urbaf2

360 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

having a temperature of about 85°C is fed into a cast iron nitrator of 15 m^3 capacity

and cooled to 30°C.

The MNT which has already been used for the extraction of the spent acid from

dinitration and which contains some DNT, is introduced at first slowly and then

as HNO 3 is used up in the nitration to DNT, the flow rate is gradually increased.

The temperature in the nitrator rises to 60-65°C and then falls as the nitric acid is

consumed. When all the MNT has been run in, the temperature falls to 55°C. Then

the second stage begins. Nitric acid of a concentration of 60-70% of HNO 3 is

added. The rest of the MNT is nitrated to DNT, the temperature rising to 70-

72°C. The nitration is considered complete when MNT no longer steam-distils

from a sample taken from the nitrator.

The reaction mixture is allowed to remain at rest for one hour, then the acid

and DNT are separated. The composition of the spent acid is:

HNO 3 0.6%

NO 2 5-6%

H 2 SO 4 78-80%

H 2 O 13.4-16.4%

The spent acid is transferred to a cast iron dilutor-extractor, and the acid

containing DNT goes to a cast iron tank for temporary storage.

The spent acid in the dilutor-extractor is diluted with water to reclaim the great-

er part of the dissolved DNT. The following composition of the spent acid is

obtained on dilution :

HNO 3 0.5%

NO 2 4-5%

H 2 SO 4 73%

H 2 O 21.5-22.5%

The reclaimed DNT is added to the main yield of DNT, and the spent acid in

the extractor is stirred with MNT. Thus the rest of HNO 3 is used for nitration

to DNT, and at the same time the dissolved DNT is extracted. The MNT obtained,

containing dinitrotoluene, is used later for dinitration.

Spent acid from the extraction process has the following composition:

NO 2 44.5%

H 2 SO 4 73-74%

nitro compounds 0.2-0.3%

It is transferred to an intermediate storage tank, where it remains for 4-5 days.

During this time the rest of the MNT rises to the surface. It is collected and added

to the main portion, while the spent acid is conveyed to distillation.

Trinitration. This can be effected either by adding acid to dinitrotoluene or

by the reverse operation.