NITRO DERIVATIVES OF NAPHTHALENE 441The mixture is prepared from 600 kg of the spent acid from the dinitronaph-
thalene manufacture and 550 kg of the spent acid from mononitration, which
has been re-used for washing dinitronaphthalene. In consequence the spent acid
contains some of the HNO 3 adsorbed by dinitronaphthalene. The composition and
the quantity of the mixture should be so calculated as to contain 128 kg of HNO 3 ,
required for complete nitration of 300 kg of naphthalene.
FIG. 108. Diagram of a nitrator for the nitration of naphthalene
(Pascal [20a]).The naphthalene to be nitrated (300 kg) is added to the nitrating mixture during
aperiod of 3 hr. Meanwhile the temperature has risen spontaneously up to 50°C.
When all the naphthalene has been added, the nitrator contents are heated to 55°C.
After the completion of the nitration process, the mixture in the nitrator is allowed
to remain at rest to separate into two layers. Then the lower, acid layer is drawn
off into a lead lined tank (I) (Fig. log), 1.5 m high and 1.25 m in diameter. MoltenFIG. 109. Flow sheet of the nitration of naphthalene to nitronaphthalene
(Pascal [20a]).