by another person. This diminishes in a relatively short time, usually a few weeks or months. f. Vaccine microbial preparation of killed or modified microorganisms that can stimulate an immune response in the body to prevent future infection with similar microorganisms. This is usually delivered by injection.
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g.
Toxoid - a bacterial toxin whose toxicity has been weakened or suppressed either by a chemical or heat treatment without eliminating its capacity to stimulate the production of antitoxins by the immune system. h. Toxin one of a number of poisons produced by certain plants, animals, and bacteria. i. Antitoxin an antibody capable of destroying microorganisms including viruses and bacteria. It provides passive immunity. j. Antiserum human or animal serum containing antibodies that are specific for one or more antigens. k. Human Immune Serums and Globulins - Human immune serum globulin (H ISG) is prepared from human serum. Special treatment of the serum removes various undesirable proteins and infectious viruses, thus providing a safe product for intramuscular injection. 16. Define the following terms: a. Irrigation solution solutions which are intended to bathe or wash wounds, surgical incisions, or body tissues. b. Dialysis a process of substance separation using the method of diffusibility through membranes, filtering blood through a semi-permeable membrane to remove waste. c. Peritoneal Dialysis the removal of biologically toxic substances normally excreted by the kidney via the peritoneal cavity. This technique uses the patient's own body tissues inside of the belly (abdominal cavity) to act as a filter. The intestines lie in the abdominal cavity. A plastic tube called a "dialysis catheter" is placed through the abdominal wall into the abdominal cavity. A special fluid is then flushed into the abdominal cavity and washes around the intestines. The intestinal walls act as a filter between this fluid and the blood stream. By using different types of solutions, waste products and excess water can be removed from the body through this process. d. Hemodialysis the process of removing toxins from the blood and restoring normal constituents of it.
Colloidal and Surface-Chemistry Aspects of Dosage Forms 1. Describe the 5 common types of colloidally dispensed particles which exist i n nature. A three-dimensional solid particle or liquid droplet, a thread or rod-like particle or filament, a sheet or plate-like particle, a biological membrane 2. Distinguish between crystalloids and colloids by usi ng both definition and example. Crystalloids are substances with high rates of diffusion in water and are readily dialyzed through membranes (salts and sucrose). Colloids do not crystallize, however, they diffuse ver y slowly in water but do not pass through a dialysis membrane (gelatin, starch, gums, tannins, Prussian blue). 3. Provide dialogue as to the contributions of the following scientists to the field of surface chemistry and colloid technology: a. Thomas Graham distinguished between crystalloids and colloids, coined the words Sol, Gel, Peptization, and Syneresis, and saw colloids by the Tindall Effect.
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st
b. Wolfgang Ostwald published the 1 edition of the Kolloid-Zeitschrift, devoted entire career to colloids, wrote a booklet entitled The World of the Neglected Dimension which pointed out the difference between solutions of small molecules and ions (molecularly disperse systems), coarse dispersions which readily settle, and colloidal dispersions which occupy an intermediate position. c. Von Weimarn demonstrated that there are no intrinsically colloidal substances. Most substances can be prepared in colloidal state, during the process of dissolution and precipitation all systems pass through the colloidal size range. d. Ubbelohde e. Cannon and Fenske f. Stoke - His work on fluid motion and viscosity led to his calculating the te rminal velocity for a sphere falling in a viscous medium. This became known as Stokes' law. g. Vant Hoff recognized the relationship between osomotic pressure, concentration and temperature. He presented the Vant Hoff equation to establish this relationship for very dilute solution. h. Freudlich established an equation that relates the concentration of a solute on the surface of an adsorbent to the concentration of the solute in the liquid with which it is in contact. i. Langmuir developed an equation to characterize the complete adsorption isotherm. j. J. Willard Gibb derived an equation to deal with molecules which accumulated in the surface layer and lowered the surface tension. 4. List 2 or more examples of rheologys importance in the following areas: a. Physiology blood flow (blood cant be too thick or thin), stressing of muscles and deformation of boney structure. b. Pharmaceutical Manufacturing Operations stirring, mixing, compressing and compacting, filling containers, extruding. c. Pharmaceutical and Cosmetic products flow through a hypodermic nee dle, pouring from the bottle, spreading of an ointment on the skin, squeezing a paste from a tube. d. Packaging Materials strength and toughness of bottles and wrapping films, deformability of rubber stoppers and tubing. 5. Evaluate the characteristics of the following systems: a. Solids have constant volume & permanent shape, and are capable of supporting a load b. Liquids have variable shape & constant volume at constant temperature at all but very high pressure but support no l oad. c. Gases have neither constant volume nor permanent shape. 6. Describe the load or stress in appropriate dimensional form and in unit form. Loads have the dimensions of force per unit area and t he units: Dynes = Gm. * cm. = Gm. __ 2 2 2 2 Cm sec * cm cm * sec 7. List the 5 different types of deformation or strain produced by stress. Tension, bending, torsion (twisting), compression, shearing (karate chop) 8.
Identify
Hookes Law and the symbols used in this expression.
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= L/L
where is the strain or elongation
Hookes Law is T = E * where E is the Hookes Law Constant and T is the tensile stress Or F/A = E * (L/L) 9. Define the terms: a. Stress an applied force or system of forces that tends to strain or deform a solid b. Strain deformation due to stress (elongation ect.) c. Elasticity a characteristic property of solids representing their stiffness or hardness; the ability of a solid to return to its orig inal shape after being subjected to strain. d. Toughness the energy required per unit volume of material to cause ruptures and is represented by the area between the stress-strain curve and the strain axis. 10. Identify the equation which represents viscosity, the symbols used in the equation, and the units in which viscosity is expressed. Viscositys () unit is poise and is represented by the following:
=
T/
=
(F/A) 1/t
T = shear stress =
dyne/cm 1/sec
=
= rate of shear
Gm*cm*sec sec2*cm*
=
Gm._ cm*sec
11. List the 2 mechanisms upon which devices operate to measure viscosity. The flow of a liquid through a capillary tube and the flow of a liquid between two concentric cylinders 12. Identify Poiseuilles Law and the symbols used in this equation. = (R4P/8L)*(t/V) R = radius of the capillary L = length of the capillary P= pressure difference 2 V/t = rate of flow (cm /sec) If P = hdG = (liquid column height)(density)(gravity) then: 4
= (R havG/8LV)(td) = Ktd And if K is known then the viscosity can be determined Using this equation and comparison to a standard will yield:
1 2
=
(p1)(t1) (p2)(t2)
1 = unknown viscosity 2= viscosity of the standard P1 = density of the unknown liquid P2= density of the standard T1 = flow time of the unknown T2= flow time of the standard 13. Evaluate the various bob and cup viscosimeters as to thei r efficiency. Bob = inner cylinder Cup = outer cylinder closed at the bottom
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Stormer Viscosimeter measures the rate of shear as a function of the spee d of rotation of the bob. Haake Viscosimeter and Drage Viscosimeter rate of shear is fixed at a selected value and stress is measured by a torsion spring on the bob s haft Merrill-Brookfield measures stress by a strain gauge on the cup. Hercules Hi-Shear Viscosimeter measures stress by a spring on the cup MacMichael Viscosimeter cup is rotated at one of several fixed speeds and the stress on the bob is measured by the angle of twist on the torsion wire suspending the bob. 14. Identify the equation used by rotational instruments to measure viscosity and the symbols used in this expression. T
= ((4RcRb)/(Rc Rb))*(h W) T = torque in (dyne-cm) h = bob height Rc = radius of the cup Rb = radius of the bob W = rate of rotation (radius/sec)
15. List the 2 factors upon which viscosity depends (in Newtonian Liquids?). Composition of the liquid and temperature 16. Define the terms: a. Viscosity the reciprocal slope of the consistency curv e; a measure of the resistance of a fluid which is being deformed by either shear stress of extensional stress. In general it is the resistance to flow b. Fluidity the reciprocal of viscosity, measured by the s lope of the consistency curve; the physical property of a substance that enables it to flow. c. Shear Stress a form of stress that subjects an object to which force is applied to skew, tending to cause shear strain. For example, shear stress on a block of wood would arise by fixing one end and applying force to this other; this would tend to change the block's shape from a rectangle to a parallelogram. (tangential forces) d. Rate of Shear - The change in velocity of parallel planes in a flowing fluid separated by unit distance; its units expressed in seconds-1. e. Elasticity property of solids; they deform under stress but once the stress is removed, they regain their original shape and the strain returns to zero. f. Plasticity - generally means ability to permanently change or deform. ( It differs from "elasticity", which refers to ability to change temporarily and rev ert back to original form.); cannot recover its shape g. Diffusion Net transport of molecules from a regi on of higher concentration to one of lower concentration by random molecular motion. The result of diffusion is a gradual mixing of material. 17. Evaluate the effect of temperature on viscosity using equations and dialogue. The viscosity of liquids decreases exponentially with increasing temperature.
= AeE/RT or Log = Log A + (E)R/2.303T E = apparent activation energy for viscous flow
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R = gas constant T = absolute temperature A = constant 18. List 4 systems which are capable of providing viscosity. Solutions of polymers, gums, solutions of fine solids in water, and solutions of fine solids in non-polar solvents 19. List the 3 factors which can deter mine the viscosity of a polymer solution. Concentration, salvation of the dissolved polymers, and chain length 20. Describe the parameters which can reduce the viscosity of a polymer solution. Polymer chains elongate and offer less resistance to flow, the amount of water trapped within the coils decrease and lowers flow, as intermolecular entanglements decrease the amount of work required to break the remaining entanglements is also reduced. 21. Draw and describe the consistency curve for the following types of viscosity systems: a. Newtonian liquids whose viscosity depends only on the composition of the liquid and temperature. The flow curves are obtained by plotting Rate of Shear versus shear stress (torque) scale divisions or angular deflection. b. Pseudoplastic at extremely low shear rates the systems exhibit Newtonian flow behavior, at extremely big rates of shear the particulate aggregates cannot break up any further and hence cannot decrease the viscosity any further, at intermediate rates of shear the viscosity is constantly changing as the aggregates are breaking up under higher rates of shear. c. Plastic d. Thixotropic e. Dilatants f. Electroviscous Effect 22. List 8 or more substances which demonstrate yield stresses. Pastes, gels, ointments, putties, creams, salves, butter, modeling clay, margarine, dough, mayonnaise 23. Identify Einsteins Viscosity Equation and the symbols used in this expression. 24. List the 6 assumptions made for the validity of the Einstein Equation. 25. Derive Stokes Law from the expression: Driving Force = Opposing Force. (4/3)R3(dp-d1)g = 6 RV 2 V = terminal velocisty = 2R (dp-d1)g 9
26. List the 4 processes which a molecule may flow through a barrier. Simple molecular permeation, movement through pores or channels between the cells, dissolution of the molecule into the bulk membrane, passage through solvent pores of the membrane 9
27. List the 3 factors upon which the diffusional process is dependent. Solubility of the drug in the membrane, size and shape of the molecules, and size and shape of the pores and channels 28. Identify the vant Hoff Equation and the symbols used in this expression. V = nRT = Osmotic Pressure V = Volume of Soltuion n = number of molecules of solute R = Gas constant T = Absolute Temperature 29. Identify the Modified vant Hoff Equation and the symbols used in this expression. _ _ = (RT/V) + B*C C C = Concentration in Gm./cm of solute B = TRA2, where A2 is the second real coefficient which expresses deviation from real behavior 30. List the 4 effects which can occur when light passes through a medium. Transmitted, Absorbed, Refracted, or Scattered 31. Identify the equation which defines turbidity as well as the symbols used in this equation. I/I0
- L
e ¨ and = (2.303/L)*(Log I/I0) I0 = Intensity of incident light I = Intensity of transmitted light L = length of the optical path of the cell =
= Turbidity
32. List the 3 negative attributes of a material which prohibits its use with light scattering techniques. Absorb or reflect light, fluoresce, or are colored 33. Define the following terms: a. Adsorption the accumulation of a substance at a surface or interface (membrane, enzyme, cell wall) b. Absorption the accumulation and distribution of a substance throughout a phase, sponge-like (tissues, organs, blood) c. Adsorbent the solid d. Adsorbate the substance being adsorbed 34. Identify the Freudlich Equation and the symbols used in this expression. m (x/m) = Kc and Log (x/m) = Log K + (1/n)Logc (sorbate/adsorbant) 35. List the 2 disadvantages when using the Freundlich Equation. 10
The dimensional value of K depends upon the value of (x), and the equation does not account for the possibility of (x/m) increasing indefinitely with (c). 36. Draw and label the axis of a theoretical Freundlich Isotherm and describe the limitation of this plot. The plot of Log(x/m) versus Log (c) gives us the Log-Log relationship which is linear and easily handled. 37. Identify the Langmuir Equation and the symbols used in this expression. (x/m) = (x/m)mono b*c 1 + bc B = a constant related to the heat of adsorption (x/m)/(x/mmono) = the degree of coverage of the adsorbent by the sorbate C = the concentration of drug 38. Identify the linear form of the Langmuir Equation. (c)_ = 1 = c___ (x/m) (x/m)mono b (x/m)mono 39. Draw and label the axis of a theoretical Langmuir Isotherm and describe the limitations of this plot. It is plotted as the dependent variable y = c/(x/m) and the indepenedent variable x = c. This yields an intercept of (1/(x/m)mono b) and has a slope of (1/(x/m)mono). 40. Identify the equation which describes surface free energy, the symbols used in this expression and the units of surface tension. Surface free
=
= (W/A) or W = ()*(A) 3 W = work required to increase surface area per cm A = the increase in surface area observed
41. Identify the Young-Dupre Equation and the symbols used in this expression.
SA
= SL + LA cos SA = solid/air interfacial tension SL = solid/liquid interfacial tension LA = liquid/air interfacial tension = contact angle
42. Identify the Critical Surface Tension Equation and the symbols used in this expression. Cos
= 1 + b (c LA) B = a constant
c= the critical surface tension 43. Identify the Gibbs Adsorption Equation and the symbols used in this expression.
=
(C/RT)*(d /dC) =
(1/2.303RT)*(d/dLogC)
44. Draw and label the axis of a theoretical Gibbs Isotherm and describe the 3 types of curves . 11
45. Evaluate the properties of a Lyophobic Colloidal System which characterize these systems. These systems are solvent-hating dispersions which are intrinsically unstable, once prepared they must be stabilized by special additives, theses dispersions have low relative viscosities even at high concentrations (because of low salvation of the particles, low attraction between particles, and high repulsion), these systems produce high light scattering and strong Tyndall beams, and at high concentration Lyophobic systems become pastes. 46. List the 4 methods which can be used to prepare a lyophobic colloidal system. Comminution on Dispersion Mills, Ultrasonics, Electric arcs inside the liquid, Condensation and Precipitaion 47. Describe the process of condensation and precipitation as well as the conditions necessary to produce the colloid. Occurs in two steps: Nucleation (seeding of the solution) and particle growth Conditions necessary to produce the colloid: concentrated solution with high supersaturation where small particles form due to the l arge number which forms, and dilute systems with low supersaturation where large particles form due to few nuclei and low concentrations 48. Evaluate the process of particle attraction as it is used to stabilize a colloidal system. Particle attract due to Van der Waal forces operating over short distances, the t otal attractive forces between colloidal particles is the sum of the energies of attraction of nd rd each atom or ion, energy falls off only at the 2 or 3 power of interparticle distance, suspended particles may stick together when their interparticle distance comes within close range and causes them to coagulate into coarse flocs or grains 49. Evaluate the electric charge effect, with the aid of appropriate graphs, as it is used to stabilize a colloidal system.
50. List the 3 factors upon which the velocity of migration of a colloidal particle in an electric filed depends. Density of the surface charge (surface potential), thickness of the double layer, and viscosity of the medium 51. Identify the Smoluchowski Equation and the symbols used in this expression.
= (4/) * (L/E) * v = 13 v * (L/E) = viscosity = dielectric constant of the dispersion medium E = voltage L = distance between electrodes (in cm) V = velocity of migration (microns/sec) 13 = constant for water at 25 C when is in millivolts
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52. Define the following terms: a. Zeta Potential the electrical potential measured at the place of shear (the boundary between the bound and free water) surrounding the particle. b. Isoelectric Point exists when the Zeta potential is zero. c. Zero Point of Charge same as Isoelectric point. d. Brownian Motion continuous erratic motion of colloidal particles suspended in a liquid resulting from the continual bombardment by surrounding molecules. 53. List the 4 mechanisms which can impel particles toward each other. Brownian motion, convection currents, stirring, and gravitation force 54. Evaluate the effects which occur as distance betwe en particles diminishes using the symbols: ds (secondary energy distance): dp (primary energy distance): and db (maximum barrier energy). As the distance (d) decreases between particles then: ds the secondary energy become minimum and can account for deflocculation or peptization possibilities if the value is small and flocculation or aggregation if the value is large. dp the primary energy minimum which corresponds to a very strong attraction betwe en particles and accounts for the process of coagulation. db the maximum energy barrier which causes electrostatic repulsion of the particles. 55. Explain the D-L-V-O Theory as it applies to hydrophobic dispersion coagulation. Predicts the minimum concentration of salt required for coagulation is the inverse sixth power of the valence of the counter i on and the minimum coagulation concentration of salts with mono-, di-, and trivalent counterions should be in the ratio: 6 6 6 (1/1 ) = 1 = 100, (1/2 ) = 0.01562 = 1.562, (1/3 ) = .0013717 = .13737 56. Explain the Schultz-Hardy Rule as it applies to dispersion coagulation. Describes the dependence of the minimum salt concentration for coagulation on the valence of the counter ion. 57. Explain Traubes Rule as it applies to dispersion coagulation. The minimum coagulation concentration for a homologous series of surfactants decreases on ascending the series and parallels the increases in surface activity and Van der Waals attractive forces. 58. Define the terms: a. Lyophilicity the tendency of particles, surfaces, or functional groups to become excessively wetted, solvated, swollen or dissolved by solvents. b. Lipoplilicity the affinity for solvents of low polarity marterials. c. Gels formation of a continuous network or scaffolding of the dispersed solid phase throughout the entire liquid which solidifies. Posess high degrees of elasticity and can undergo considerable reversitble deformation. d. Magma any crude mixture of mineral or organic matters in the state of a thin paste. e. Jelly - A soft, semisolid food substance with a resilient consistency. f. Milk 59. List the 2 properties necessary for gel formation.
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The particles must be extensively solvated, and the particles must adhere to each other at the points of contact 60. Describe the 6 techniques which are used t o cause gelation and liquefaction. 1. Interparticle attraction occurs with particulate colloids with high surface-tovolume ratios and strong interparticle attractive force. Formation of continuous networks of flocculated particles held together by hydrogen bonding in the areas of contact. 2. Phase separation of polymers precipitation is caused by temperature fluctuations to produce solidification of the mixture (aqueous gelation solutions). 3. Polymer precipitation by non-solvent liquids this is caused by the addition of solvents miscible with the polymer solvent but is a non-solvent for the solute itself (addition of ethanol to polyelectrolytes). 4. Salting out. 5. Chemical reactions forming precipitates. 6. Syneresis elimination of water from the gel causing the structure to shrink. 61. List the 2 storage requirements for Milk, Magmas, and Inorganic Gels and Jellies. Store in tight containers, and requires a Shake well before using label.
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