Chemistry Reference
In-Depth Information
physical process that might be used to ''break'' a stable crude oil microemul-
sion resulting from the use of an anionic surfactant/medium chain length
alcohol extraction system.
5.4. A newly hired technician was given the job of formulating a simple O/W
emulsion for use as a vehicle for a topical antibiotic. After due consideration
of the inactive components in the cream, the technician decided to use an
alcohol-(POE)
5
surfactant that worked well at ambient temperature. However,
a sample of the emulsion was left near a radiator and the technician noted a
significant change in the viscosity of the warmed emulsion. When cooled
down, the sample returned to normal. What might have been happening in the
sample to cause the observed changes in the emulsion?
5.5. An O/Wemulsion using a soap surfactant was found to invert to a W/O system
on the addition of AlCl
3
. Propose an explanation for the observed change.
5.6. A concentrated surfactant solution containing a hexagonal close-packed meso-
phase would be appropriate for solubilizing which of the following materials
in the discontinuous phase: butyl myrstate, n-decanol, or lecithin.
5.7. A system of unilamellar vesicles is formed in an aqueous solution with pH 5. If
the average diameter of the vesicles is 25 nm, how many protons will be
encapsulated in the average vesicle core.
5.8. A vesicle system prepared with purified soybean lecithin in 1 mM KCl has an
inner radius of 15 nm. The system is then diluted with a large excess of
distilled water. Estimate the time required for the encapsulated ions to transfer
into the outer continuous phase given that the permeability coefficient for both
ions is 10
11
cm/s and that the dimensions of the vesicles do not change
despite the change in osmotic pressure.
5.9. Of the three classes of polymerizable lipids suggested for vesicle work in Figure 5.6,
which would probably be most suitable for a polymerization using UV radiation when
the internal phase contains a polyunsaturated fatty acid component? Why?
