SODIUM ALGINATE

SYNONYM: Algin, polymannuronate, Alginic acid.

BIOLOGICAL SOURCE:  It is the sodium salt of Alginic acid  which is prepared  from  the various species of brown marine algae of class Phaeophyceae.The sea weeds are obtained from Laminaria digitata, L.caustoni ,L.saccharina of the family Laminariaceae. The other sources of the alginates are species of the family Fucaceae, mainly Fucus serratus, F.vesiculosus etc.

GEOGRAPHICAL SOURCE: They will grow in the cold waters of the world. It is mainly produced on the coast of USA, Britain, Norway, Chile, China, Canada, Australia and South Africa.

COLLECTION AND PREPARATION: Brown Sea weeds are collected from the sea .The weeds are cut by hand or sickle is spread out and dried in the sun to about 12-17% moisture content. Dried ones can be stored for some period without degradation

Next, dried sea weeds are converted to powder by milling and macerated with dilute sodium carbonate solution .The paste mass obtained is further diluted with sufficient water to separate insoluble matter .From the clear liquid sodium alginate is precipitated by the addition of ethyl alcohol.

CHARACTERS:  Alginic acid is insoluble in hot water, slightly soluble in hot water. Sodium alginate is a white or yellowish powder, soluble in cold and hot water .The solution is not coagulated by heating and does not form a jelly on cooling.

CHEMICAL CONSTITUENTS: Alginic acid is a polyuronic acid composed of D-mannuronic acid and L-glucuronic acid. The chain length of Alginic acid varies according to the process isolation and source of raw materials.

IDENTIFICATION TESTS:

1. The aqueous solution of sodium alginate forms copious precipitate with

Calcium chloride solution.

2.1% solution in water forms heavy gelatinous precipitate with dilute sulphuric acid.

3. Alginate solution gives Fehling’s test positive only after hydrolysis with mineral acids.

USES:  It is used as stabilizing, thickening, gelling or deflocculating agent in pharmaceutical, food and cosmetic industries including creams, ointments, pastes, jellies and tablets.

                             Alginate fibres and gauze (consist of equal proportions of sodium alginate and calcium alginate) are used to produce absorbable haemostatic dressings.                  

                               Alginate wool is used as swabs in surgery. Alginate glove powder is prepared from the wool with the addition 1% boric acid.