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(^154) CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES
FIG. 26. Solubility of m- dinitrobenzene in sulphuric acid (Groggins et al. [1]).
Sometimes it is difficult to fulfill all the conditions a nitration mixture should
satisfy, such as a low solubility of the nitro compound at an adequate strength
of the acid. Sometimes water may be added, after the nitration has been completed,
to reduce the solubility of the nitro compound so as to obtain quantitative separa-
tion of the product. This can be justified economically although the acid becomes
diluted, thus necessitating the use of more oleum for fortifying the spent acid.
FIG 27. Influence of the concentration of nitrating mixtures on the nitration
of nitrobenzene to dinitrobenzene and phase conditions after cooling to 35°C
(Hetherington and Masson [9]).