The Chemistry of Powder and Explosives - Sciencemadness Dot Org

272 NITRIC ESTERS
in both bulbs are at atmospheric pressure. The stopcock is closed, the
volume in the measuring bulb is read, thermometer and barometer are
noted, the volume which the air in the measuring bulb would occupy
at 20° and 760 mm. is calculated, and the mercury reservoir and the
bulbs are adjusted until the air in the measuring bulb occupies this
calculated volume and until the air in the compensating bulb is at
exactly the same pressure as that in the measuring bulb. A glass tube
Mercury
Compensating Measuring
\bulb / bulb
FIGURE 68. Du Pont Nitrometer.
Reaction
bulb
Mercury
reservoir
bent twice at right angles and containing some water is used for leveling
the mercury in the two bulbs. The position of the mercury in the
compensating bulb is now marked by means of a strip of paper glued
to the glass. Whenever in the future the gas in the compensating bulb is
again confined in this same volume, and whenever the nitric oxide in
the measuring bulb is confined at the same pressure as the gas in the
compensating bulb, then the nitric oxide will occupy the volume which
it would occupy if confined at 20° and 760 mm., and, if a 1-gram
sample was taken for the analysis, the reading will indicate correctly
the nitrogen content. If a sample larger or smaller than 1 gram was
taken, then the reading is to be corrected accordingly.