Hydrolysis of chlorodinitrobenzene

In industrial practice, hydrolysis of chlorodinitrobenzene is now the main method of producing dinitrophenol. The reaction proceeds as follows ... 

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). 

Picric acid is produced either by nitrating phenol or by nitrating dinitrophenol prepared by hydrolysis of chlorodinitrobenzene. 

Towards the end of this operation a sample should be taken and diluted with water to test whether hydrolysis is complete. A completely hydrolysed product will go into solution. Otherwise chlorodinitrobenzene will collect as an oil. 

---