TNT: Trinitrotoluenes and Mono and Dinitrotoluenes

THE MANUFACTURE OF TNT 33
is never accomplished. It is approached most nearly
with the three-stage process, in which process purification
is possible at each step. In order to compare
the three processes, an outline of each is given.
NOTE.—The acid mixtures given are approximate only. Each plant
has determined just which mixture will give the best results, some of
these mixtures varying as much as 10 per cent. A statement of the
exact analysis of the mixed acid is therefore impossible.
The One-stage Process. In the one-stage process,
but one acid mixture is used. This mixture consists
of 75 per cent sulphuric acid, and 25 per cent nitric
acid. The usual charge for this process is in the ratio
of one part toluene to twelve parts mixed acid. Each
kilogram of toluene requires, therefore, 3 kilograms
nitric acid and 9 kilograms sulphuric acid.
The toluene is added to the acid in the one-stage
process. The termination of the inlet pipe is in a kind
of well at the bottom of the nitrator, and the toluene is
nitrated before it can separate and spread about.
During the addition of the toluene the temperature
must not rise above 30° C. This addition requires
from two to two and one-half hours. After the addition
is complete, the temperature of the mixture is
raised to 90 to 95° C, by means of the steam coils.
This temperature is maintained for two hours, during
which time the mononitrotoluene is nitrated to dinitrotoluene.
The temperature is then further increased to
120°, and is " cooked " for an additional two hours.
The nitration is now considered finished, and the charge
is ready for separation, washing, and graining. In
many chemical plants a chemist tests the charge of
TNT, and the time of the final cooking is determined
by the solidification point of the mixed TNT and acid.