2,4,6-Trinitrobenzoic acid has been prepared by heating trinitrotoluene
with fuming acid in a sealed tube to 100'0, for two weeks,[1a]
the oxidation being only partial. It can also be prepared by heating
trinitrotoluene under a reflux condenser, with a mixture of 5 parts
of concentrated nitric acid and 10 parts of concentrated sulfuric
acid;[1] this method is, however, unsuitable in the laboratory
owing to the difficulty of devising suitable apparatus.
Another method is to dissolve trinitrotoluene in nitric acid and,
to this solution (at 95'0), to add potassium chlorate at such a rate
that the temperature does not fall;[2] this method has been found
to be difficult to control on a laboratory scale.
[1a] Ber. 3, 223 (1870)
[1] D. R. P. 77,559; Frdl. 4, 34 (1894)
[2] D. R. P. 226,225; Frdl. 10, 167 (1910).
The method described above is a modification of a patented process,[3]
in which trinitrotoluene suspended in sulfuric acid is treated
with chromic anhydride.
[3] D. R. P. 127,325; Frdl. 6, 148 (1901).