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338 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

sym-trinitrobenzene results (p. 254). According to Schmidt [147], 2,4,5-trinitro-

benzoic acids gives rise to hydrolytic denitration to yield 2,4-dinitro-5-hydroxy-

benzoic acid (I).

(31)

It is probable that 2,4-dinitro-3-hydroxybenzoic acid (II) can also be formed in the

similar way :

(32)

II

Also hydroxy-2,4,6-trinitrobenzoic acid (III) can be present among the other

by-products in the formation of trinitrotoluene.

Hydroxynitro acids (I), (II) and (III) are (according to Schmidt) washed from

the crude TNT and are present in the wash-waters. Trinitrobenzoic acids remain

in TNT as impurities. The trinitrobenzoic acids formed are readily decarboxylated.

CO 2 is evolved and only trinitrobenzenes remain in TNT as its impurities.

As a consequence of the strong oxidation processes occurring mostly during the

trinitration (naturally at the expense of nitric acid) a relatively large quantity of

nitrous acid is formed, which in sulphuric acid medium gives nitrosyl sulphuric

acid :

According to Kobe and Lakemeyer [17], the nitrosylsulphuric acid represents

about 17 wt. % of the total amount of spent acid from the trinitration. Its presence

would subsequently considerably affect the process of the nitration of toluene to

the mononitro-product, since it makes 14-17 wt. % of the acid used for the mono-
nitration.
According to Gorst [2], the rate of the oxidation reactions falls with increase
in the value Φ, or in other words with the increase of concentration of H 2 SO 4 in
the nitrating mixture or in the spent acid. A diagram (Fig. 102) related to nitration
of dinitroxylene is given on the (p. 396).