356 Determination of Carbon in Graphite. 
The connections from C to the aspirator are of gum elastic 
tube. D and Eare united above by a thin wire with a hook, 
for convenience of suspension in weighing them together, before 
and after the operation. In the tubulure of the retort, passing 
through a tight cork, is a slender glass tube X, doubly bent and 
descending nearly midway. It is drawn out to a long taper and 
hermetically sealed at the far end. Its chief use is to admita 
current of air during the aspiration, which forms the closing step 
of the experiment. But it is also useful as a means of introducing 
more sulphuric acid, should we find, late in the process, that 
enough has not been added to complete the oxydation of the 
graphite. This is done by removing the tip of the tube X with 
a file, and bringing a vessel containing sulphuric acid up around 
the open end. ‘The aspiration gently draws the liquid into the 
retort, and now the opening of the tube may be stgpped by a 
little ball of softened wax or cement. As however with the 
proportion of materials previously stated, such a recharging will 
scarcely ever be necessary, this appendage may be replaced by a 
vertical tube similarly sealed, to be opened only for the final as- 
piration. 
4. Mode of Manipulation.—On this head little need be added 
to what has been included in the preceding details. A brisk but 
not too violent evolution of CO, is to be maintained, by applying 
bubbles in their passage through the Liebig tube indicate by 
their persistent volume the completion of the oxydation. But as 
a further security we accelerate the evolution of oxygen by the 
lamp, and continue to maintain this stream of passing gas for 
several minutes. 
this way we have found that an amount of the divided graphite 
can be discerned, so small that, estimating it as carbonic acid in 
the absorption tubes, it would not affect sensibly a good balance. 
At the commencement of the experiment and before adding 
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