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TNT MANUFACTURE 391

The water may be decolourized by chlorination, but this requires large quan-

tities of chlorine. Biological processes can lead to destruction of TNT, but the

sulphonic acids remain unaffected.

For this reason, according to Kratz, the most rational way of removing TNT

and salts of nitrosulphonic acids from the water is by simply distilling off the water

and then destroying the non-volatile residue.

Since this method is expensive as regards capital and operating costs, Kratz

has suggested a method of treatment for acid waste water from the TNT manu-

facture consisting in agitating with 5-10% milk lime.

The reaction with calcium hydroxide is rather slow, so agitation should go on

for some time (5-15 min). The mixture is then allowed to remain at rest for clari-

fication. Treatment with milk of lime neutralized the acids and caused the precip-

itation of several coloured compounds, among others the products of the reaction

of trinitrotoluene with calcium hydroxide. The amount of calcium oxide consumed

in the process is 700 tons monthly, at an output of 4000 tons of TNT a month.

SAFETY IN TNT MANUFACTURE

The manufacture of TNT is one of the safest operations in the explosive industry.

Nevertheless, any negligence about safety regulations may have disastrous conse-

quences. Because the manufacturing process is regarded as safe, the fact must

not be overlooked that less experienced personnel may disregard the regula-

tions.

The most hazardous operation in TNT manufacture is nitration, primarily

mono- and tri-nitration. In mononitration the hazard is due to the extremely violent

reaction of the unreacted hydrocarbon with the nitrating mixture, and to the fact

that nitro derivatives of cresols are formed in the process, along with nitrotoluenes.

The last stage - trinitration - is dangerous due to the drastic conditions of the

reaction which requires concentrated acids and a high temperature. The earlier

method of trinitration at which temperatures up to 120°C were applied, was partic-

ularly hazardous. If the mononitrotoluene has not been freed from nitrocresols,

trinitration is still more dangerous, due to the high reactivity of nitrocresols, and
their liability to undergo oxidation. The formation of carbon monoxide may

also be a cause of an explosion in the course of trinitration [33] (p. 339).

The spent acid from trinitration has also been the cause of several disasters,

although it had been considered safe to handle. The most noteworthy example

of this occurred in the Reinsdorf factory in Germany in 1935. The hot spent acid

flowed down to open iron tanks, where, as the liquid cooled, a mixture of di- and

Tri-nitrotoluenes rose to the surface. It was skimmed off from time to time and

transferred to a washing tank, where it was washed with water. On skimming,

a rubber glove and a shelf left on the brim of the tank with some cotton wool on it,
fell into the tank. The reaction between the spent acid and the rubber and cotton wool

initiated violent decomposition and fire. An attempt to extinguish the flames failed,