NITRO DERIVATIVES OF TOLUENE^307In another set of experiments Verola obtained:
m.p.°C
After heating for nearly 290 min at 180°C 78
After heating for nearly 180 min at 201°C 17
After heating for nearly 45 min at 217.5°C 59TNT is difficult to ignite. When heated directly in a flame it melts, and ignites
only when brought to a high temperature (about 300°C). For this reason the viewhas been accepted that TNT is safe to handle at high temperatures and in the presence
of a flame.
However, the fact should be taken into account that molten TNT is more sensi-
tive to impact than in the crystalline state (p. 320, Table 75, Fig. 74). Moreover,
if large quantities of TNT ignite, combustion might proceed very vigorously, and
even cause detonation.
Experiments carried out after the accident described on p. 393 have shown that
a lighted cigarette, thrown onto a sack containing about 50 kg of TNT, is able to
cause the TNT to detonate.
Effect of light
It has long been known that trinitrotoluene undergoes far-reaching changes
under the influence of sunlight. Dark coloured products are formed, the structure of
which is not yet fully understood.
In 1907 Kast [57] found that the melting point of trinitrotoluene fell from 80.0°C
to 795°C after irradiation for a fortnight.
Molinari and Giua’s investigations [96] showed that the melting point of trini-
trotoluene which has been exposed to sunlight for 3 months in the open fell from
80°C to 74°C. When, however, trinitrotoluene was irradiated in absence of air
in vacuum, hardly any changes in colour and melting point were observed.
According to Oddo [97] and Lodati [98], under the influence of radiation trini-trotoluene partly loses nitrogen and is transformed into a compound of acidic
character.
Schultz and Ganguly [99] suggest that trinitrotoluene undergoes a number of
isomerization processes, consisting in transferring the oxygen of a nitro group to
the methyl group (as in Ciamician and Silber’s reaction). The nitro compound
XIII reacts like quinone oxide (XIVa and XIVb):