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306 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

position. The lead content varies from 23.5 to 64.5% Pb, depending on the mode

of their preparation.

On reacting TNT with metals in the presence of mixtures of nitric and sulphuric

acids diluted with water similar products were obtained, although the presence of

sulphuric acid inhibited their formation to some extent. These products can be

formed in production while TNT is being washed free of acid by water, for when

most of the sulphuric acid has been removed, the remaining nitric acid is strongly

absorbed by molten TNT.

According to the Kovache and Thibon, these metal compounds may be formed

in several lead or iron parts of the plant and are a potential cause of ac-

cidents.

Kovache and Thibon also found that similar inflammable metal products were

formed by lower nitrated toluene derivatives, e.g. p- nitrotoluene and 2,4-dinitroto-

luene, and also by trinitrobenzene. Nitrobenzene and trinitroxylene did not react

in this way.

It seems certain that the products discussed have fairly complex structures,

being the result of a partial reduction of a nitro group (or groups) by the metal in

an acid medium, followed by oxidation by nitric acid. The oxidation leads to ill-defined

inflammable products of high molecular weight.

Effect of heat

Trinitrotoluene is very resistant to heat. Extensive investigations of this prop-

erty of TNT have been carried out by Kast [54] and Verola [68], both of whom

obtained consistent results.

According to Verola, heating TNT at 130°C for 100 hr does not bring about

any decomposition. Kast, when heating trinitrotoluene at 150°C for 4 hr, found

no gases evolved from its decomposition. According to Verola, a distinct evolution

of gaseous decomposition products starts at 160°C.

Kast established that at a temperature of 240°C, trinitrotoluene ignites in 0.5 hr.

At 270°C marked exothermic decomposition takes place. Temperatures from

295-330°C are the true ignition temperatures of TNT (Verola found 281-286°C).

According to Micewicz and Majkowski [95], the ignition temperature of TNT

is 312-318°C.

Verola has also examined the effect of prolonged heating on the melting point

of TNT. Heating at 145-150°C gave the following results:

m. p.,°C

Before the experiment 80.75

After 18 hr heating 80.66

After 42 ,, ,, 80.55

After 80 ,, ,, 80.25

After 127 ,, ,, 80.20

After 158 ,, ,, 80.13

After 177 ,, ,, 79.90