Then, 1.2g of ground sodium hexametaphosphate
was added and the pH was adjusted to 1.5 with
hydrochloric acid (0.5N), nitric acid (0.5N) or citric acid
respectively. Thereafter, the mixture was heated while stirred
continuously to 45, 65 or 90°C in a stirring hot plate for 60
minutes. Next, the pH was checked at intervals of 15 minutes
and the water loss was replaced except for the last 20 minutes.
The hot acid extract was filtered through filter funnel equipped
with two-layer of muslin cloth. For each acid, three different
ranges of temperature extract collected separately for further
experiments. The filtrate was cooled to 4°C.