ALGINIC ACID TESTING METHOD.
 CHEMICAL FORMULA.
DEFINITION :
Alginic acid is a naturally occurring hydrophilic colloidal Polysaccharide
obtained from the various species of brown seaweed (phaeophyceae).
It is a linear copolymer consisting mainly of residues of b-1,4-linked
D-mannuronic acid and a-1,4-linked L-glucuronic acid. These
Monomersare often arranged in homopolymeric blocks separated by
regions approximateling an altetnating sequence of the two acid
monomers.
 METHOD OF ASSAY
Gravimetric method
Dissolve 0.500g of sample in 10ml of sodium hydroxide TS, add
90ml of water, and filter if necessary. Add 15ml of 4 N hydrochloric acid
100ml of 90% v/v ethanol. Allow this mixrure to stand for 2hr.,decant the
supernatant liquid as far as possible, and centrifuge. Decant the liquid and
replace it by 90% v/v ethanol to a fine glass filter, wash with dry acetone
place the filter in a vaccum deccucator, and dry to constant weight at
100◦C.
Calculate the percent purity of the sample by the formula:
%Purity = (200 × F × W) / % Dry substance in sample × 100
In which F is a conversion factor specified as 1.000 and W is weight (in
grams) of the dry precipitate.