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NITRO DERIVATIVES OF TOLUENE 291

Jefremov and Khaibashev [60] have also investigated melts of TNT with other

nitro compounds. They observed deep minima on the isotherms of plastic flow

of mixtures of TNT and picric acid, trinitroxylene or 1,8-dinitronaphthalene.

corresponding to eutectic mixtures. Unlike those the corresponding curves for
mixtures of TNT and 2,4-dinitrotoluene, m- dinitrobenzene, and tetryl, showed

an additive character.

Crystallization. Very often it is necessary to obtain explosives (TNT among

them) in readily precipitated form. Cave, Krotinger and McCaleb [61] developed

a general method of crystallization which consists essentially in introducing the

hot solution of a substance into cold diluting liquid or solid carbon dioxide.
Thus when a solution of α− trinitrotoluene in methanol is introduced into water,
small and uniform crystals which are readily “pourable” are formed. Less uni-

form crystals of needle like form are obtained by pouring a methanol solution of

α− trinitrotoluene into solid carbon dioxide. The results are given in Table 67.

TABLE 67

Methanol Average dimen- Limits of

solution of TNT sions of the dimensions

Ratio of axes

is poured into crystals, μ of the crystals, μ

length/width

solid CO 2 29 3.5430 9.6

water 25 6-60 3.0

The rate of crystallization of TNT has been studied by Pelchowicz and Berg-

mann [62]. They found it decreased when various compounds were added, forming

homogeneous melts with TNT, for example certain aromatic compounds, among

others picric acid.

The elucidation of the influence of admixtures on the linear rate of crystalliza-

tion of TNT has been the subject of more detailed studies by Gey, Dalbey and

Van Dolah [63]. They found that some compounds, as for example 2,4,6-trini-

trostilbene and a number of its derivatives (e.g. 3-nitro-, 4-nitro-2-chloro-, 2-meth-

oxy-, 4-hydroxy-, 4-methoxy-), caused a very sharp fall of the rate of crystalli-

zation of TNT. For example, the addition of 1 mole % of 2,4,6-trinitrostilbene

to TNT reduced its linear rate of crystallization at 74°C almost nine times: from

2.5 cm/min (pure TNT) to 0.29 cm/min.

Other compounds such as 2,4-dinitrotoluene, 2,4,6-trinitro-m-xylene, 2,4,5-

trinitrotoluene, hexogen, only slightly decreased the rate of crystallization (e.g.

the addition of 1 mole % of 2,4-dinitrotoluene and hexogen caused a decrease in

rate of crystallization of TNT at 74°C from 2.5 cm/min to 1.89 and 1.78 cm/min

respectively).

Boiling point and vapour pressures. Giua [64] reported in 1919 that trini-
trotoluene may be boiled. According to this author, it can be distilled off at 210-

212°C, under a reduced pressure of 10-12 mm Hg without any visible decompo-
sition.