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348 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Old French process.

This process, as described by Pascal [5], was used in France both during World

War I and in the early period of time between the two wars. Separate operations

in the three-stage nitration process are carried out in the following way:

Nitration of toluene to MNT (“mononitration”). To introduce one nitro group

into toluene a mixture of acids is used (sp. gr. 1.672) of composition:

HNO 3 28%

H 2 SO 4 56%

H 2 O 16%

Toluene (650 kg) is run into a nitrator, and 1580 kg of the nitrating mixture

is added with vigorous stirring. The temperature in the nitrator should be main-

tained at 40°C by using a cooling jacket and a coil situated inside the nitrator.

After the reagents have been mixed thoroughly the temperature of the mixture

should be raised to 60°C and maintained then for 45 min to 1 hr. When the reaction

has been completed the nitrator contents are cooled to room temperature and the

stirrer is stopped. The liquid is allowed to stand still until quiet, and then the lower

layer, i.e. the spent acid, is drained off.

The composition of the spent acid (sp. gr. 1.66) is:

HNO 3 trace

H 2 SO 4 69%

H 2 O 29%

NO 2 2%

From 650 kg of toluene 910-950 kg of MNT is obtained, i.e. 140-146 kg for

100 kg of toluene. Since the theoretical yield is 149 kg of MNT for 100 kg of toluene,

the actual yield amounts of 94-98% of theory. Losses are due mainly to dissolution

of the nitration product in the spent acid (up to 4.5% of the total amount of nitro-

toluene).

Nitration of MNT to DNT (“dinitration”). The acid from the first stage of

nitration, composed of:
HNO 3 32%
H 2 SO 4 61%
H 2 O 7%

is run into MNT over a period of 2 hr, with constant stirring. The amount of the

acid should correspond to a 45% excess of HNO 3. During stirring the tempera-

ture should be maintained at 40°C for the first hour and at 50°C for the next hour.

When all the acid has been run into the nitrator the mixture is heated to 90°C

and maintained at this temperature for half an hour. Then the nitrator contents

are cooled to 60-65°C, i.e. to a temperature at which crude DNT remains liquid
(m. p. 56-58°C).

Spent acid from dinitration has the composition:

HNO 3 2.5%

H 2 SO 4 76.0%

H 2 O 20.0%

NO 2 1.5%