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506 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

If concentrated (98%) sulphuric acid has been used for the sulphonation, the

sulphophenol should be diluted with water prior to nitration, otherwise the nitration

reaction may proceed too violently. Besides some dilution is advantageous to pre-

cipitate any salts present, such as lead or ferric sulphates.

Lebedev [5] advises using wash water from the purification of picric acid, as

this effects some economy in nitrating and picric acids.

FIG. 112. Sulphonator for phenol (according to Lebedev [5]).

The dilution of sulphophenol is effected in special stoneware vessels. For 95 kg

of sulphophenol 72l. of wash water is added. The specific gravity of the sulphophenol

after dilution should be 1.35. The diluted sulphophenol is left to settle and then

filtered through a sand filter. The temperature of the sulphophenol which is to

be nitrated should not be lower than 50°C which is necessary for initiating the

nitration reaction.

Nitration of phenolsulphonic acid in movable vessels

The second stage in the manufacture of picric acid is the nitration of the phenol-

sulphonic acid (sulphophenol) obtained. The simplest reactors used for this process

are stoneware jars, “tourills”, which may be of various size (e.g. 85 cm diameter