Uronic acid, which is a constituent sugar of alginic acid, has one carboxyl group per unit with a high ion exchange property.
Binding with various cations generates unique alginate salts.
Alginic acid ion-exchanges not only with metal cations such as K+ but also with ammonium ions (NH4+) to make alginate salts.

Ammonium alginate, like sodium alginate, dissolves in cold and hot water to form a viscous aqueous solution, and gels when in contact with polyvalent cations such as Ca2+.

A characteristic of ammonium alginate is that it does not contain metal ions such as sodium so it has a low ash content.