534 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVESto detonate is lower. Thus, when compressed to a density of 1.63 it requires a
powerful detonator (at least 2 g of mercury fulminate). Picric acid of the same density
can be detonated by 0.6 g of the same detonator.
The following figures characterizing the explosive properties of trinitro-m-
cresol were given by Kast [7]:
heat of explosion 925 kcal/kg
volume of gases, V 0 675 I./kg
temperature of explosion 2700°C
maximum rate of detonation 6850 m/sec
specific pressure, f 7595 m
expansion in the lead block 275 cm^3 (i.e. 90% of that given by picric acid)The heat of the formation (−∆ Hf) of trinitro-m-cresol is +54.1 kcal/mole,
according to Koehler [25].MANUFACTURE OF TRINITRO-m-CRESOLIn industrial practice, trinitro-m-cresol is prepared by the nitration of cresol.
The manufacturing process is similar to that used for picric acid. It consists of two
stages - sulphonation and nitration. However, due to the liability to oxidation,
its yield does not exceed 150-160 parts from 100 parts of pure m- cresol, i.e. a maxi-
mum of 67-73% of the theoretical yield.
From 100 parts of commercial “meta-cresol” containing only 60% of the m- iso-
mer (the rest being p- cresol) not more than 100 parts of trinitro-m-cresol can be
obtained. p- Cresol is fully oxidized to oxalic acid, which then crystallizes from the
spent acid.
The isolation of pure m- cresol has proved to be too expensive because the
boiling points of the m- and p -isomers are too close to each other:
boiling point, °C melting point, °C
m- cresol 201 11-12
p- cresol 202 36
o- cresol 185 31
Experiments have been carried out to separate m- and p- cresols by sulphonation,
as sulphonated m- cresol is a liquid substance, while sulphonated p- cresol is crys-
talline. The two isomers were then separated by centrifugation. However, the purity
of the product obtained was not satisfactory enough, thus the process would not
be economical.
In the absence of any other criteria, a sample of each “meta-cresol” batch to
be nitrated should be subjected to a laboratory nitration test.
The process of cresol nitration is much the same as that for phenol. In France,
where the output of Cresilite was highest, movable stoneware jar-nitrators (“tourills”),
or the stationary type described above were used for the nitration (pp. 506, 509).
Nitration of m- cresol in stationary nitrators was carried out as follows:
1860 kg of 52% nitric acid is charged into the nitrator, followed at a fairly highrate by sulphocresol (obtained by sulphonation of 200 kg of commercial “meta-cre-
sol” with 600 kg of sulphuric acid, sp. gr. 1.84, as described above in the picric acid