----“_~Nitro derivatives of mesitylene.....................
When all the acid has been added over a period of 4 hr, heat is applied to raise
the temperature to 90°C which is held for a further 2 hr. A test sample is steam
distilled and no smell of nitrotoluene should be present in the distillate.
If mononitrotoluene is detected, a further 50 kg of mixed acid is added and
heating is continued at 90°C for a further half an hour. The contents of the nitrator
are diluted with 350-400 1. of water to give a waste acid of 73% H 2 SO 4 contain-ing ca. 0.1% HNO 2.
After settling, the waste acid is run into the washing tank (a lead-lined vessel
of 12 m3
capacity) where the acid from three or four previous nitrations is collect-
cd and washed with sufficient crude nitrotoluene and o- nitrotoluene to form one
batch for nitration to dinitrotoluene. After settling, the washed waste acid is col-
lected in the acid storage tank. The nitrotoluene is pumped or blown to the nitrator.
In the washing tank, a stainless steel vessel of 12 m3
capacity, dinitrotoluene
is washed with 4000 1. hot water and the wash water is blown to drain. 4000 1. of
hot water are then run in and while stirring, sufficient solid NaOH is added to obtain
a neutral reaction. The wash liquor is discarded and the product is washed with
water to remove excess NaOH.
The molten dinitrotoluene is run into the vacuum dryer, and heated at 120°C
at a pressure of 15 mm Hg for 5 hr. It is tested for moisture by heating a small
amount in a test-tube and looked for condensation on the side of the tube. The
material is made up into solid blocks or flakes (flaking as for TNT, p. 379).
Dinitrotoluene, prepared by nitrating p- nitrotoluene, and free from m- nitro-
toluene, should not melt below 64.5°C. It should contain not less than 96% of
2,4-dinitrotoluene.
The specification, according to U.S.S.R. data (Gorst [2]) given below (Table
60) is for commercial dinitrotoluene, i.e. for the product prepared from a mixture
of nitrotoluenes.
TABLE 60
SPECIFICATION FOR COMMERCIAL DINITROTOLUENE
Appearance crystalline yellow product, free from
visible impurities
Moisture content below 1.5%
Mononitrotoluene con tent below 1.0%
Benzene insoluble substances below 0.1%
Ash below 0.1%
Sand in the ash not more than 0.05%
Acidity not more than 0.005% as H 2 SO 4
Melting point of the dry product not below 50°C and not higher than 55°C
Product used for nitration to TNT below 76°CIsomers of mononitro-m-xylene (MNX).....................
Pure 2,4-dinitrotoluene may be obtained by the direct nitration of p- nitro-
toluene. 2,6-Dinitrotoluene of high purity may be obtained from 2,6-dinitrotolui-
dine: