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486 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

German method.

The German process of hydrolysis (applied at Griesheim) comprises the following

operations :

1300 kg of chlorodinitrobenzene and 7500 1. of water (90°C) are charged into

the reactor. To this mixture, 1500 kg of a 35% solution of NaOH is introduced with

stirring over a period of 4 hr, the temperature being maintained within 95-100°C.

If a test for a complete hydrolysis is satisfactory, the solution is introduced with

stirring to about 780 l. of hydrochloric acid (30%). The mixture is then cooled to

30°C and the separated dinitrophenol is filtered off on a vacuum filter, washed

with cold water, dried and ground.

Dry dinitrophenol prepared by hydrolysis of chlorodinitrobenzene usually melts

at 110-111°C. Its impurities come from the chlorodinitrobenzene, which may

contain unhydrolysed admixtures (such as m- chloronitrobenzene, dichlorodinitro-

benzene isomers, m- dinitrobenzene).

Dinitrophenol from chlorodinitrobenzene, to be used for the preparation of

picric acid, should satisfy the following specifications (Lebedev [39])

melting point (determined as setting point) not below 109°C

inorganic matter (ash) max. 0.2%

iron content in ash trace

lead content in ash none

dinitrophenates and picrates none

acid content (calculated on H 2 SO 4 ) no more than 0.1%

metal chlorides no more than 0.5%

chlorodinitrobenzene no more than 0.5%

dinitrophenol not less than 96%

PICRIC ACID

Picric acid is the most important of the trinitro derivatives of phenol. The com-

mercial product for military purposes is 2,4,6-trinitrophenol of high purity:

AS an explosive it is known under various names: Ekrasit (Austria), Mélinite

(France), Granatfiillung 1888-abbrev. Grf 88 (for shells), Sprengkörper 88 (for

field engineer cartridges) (Germany), Pertite (Italy), Shimoza (Japan), TNF
(Poland), Picrinit (Spain), Lyddit (United Kingdom), Melinit (U.S.S.R.).

PHYSICAL PROPERTIES

Picric acid crystallizes in colourless or yellowish needles or lamellae of the or-

thorhombic-bipyramidal system. The melting point of picric acid is 122.5°C and its