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710 Proceedings of the Boyal Society of Edinburgh. [Sess. 
emptied into the combustion tube. The absorption tubes and oxygen 
supply are next attached and the combustion begun. The two burners at 
the front (absorption end) of the tube are lit and tiles are placed over them, 
the heat being as far as possible confined to the portion of the tube covered 
by the tiles by means of screens of asbestos paper. When the copper oxide 
has attained dull redness, the third Bunsen is lit at the other extremity of 
the tube without a tile. The heat from this Bunsen gradually volatilises 
the substance, with or without decomposition, the volatile products being 
for the most part burned in the moderately rapid stream of oxygen (2-3 
bubbles per second) which is all the time passing through the apparatus. 
The Bunsen is gradually moved forward as the combustion proceeds, tiles 
being placed behind it to keep the tube still hot. Under ordinary con- 
ditions there is no visible reduction of copper oxide to metallic copper, 
although towards the end of the combustion the oxide usually glows 
immediately behind the tiles at the absorption end of the tube. To burn 
any carbon that may be left on the tube by decomposition, all the tiles are 
placed in position, and the three burners adjusted so that the tube is 
heated as uniformly as possible to dull redness. The carbon at this 
temperature is not graphitised and burns off readily. When the oxygen 
comes freely through the indicator bottle at the end of the apparatus, the 
combustion is finished, and very little sweeping out is necessary, owing 
to the small volume of the apparatus. Immediately after the combustion, 
the copper oxide is returned to the tube A, and is ready for the next 
analysis. 
The time occupied between attaching and removing the absorption tubes 
need not exceed half an hour. The amount of oxygen consumed in a 
combustion averages 800 c.c. 
In order that an idea may be formed of the rapidity and accuracy of 
the method, the following results may be quoted. Four combustions of 
succinic acid were performed, including weighing, between 9 a.m. and 1 p.m., 
two sets of absorption tubes being used, in order that no time might be lost 
in waiting for the tubes to cool before weighing. 
Quantity taken. 
Percentage Carbon. 
Percentage Hydrogen. 
0T866 g. 
40-61 
5-28 
0T492 g. 
40-44 
5-20 
0T890 g. 
40-48 
5-18 
0-1733 g. 
40-56 
5-20 
The theoretical percentages for C 4 H 6 0 4 are, carbon =40'68, hydrogen = 5 -09. 
