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254 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

The lead block test is 330 cm^3 , and compared with picric acid (taken as 100),

it is 108-111.

The sensitiveness to impact is slightly lower than that of TNT. According to

Wohler and Wenzelberg [25], an impact energy of 12.1 kgm/cm

2

is necessary to

produce 50% explosion. Thus compared with picric acid (100) its relative sensi-

tiveness is 109, i.e. to bring about an explosion, the impact energy has to be higher

by 9% than that necessary to explode picric acid.

PREPARATION OF SYM-TRINITROBENZENE

Direct nitration of m- dinitrobenzene. Hepp [30] who first used this method

in 1887, reported that he was able to nitrate only two thirds of the dinitrobenzene

used, in spite of using anhydrous nitric acid and fuming sulphuric acid.

De Bruyn [16] in 1894 could not obtain a yield higher than 50%, by reacting

500 g anhydrous nitric acid and 1000 g of fuming sulphuric acid with 60 g of m- di-

nitrobenzene, in spite of carrying out the process for 5 days (1 day at 80-100°C

and the next 4 days at 110°C).

Trinitrobenzene has three good qualities as an explosive: high stability, great

explosive power, and a low sensitiveness to impact and friction. There were good

reasons for seeking more economic production methods. These investigations

were particularly intensive during World War I.

Radcliffe and Pollitt [45a] found that on nitrating m- dinitrobenzene with a

mixture of anhydrous nitric acid and 60% oleum at 110-120°C for 6½ hr, a 71%

yield could be obtained, and that by using 20% oleum a 56% yield was obtained.

According to Drumond [46], a yield amounting to only 29% theoretically can be

obtained as a result of nitration with a mixture of nitric acid and 20% oleum at

130°C for 3 hr.

The results of Hepp, Lobry de Bruyn and Desvergnes have been confirmed

by T. Urbanski and Simon [46a].

Moreover, Radcliffe and Pollitt found, that under certain conditions, the nitration

of m- dinitrobenzene yielded a product melting at 61°C which was not the 1,2,4-isomer

but, as they assumed, an “isomorphic modification of sym-trinitrobenzene”.

However, this view was shown to be wrong. Gibson [47] cast a certain doubt

on their statement and later T. Urbanski and Simon [46a] proved that the product

melting at 61°C formed in the nitration of m- dinitrobenzene is simply a mixture

of m- dinitrobenzene (35-50%) and sym-trinitrobenzene.

R. Robinson [67] reported that G. Müller nitrated m- dinitrobenzene to
sym-trinitrobenzene by using cold anhydrous mixtures of nitric and perchloric acids.

Preparation from α− α− trinitrotoluene. In 1893 a patent was granted to the Chemische
Fabrik Griesheim [47a] for the manufacture of sym-trinitrobenzene from trinitro-
toluene. The method was based on the fact observed by Tiemann [48] and by Claus

and Becker [49], that trinitrotoluene can be oxidized with nitric acid to trinitrobenzoic
acid, the latter being readily decarboxylated to form sym-trinitrobenzene: