The
method is now applicable to compounds with which previously low
results were obtained.
The substance is weighed into a small tube 24 mm. long and 11 mm.
wide, and is then introduced into the decomposition flask, which
contains 6 to 8 grms. of chromic acid, care being taken that the
chromic acid does not come into contact with the substance under
analysis. The decomposition flask is fitted with a thistle funnel, and
is connected to the reversed condenser and apparatus shown in the
figure. Fifty c.c. of concentrated sulphuric acid are run into the
flask. During the whole of the operation a gentle current of air (free
from carbon dioxide) is passed through the apparatus. The asbestos
plate underneath the flask is then warmed, and thus the flask and
contents are warmed by radiant heat from the plate alone until the
sulphuric acid darkens. At this point, where decomposition of the
organic substance begins, the flame is entirely removed. The carbon
dioxide (with some carbon monoxide) passes through the condenser and
then over a heated mixture of copper oxide and lead chromate contained
in a tube 15 cm. long. The gas (CO2) then passes through a U-tube,
in one limb of which is sulphuric acid, in the other glacial
phosphoric acid.
Pages:
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171