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482 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

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100 parts of phenol are added to 400 parts of sulphuric acid (sp. gr. 1.84) heated

to 110°C, then the whole is heated for 3 hr to bring it to a temperature of 130-140°C.

The solution is then cooled to room temperature and 1375 parts of nitric acid (sp.

gr. 1.20) are added gradually, the temperature being maintained at 45-50°C.

The mixture is left at room temperature for 24 hr, then heated gradually to about

90°C. After cooling, 2,4-dinitrophenol is filtered off, dinitrophenolsulphonic and

picric acids remaining in the filtrate.

Seyewetz’s method [38a]

Two modifications of this method are known. In one of them, applied at the

St. Fons Factory in France, between 1915-1918, sodium nitrate is used for the

nitration of phenol, and the other method utilizes dilute nitric acid.

Nitration with sodium nitrate is effected as follows. To a stoneware vessel,

sodium nitrate (195 kg), water (300 kg) and sulphuric acid of sp. gr. 1.84 (240 kg)

are added successively. The temperature rise brought about by mixing the sul-
phuric acid with water results in the complete dissolution of sodium nitrate. After

all the reactants have been introduced, the temperature of the solution is about
53°C. This is the temperature required for the initiation of the nitration reaction.
If the temperature is lower, it should be raised to 53°C by introducing live steam.
A solution of 25 kg of phenol in 40 kg of water heated to 26°C is poured in which
takes about 4 min. During this period the temperature should not be allowed to
exceed 80°C. If it does some cold water should be added. For the first 15-20 min
the reaction proceeds rather violently. It is accompanied by the evolution of large
quantities of nitrogen oxides.
After 60-75 min, when nitration has come to an end, water should be added
to bring the temperature down to 70°C and to reduce the solubility of dinitrophenol
in the spent acid.
The dinitrophenol rises to the surface of the liquid and may be skimmed off
by means of a small aluminium sieve. It is then washed in wooden vats and sepa-

rated on a vacuum filter.