Flashcards in Dispersed Systems Deck (74)
fine particles, evenly distributed in a vehicle/dispersion medium
T/F In a dispersion system, the particles are NOT aggregated
What are the 3 types of dispersion systems?
-less than 1 nm
-generally can not be seen with the eye
-1 nm- 0.5 um
-greater than 0.5 um
In dialysis, the blood cells and plasma proteins fall in the ____ size and will be retained
What are the 3 types of colloidal systems?
loves the solvent (example water)
need special dispersion or condensation method
surfactants are an example of ____ colloids
-lowers the surface tension
-have a certain affinity for both polar and non polar solvents (does not allow water and oil to separate)
at a concentration that is characteristic of each amphiphile, these molecules will aggregate to produce____
micelles (hydrophilic on the outside and lipophilic on the inside)
critical micelle concentration
Critical Micelle concentration involves....
blocking the surface and adding surfactant passed the concentration leading to a micelle being formed
Colloids have properties such as ____, _____, and _____
What is an example of a natural colloid?
What is an example of a coarse dispersion?
T/F Suspension may be for oral, ophthalmic, parenteral, or topical use
advantages of suspension (4)
-greater flexibility in the administration
-can better mask the taste of the drug
-some drugs are more stable as a suspension
-drugs not soluble in common vehicles
What are the 3 desired features of a suspension?
-pour readily and evenly
-particle size should remain constant
-uniform dispersion/ settle slow
T/F The bigger the particle, the better it dissolves
factors involved in the rate of velocity of SETTLING of the particles in a suspension
T/F Stokes equation applies to uniform, perfectly spherical particles settling in a very dilute suspension WITH hindrance or turbulance
What are ways to slow settling in a suspension? (3)
-small particle size
-increase density of vehicle
-increase viscosity of vehicle
How can particles dispersed in a liquid media become charged? (2)
-selective adsorption of ionic species present in solution
-ionization of groups situated at the surface of the particle
The electrical double layer is known as the .....
Nernst and Zeta potential
T/F There is ALMOST ALWAYS charges surrounded by particle size particles in a suspension
11' is known as
nernst potential : true potential