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408 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

loses about 12% in weight. The oily product separated along with water is allowed

to settle in special tanks and should then be utilized for special purposes. After

centrifugation, the trinitroxylene still contains 15-18% of water. As Kravchinskii

believed, the melting point of the product could be raised from 168°C to 176°C

as a result of centrifugation.

FIG. 103. Wooden vat for washing TNX: 1 - wooden lead lined walls, 2 - rubber

sleeve to introduce TNX, 3 - lead bubbler (Kravchinskii [3]).

Two-stage preparation of TNX

The two-stage preparation of TNX consists in the nitration of m- xylene in two

stages.

This method has been applied in the U.S.S.R, two modes being used:

Xylene -> DNX -> TNX

or Xylene -> MNX -> TNX

Nitration via DNX. In the first stage of the process - dinitration of xylene-

the following nitrating mixture is used:

HNO 3 20%

H 2 SO 4 65%

H 2 O 15%

The mixture is run into the nitrator, and when it has attained a temperature

of 25°C, feeding with xylene starts until the acid to xylene ratio is 6.5, which corre-

sponds to an excess of HNO 3 amounting to 10% of theoretical. While adding