Analytical Techniques - Biomass Gasification, Pyrolysis and Torrefaction - page 445

Cooling water out

Cooling water in

Thimble

FIGURE 13.1 Soxhlet extractor for the determination of extractives.

for drying ( Figure 13.1 ). Ethanol 200 proof, toluene (reagent grade), and tolue-
ne ethanol mixture (1:1 volume basis) are required as solvents.

The test Procedures:
a. Weigh the extraction thimbles and cover without sample and weigh
thimbles by adding 2 3 g of sample.

b. Dry thimbles in vacuum oven not exceeding 45 C for 24 h or to a con-
stant weight.
c. Thimbles are then cooled down to room temperature in a desiccator
for an hour and weighed.
d. Cooled thimbles are then kept inside the Soxhelt extraction units

( Figure 13.1 ).
e. Take 200 ml of ethanol toluene mixture in a 500 ml round bottom

flask with several boiling chips to prevent bumping.
f. Carry out the extraction with well-ventilated chemical fume hood for
2 h, keeping the liquid boiling. Ensure that the siphoning from the
extractor is no less than four times per hour.
g. After the extraction, take the thimbles out from the extractors to drain
the excess solvent.
h. Then wash the sample using ethanol and dry in the vacuum oven over
night at a temperature not exceeding 45 C for 24 h.