Salts of alginate

Algin occurs in all members of the class Phaeophjceae, brown seaweed, as a stmctural component of the cell walls in the form of the insoluble mixed calcium, magnesium, sodium, and potassium salt of alginic acid. 

This is composed of the sodium and ealeium salts of alginic add formed into a powder or fibrous material and sterilized by autoelaving. It aids clotting by forming a sodium-caldum alginate complex in contact with tissue fluids, acting principally as a mechanical haemostat. It is relatively slowly absorbed and some residues may occasionally remain in the tissues. 

The molecular weight of the sodium salt of alginic acid has been determined by measurements of osmotic pressure in sodium chloride solution.88 The n/C versus C curve was found to be independent of salt concentration for values between 0.2 N and 0.5 JV, and the slope of the curve was the same for a series of seven fractions with values of molecular weight between 48,000 and 186,000 (220-860 D-mannuronic acid units). Intrinsic viscosity measurements showed the coefficient a in the modified Staudinger s equation88 to be 1.0 and the approximate value of Km to be 15(10)-4. 

In this experiment you will work with a natural polymer called alginic acid that comes from seaweed. Alginic acid is a polysaccharide as are cellulose and starch. Unlike cellulose and starch, however alginic acid as the name implies contains acidic functional groups called carboxylic acids. Salts of alginic acid are used as food additives, especially as a thickener. 

Salts of alginic acid which are capable of binding 200-300 times their own volume of water. They are added as swelling agents to explosive mixtures in order to improve their resistance to moisture, and to -> Slurries to increase viscosity. 

Calcium Alginate occurs as a white to yellow, fibrous or granular powder. It is the calcium salt of alginic acid (see the monograph for Alginic Acid). It is insoluble in water, but it is soluble in alkaline solutions or in solutions of substances that combine with the calcium. It is insoluble in organic solvents. 

Ammonium alginate is the ammonium salt of alginic acid. 

Sodium alginate consists chiefly of the sodium salt of alginic acid, which is a mixture of polyuronic acids composed of residues of D-mannuronic acid and L-guluronic acid. 

An expression has also been derived from the linear charge model for the enthalpy change when a polyelectrolyte is mixed with a salt solution containing the same counterion. (18) We have now investigated the enthalpy of mixing of alkali metal salts of alginate and dextran sulphate with solutions of alkali metal chlorides to establish whether the cation has any influence on the enthalpy change. 

Since only the sodium and potassium salts of alginic acid are soluble in water, the first aim of the extraction process is to convert the insoluble calcium and magnesium salts into sodium alginate. If the seaweed is treated with alkali, then the process necessary for extraction is an ion exchange ... 

Alginate is the generic name given to the salts of alginic acids. Alginic acids are polyuronides, i.e., polysaccharide molecules which are built up of uronic acid residues, molecules with a carboxyl group on the carbon that is not part of the ring [9]. 

Definition Purified carbohydrate prod, extracted from brown seaweed sodium salt of alginic acid... 

Classification Hydrophilic colloid Definition Ammonium salt of alginic acid Empirical (C6H706NH4)n... 

Definition Calcium salt of alginic acid Empirical (Ci2Hi4CaOi2)n Formula [(C6H706)2Ca]n Properties Wh. or cream-colored powd. or filaments, si. odor and taste sol. in alkaline sol n. insol. in water, acid, org. soivs. m.w. 195.16 Toxicology LD50 (IP, rat) 1407 mg/kg, (IV, rat) 64 mg/kg poison by IV route mod. toxic by IP route TSCA listed Precaution Flamm. 

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