**2.2 Molecular weight and solubility**

The molecular weight of sodium alginate ranges between 32,000 and 400,000 g/ mol on the commercial level. Alginate deals with a broad range of solubilities due to its different molecular weights [17]. The alginates are insoluble in water (H20) because it contains a terminal carboxylic ion (-COO-), so these cations make bonds to this and yield a not water-soluble product, and alginates with divalent or trivalent cations also are water insoluble [18]. Salts of alginic acid with monovalent cations, including Na-salt, K-salt, NH4-salt as well as propylene glycol alginate, are all soluble in hot and cold water. Sodium alginate is present within the cell wall of marine brown algae and contains 30 to 60% alginic acid approximately [19]. The transformation of alginic acid to sodium alginate permits its Solubility in water, which assists in its extraction. Alginate can absorb body fluids and H20 up to 20 times its weight, resulting in a hydrophilic gel.
