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334 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Muraour observed the important fact that trinitro-m-xylene reacts with sodium

sulphite only with great difficulty, while trinitromesitylene does not react with

it at all. Tetranitromethane, which is a common impurity of TNT, reacts with

sodium sulphite to yield a water-soluble salt of sulphonic acid (p. 339).

After sulphitation, the setting point of TNT rises on the average by 2.2°C

(e.g. from 78.0°C to 80.2°C).

Barbiere [145] examined quantitatively the process of sulphitation of α−, β−

and γ− trinitrotoluenes using a 6% solution of Na 2 SO 3 at different temperatures

(30-60°C) and in another series of experiments the influence of the concentration

of sodium sulphite solution on the solubility of the isomeric trinitrotoluenes at 30°C.

He also determined:

(a) the total solubility of α− trinitrotoluene (S 1 ) which includes both the formation

of the soluble addition compound and sodium salts of nitrosulphonic acids;

(b) the “irreversible” or “real” or permanent solubility (S 2 ) which is caused

only by formation of sodium salts of nitrosulphonic acids.

FIG. 75. Influence of the concentration of sodium sulphite solution

on solubility of α−, , β− and γ− trinitrotoluene (Barbiére [146a]).

This was determined by diluting the solution to hydrolyse the addition com-

pounds. Precipitation of recovered α− trinitrotoluene gives the “transient” solubility
(S 3 ). By definition S 2 = S 1 -S 3.

Some of Barbiére’s results are given in Fig. 75. Here both the total and real

solubility of α− trinitrotoluene are shown.

D. Smolenski and Plucinski [146] made a thorough study of the sulphitation
of α−, β− and γ− trinitrotoluenes. Some of their results are summarized diagrammati-
cally in Fig. 76 which illustrates the influence of sulphitation temperature on total,