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316 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Another important feature in the nitration of dinitrotoluene is the coefficient

of distribution of nitric acid between the mineral and organic layers. The data for

sulphuric acid of 93% H 2 SO 4 at 90°C are given in Table 72.

TABLE 72

INFLUENCE OF CONCENTRATION OF HNO 3 IN THE NITRATING MIXTURE

ON THE RATE OF NITRATION OF DNT AND THE COEFFICIENT OF DISTRIBUTION

OF HNO 3 BETWEEN THE MINERAL AND ORGANIC LAYERS

Concentration (in %) 6.1 9.3 17.7 22.7 35.6 38.8 41.5

of HNO 3 in nitrating mixture

Yield of TNT (in mole/l.)

in homogeneous system 0.420 0.455 0.510 0.535 0.375 - -

in heterogeneous system 0.326 0.394 0.450 0.435 0.550 0.492 0.357

Coefficient of distribution

of HNO 3

% HNO 3 in mineral layer

1.24 1.20

% HNO 3 in organic layer

0.84 0.99 0.91 1.05

% HNO 3

o - homogeneous reaction

% TNT

∆ -heterogeneous reaction

FIG. 71. Influence of the content of

HNO 3 in nitrating mixtures on the

rate of nitration of DNT to TNT

(Orlova [2a]).

FIG. 72. Change of the rate of nitration

of DNT in the presence of TNT

(Orlova [2a]).

In both homogeneous and heterogeneous systems the rate of reaction increases
and then falls with increasing concentration of nitric acid (Fig. 71). In heterogeneous

systems the maximum corresponds to higher concentrations of HNO 3. The difference

can be explained in terms of coefficient of distribution. Hence the concentration
of HNO 3 in the mineral phase of the heterogeneous system reaches the value corres-