Two new ultrasound based techniques (acoustics and electroacoustics) offer
a unique opportunity to characterize concentrated dispersion, emulsions and
microemulsions in their natural state, without dilution. Elimination of th
e dilution protocol is crucial for an adequate characterization of liquid d
ispersions, especially structured. Dilution changes the thermodynamic equil
ibrium in these systems and affects their reological properties. Changes in
equilibrium conditions can lead to variation of the particle size and can
also affect surface chemistry. In this paper, a short review of the theoret
ical basis of the ultrasound techniques is given. Emphasis is placed on the
theoretical models which are supposed to be valid in concentrated systems.
These theories have been developed recently on the basis of 'cell model co
ncept' for both acoustics and electroacoustics. This approach opens the way
to implement particle-particle interaction into the theoretical model. Exp
eriment proves that these theories are adequate in concentrated systems up
to 45% vol. Second part of the paper is dedicated to the applications of ac
oustics; and electroacoustics. The list of applications includes: ceramics,
mixed dispersed systems, chemical-polishing materials, emulsions, food emu
lsions, microemulsions and latecies. (C) 2000 Elsevier Science B.V. All rig
hts reserved.