Coarse Dispersion Flashcards
Emulsion types
O/w, w/o, multiple emulsions
Emulsifying agents that adsorbed at oil-water interfaces to form monomolecular films and reduce interfacial tension
Surface-active agents
Emulsifying agents which form a multimolecular film around the dispersed droplets
Hydrophilic colloids
Emulsifying agents which are adsorbed at the interface between two immiscible liquid phases and form what amounts to a film of particles around the dispersed globules
Finely divided solid particles
Polar non polar nature of the emulsifying agent
Hydrophile-Lipophile Balanch
Results from the flocculate and cocentration of the globhesf kf of internal pbase
Creaming
Concentration of the internal phase above which the emulsifying agent cannot produce a stable emulsion of the desired type
Critical point
Motion of the entire volume of emulsion in the field due to the pressure exerted by the immersion objective on the cover glass, evaporation of the continuous phase, or convection currents from heating by light source
Field flow
Indicates the relative change in conductivity between two cycles
Stability Index
Consists of large or swollen micelles containing the internal phaae
Microemulsions
Coarse dispersion in which insoluble solid particles are dispersed in liquid medium
Suspensions
T/F there is an inc in surface free energy as the particle size increases
F dec dapat
T/F inc size will lead to an inc in surface potential
F
Weakly bonded, settle rapidly, do not form cake
Flocculated suspension
Used to describe the settling of flocculated suspension
Subsidence
Ratio of the sedimentation volume of the flocculated suspension to the sedimentation volume of the suspension when deflocculated
Degree of Flocculation
Sheer thinning property of these vehicles facilitate re-formation of a uniform dispersion once shear is applied
Structured vehicles
Can be ascertained by observing the contact angle between the powder and the surface of the liquid
Wettability
Sulfur, Charcoal, and magnesium stearate
Hydrophobic
Zinc oxide, talc and magnesium carbonate
Hydrophilic
Added to retard sedimentation of flocs
Suspending agents
Produce flocs that are compatible with negatively charged suspending agents
Anionic electrolytes
Acts as flocculating agents by reducing the electric barrier between the particles, as evidenced by a decrease in zeta potential and the formation of a bridge between the adjacent particles so as to link them together in a loosely arranged structure
Electrolytes
Decreases the interfacial tension between solid prticles and liquid vehicle, facilitates wetting and deflocculation
Surfactants
Produce flocs that are compatible with negatively charged particles
Anionic electrolytes
Thermodynamically unstable system
Emulsions
Significant increase in the viscosity of dispersion
Auxillary effect
