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36 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

temperatures, according to the data given by several authors. The shapes of the

curves are the same for all measurements.

Bennett’s explanation of the existence of a maximum in the nitration rate at

the sulphuric acid concentration mentioned above is as follows. Since in nitration

FIG. 16. Variation of the rate of the nitration constant against the concentrations

of sulphuric acid in the nitrating mixture: I - Nitration of nitrobenzene at 25°C

(Westheimer and Kharasch [89]). II - Nitration of nitrobenzene at 25°C (Martinsen

[83]); III - Nitration of dinitromesitylene at 25°C (Westheimer and Kharasch [86]);

IV - Nitration of nitrobenzene at 0°C (Martinsen [83]); V - Nitration of anthra-

quinone at 25°C (Latter and Oda [32]); VI - Nitration of dinitrotoluene at 90°C

(Bennett [S]). He is Hammett acidity function defined by the equation

Reproduced from Gillespie and Millen [11].

with the nitronium ion a proton is split off from the nitrated substance (reaction 22,

p. 60) the presence of proton acceptors in the nitrating mixture should favour the ni-

tration reaction. Such a role is played for example by HSO 4 - ions, sulphuric acid,

which is able to form the H 3 SO 4 + cation with the proton, and HSO 7 - ions, that exist

in mixtures containing oleum.

Thus, the nitration rate would depend on two factors: on attaching the nitronium