Gele

Gels are finely dispersed systems of at least 2 phases:

• liquid/solid - a solid, finely dispersed substance and a liquid - usually water (lyogel)
• gaseous/solid (xerogels). Xerogels are obtained by removing the mechanically held liquid phase.

In gels, the solid disperse phase is present as a coherent three-dimensional framework in which the liquid or gaseous phase is enclosed. Both phases penetrate each other completely, i.e. they behave bicoherently.

There are different types of gel:

• Anhydrous oleo gels (oleogels): They generally consist of liquid paraffin with polyethylene or fatty oils.
• Hydrogels (hydrophilic gels): They consist of water, glycerol or propylene glycol.

Various substances serve as gel formers:

• Animal gel formers (gelatine)
• Vegetable gel formers(agar, alginates, carrageenan, pectins, quince seeds, wheat starch
• Mineral gel formers: Magnesium aluminium silicates
• Synthetic gel formers: polyacrylic acid, methylcellulose, polyvinylpyrrollidine, polivinyl alcohol

Gels are used either as cosmetic or pharmaceutical carrier media for ointments and creams. They also serve as hair gels for forming a hairstyle.