Gels and Magmas Flashcards
examples of colloidal dispersions
gels
magmas
colloidal dispersion
particle size: 1nm - 10um
colloidal dispersions are formed by addition of
gelling agent
single phase gel
macromolecules are distributed evenly across vehicle
large organic molecules
two phase gel (magma)
consisting of floccules of small particles
small inorganic particles
Tyndal effect
particles in a colloidal dispersion are small enough to be dispersed evenly and maintain a homogenous appearance
large enough to scatter light
clear gel
soluble ingredients
cloudy (turbid) gel
insoluble ingredients
gels
semirigid system
movement of diapering medium is restricted by crosslinking
gels are mostly ______________ due to increased ________________
aqueous preparations
viscosity
natural gelling agents
acacia
tragacanth
alginic acid
starch
synthetic gelling agents
carbomer
ethylcellulose
methylcellulose
carboxymethylcellulose
vehicle for gels
water
alcohol
propylene glycol
do gels need preservatives?
yes
colloid
substance dispersed through another substance
lyophilic colloids
solvent loving
good stability
large organic molecules
lyophobic colloids
solvent hating
inorganic particles
do not spontaneously disperse
ampiphillic colloids
may or may not be solvated
which colloids have increased viscosity when solute is increased?
lyophilic and amphiphillic
thixotropic gels are an example of
lyophilic colloids
classifications based on dispersed phase
inorganic gels
organic gels
classifications based on dispersing phase
hydrogels
organogels
alcogels
dispersing phase is alcohol
jellies contain a high proportion of
liquid (water)
jellies are formed by adding a ___________ such as ____________
jelling agent
tragacanth and carboxymethylcellulose
do jellies need preservatives?
yes
jellies should be stored
in a tight closed container
label for magmas and gels (liquid dosage form)
shake before use
____________ compounds need a wetting agent
inorganic
