The Chemistry of Powder and Explosives - Sciencemadness Dot Org

UTILIZATION OF COAL TAR 129
the nucleus. The nitroanilines are more difficult to nitrate than
aniline because of their inhibiting nitro group, and more easy to
nitrate than nitrobenzene because of their promoting amino group.
In o- and p-nitroaniline the amino and nitro groups agree in
activating the same positions, and both substances yield 2,4,6trinitroaniline
when they arc nitrated. In m-nitroaniline, the
nitro group "activates" the 5-position, while the amino group
activates the 2-, 4-, and 6-positions. Nitration takes place under
the influence of the ortho-para -orienting amino group, and 2,3,4,6tetranitroaniline
results.
Utilization of Coal Tar
The principal source of aromatic compounds is coal tar, produced
as a by-product in the manufacture of coke. Gas tar, of
which much smaller quantities are produced, also contains these
same materials. Aromatic hydrocarbons occur in nature in Borneo
and other petroleums, and they may be prepared artificially by
stripping hydrogen atoms from the cycloparaffins which occur in
Caucasus petroleum and elsewhere. They are also produced from
paraffin hydrocarbons by certain processes of cracking, and it is
to be expected that in the future aromatic compounds will be
produced in increasing quantity from petroleum which docs not
contain them in its natural state.
Coal yields about 6 per cent of its weight of tar. One ton of tar
on distillation gives:
Light Oil—yielding about 32 lb. of benzene, 5 lb. of toluene, and 0.6
lb. of xylene.
Middle Oil—yielding nbout 40 lb. of uhenol and cresdls, and 80-120
lb. of naphthalene.
Heavy Oil—yielding impure cresols and other nhenolti.
Green Oil—yielding 10-40 lb. of anthracene.
Pitch—1000-1200 lb.
Naphthalene is the most abundant pure hydrocarbon obtained
from coal tar. It takes on three nitro groups readily, and four
under vigorous conditions', but ordinarily yields no product which
is suitable by itself for use as an explosive. Nitrated naphthalenes,
however, have been used in smokeless powder and, when mixed
with ammonium nitrate and other materials, in high explosive*
for shells and for blasting.
The phenol-crcsol fraction of coal tar yields phenol on distillation,
which is convertible to picric acid, and the cresols, of which