II) Determination of combined acidity
a) Weigh accurately about 10 g of material into a 250 mL flask.
b) Add enough dilute sulphuric acid to neutralize the alkalinity of the
material and provide 25 mL of the acid in excess.
c) Place the flask on a sand bath; put some glass beads in the flask to
prevent bumping. Attach an air condensor and boil for about one and
a half hours.
Regulate the heating so that though boiling is fairly vigorous, very little
evaporation takes place.
d) Agitate frequently during boiling, and at the end, wash the condensor
with water. Cool the contents of the flask.
e) Add 30 g of sodium chloride and 25 mL of ether followed by 5 drops
of methyl orange indicator.
f) Gently swirl the flask and titrate the mixture with standard sodium
hydroxide solution. Reserve this solution for testing total fatty matter.
g) Also carry out a blank determination using all reagents (except the
sample) and total quantity of dilute sulphuric acid used with the
sample including that used for neutralizing the alkalinity.