Test for Sea Weed Extract (Contents of Alginic Acid)

A. REAGENT
a. 0.1M HCL
b. 0.1M CaCl2
c.0.1M EDTA
d.10% Triethanolamine, N (C2H4OH)3
e. AgNO3
f. Na2C2O4 solution
g. Calcium Crimson Indicators
B. STEPS OF MEASURATION
1> Dissolving 3.000g sample that of exact weighing into 50ml water.
2> Adding 60ml 0.2M HCL to acidify for 2 – 3 hours.
3> Sieve on 350mesh meshwork, washing the residue on sieve, and stop till no Cl - exist. (Test by AgNO3 solution)
4> Flashing the residue into beaker, together with 80ml 0.1M CaCl2 adding, and stirring, then filtrate by 350mesh meshwork after placed for 20 – 30min, washing the residue and stop till no Ca2+ exist. (Test by AgNO3)
5> Dunking the residue with 40ml0.1M HCL for 30min, then sieve on 350mesh meshwork, wash the residue by distilled water for 4 – 5 times, then collect the filtrate into conical beaker, and then regulate the PH Value to 12 by 10M NaOH solution with 0.5-1ml Triethanolamine adding.
6> Adding 5-6 drops of Calcium Crimson Indicator into the solution by using 0.01M EDTA titration, when the color of solution changed from tartaric red to bluish green, write down the wastage of EDTA (VEDTA).
7> Calculation: calculate the content of Alginic Acid as the expression below:
X(%) = CEDTAVEDTA × 0.194/m sample × 100%
Thereinto:
CEDTA -------------- Density of EDTA standard solution
VEDTA ----------------- Millilliter amount of EDTA solution
M sample -------- sample weight
0.194 ------------ Coefficienta