The Elbert County tribune., 1908-06-11
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ly machines where the lighting gas
Is cleansed from its impurities, and
the different by-products are separated
from each other. First are great
''condensers,' in which the gases are
cooled. The cooling condenses the
heavier compounds into thick liquids
which are then left behind.
One of the substances later re-
moved from the gas is ammonia, and
from this product is made the am
monia water which is used in every
household.
The heavy. strong smelling, black
| liquid which is collected in the cooling
of the gas Is what we know as coal
tar. This is an exceedingly complex
mixture of substances. From it are
obtained not only creosote OIL but
most of the dyes which are used nova
days, perfumes, and even favoring
extracts.
Gas. coal tar and coke are also made
in what is known as the byproduct
coke oven, which is adapted to differ
ent objects, but is operated on the
same principle. Its coal tar is equally
as good as the gas works tar for max
| in3 creosote oil. In recent years a
great amount OF gas has been made in
the United States by another process,
and is known as water gas. This proc
ess also produces tar. which looks
much like coal tar and is often difficult
to tell from 1t. But this tar is really
derived from petroleum, and does not
make good oil for preserving wood
from decay. Wood creosote, with
which SO many people are familiar, is
likewise obtained from wood tar
which is produced by distilling wood.
But like water gas tar creosote, wood
| creosote is not so good for wood
| preservation as is the coal tar creo-
sote. When creosote is bought for that
purpose, therefore. it should be GER
tain that it is coal tar creosote.
To obtain creosote oil from coal tar
the tar is, in its turn distilled. But
this distillation is like that used for
other liquids instead of that employed
for the coal. The still is heated. and
as the heat increases the light oils
first pass over. Among these is the
familiar carbolic acid. This is a pow
erful antiseptic, but it is not desirable
in wood preservative, for 1t evapo-
rates SO readily that it soon becomes
lost from the wood. When a tempera-
ture of about 400 degrees has been
reached, the distillate is turned into
! another receiver, and from this point
on to 500 or 700 degrees creosote
oil is produced One of the substances
which is contained in this mixture is
"napthalene.' from which common
moth balls are made. Coal tar creo-
sote. thus produced, is the great wood
preservatiye.
The residue remaining in the still
after the distillation is pitch" which
is chiefly used together with coal tar
saturated felt in the preparation of
gravel or Stag roofing. In America
roofing pitch is the chief end for which
ta- is distilled. In Europe this is
not so true. Now pitch for roofing
must be rather soft Therefore tar
distillation is not carried so far in this
country as 1t is in Europe. For creo-
sote oil it would be better if it were
carried farther, since the substances
which distill at the higher tempera.
lures in most cases neither evaporate
in the air nor dissolve in water as
readily as those which distill more
easily. Consequently they stay in the
wood for longer time, and protect IT
correspondingly from decay.
Much study is being devoted by the
United States forest service to creo
sote oil, to determine what its compo
sition should be to give the best re
suits In preserving timber, under diff
ferent conditions, and how the most
desirable creosotes may be obtained
The reports of these studies. together
with detailed description of the more
economical processes of applying the
preservatives to wood, have beer
worked into circulars which the gov
ernment has placed at the disposal Of
all users Of timber and which will be
furnished to all who make the request
Of the forester at Washington.