Peptization
The re- dissolution of a flocculated or coagulated colloid is referred to as peptization (Greek) . It is converted into a colloidal solution (sol).
The reverse process is known as coagulation or gel formation , whereby large agglomerates are created through the agglomeration of colloidal particles.
The coagulation of colloids or of coarsely dispersed systems such as suspensions can be prevented by adding peptizers . These are ions with a strong electrical charge such as citrates , tartrates , oxalates or diphosphates . They are adsorbed on the particle surface of charged particles and can overcompensate for their Nernst potential . This leads to a polarization reversal, i.e. a reversal of the sign of the electrical potential at the shear plane ( zeta potential ). This results in an electrostatic repulsion between the particles, which suppresses their agglomeration.
Peptizers are used as dispersants e.g. B. used in pharmaceutical technology ( galenics ) to produce stable suspensions.
In the case of easily soluble (lyophilic) colloids, peptization can also be achieved by dilution or by increasing the temperature.
Individual evidence
- ^ R. Voigt: Pharmaceutical technology. For studies and work. Deutscher Apotheker Verlag 2010, page 125.
- ^ R. Voigt: Pharmaceutical technology. For studies and work. Deutscher Apotheker Verlag 2010, page 469.
- ↑ KH Bauer, K.-H. Frömming, C. Führer: Pharmazeutische Technologie , Thieme Verlag 1989, page 232.