Evening star., 1939-07-29
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field. Laboratory
And Study
By Thomas r. Henri.

AND Stu0y
By Thomas r. Henry.
Evidence that heat causes big petro-
leum molecules to explode into frag-
!! ments has been reported to the Ameri-
can Chemical Society by Drs. F. o. Rice
and K. F. Herzfeld Of the Catholic Uni
versity of America.
The large molecules, their experiments
indicate, blow up into radicals" as the
fragments are called, instead Of breaking
into two smaller molecules. This has
an immediate application to the
cracking of petroleum. While chem
lists have known for years that by heat
ing the gaseous portion of petroleum
under very high pressures part of 1t
can be made to condense to form liquids,
the molecular processes involved have
not, up to the present, been understood.
According to the free radical theory"
Of the Catholic University professors, it
is held that these radicals, once they
have been formed by the molecular ex-
plosions, have the power to attack other
molecules and to cause these, in turn,
to blow up and generate new radicals,
which continue the process.
Depending on conditions, they report
ed, such chain reactions can be dan
gerously explosive or can be controlled
so that it is possible to conduct them in
chemical plant.
Until few years ago the free radical
theory was not given serious considera-
ton by the majority of chemists, who
preferred the theory that heat caused
big molecule to break directly into two
smaller ones. Free radicals were re-
garded as mythical entities, invented
without any real excuse.
In making theoretical study Of the
problems, the two professors said, they
have calculated the number OF free radi-
Gals present under certain conditions and
have shown that their destructive effect
is so great that there is no need to
assume any other type of reaction.
From a practical standpoint" Profs.
Rice and Herzfeld report, "the aim is to
find conditions of temperature, pressure,
contact time and catalyst that will pro-
duce various desired products from ma
terials found naturally. If a chemical
process can be brought about by the
application Of heat relatively simple and
inexpensive equipment Is sufficient. One
OF the Oldest large scale chemical indus
tries, the manufacture of city gas, is,
or used to be, carried out simply by
heating coal in an iron retort Besides
Illuminating gas, many other products
were obtained from this process, which
still is extensively used in the prepara-
ton OF coke in connection with the steel
industry.
petroleum is an exceedingly compli-
Gated mixture of hydrocarbons, and only
a small proportion is suitable for use
as fuel in the present-day automobile
engine. The problem is to find some
use on the one hand for the thick, heavy
part of the oil, and on the other hand
for the gaseous part, neither of which
Is suitable as ordinary gasoline
There are two methods of attack, by
engineering and by chemistry. The en-
gineering method would be to build
automobile engines that could use the
thick. heavy oil. The present automo-
bile engines could use the gaseous part
OF petroleum if the gas tanks were re-
placed by tanks in which the petroleum
gasses could be stored under pressure.
The chemical method is to convert
the heavy oil and gases by chemical
means. great deal of progress has
been made along these lines and a great
deal OF empirical knowledge has accu-
mulated. Chemical research work has
been carried on very actively for many
years, much of it spurred on by curl
osity as to how the reactions occur"
A molecule under ordinary conditions
suffers about billion collisions a Sec
ond, 1t was reported by DR.. Eugene P.
Wigner of Princeton University at the
same symposium
IN spite OF this great number of COL
lisions, he explained, all chemical reac-
tions are not instantaneous, because
every encounter leads to a chemical
change. The two molecules can partici-
pate In chemical reaction only If they
collide.
since direct measures of rates of reac-
ton are difficult, Prof. Wigner said, a
theory OF reaction rates has been formu-
lated enabling chemists to predict and
classify them according to the readiness
OF molecules to unite There are two
different types of reactions, depending
on the magnitude of the energy of the
molecules.
In reactions of the first type only a
very few molecules with energies greater
than certain limit can take part. The
energy content of each molecule f1uctu-
ates around comparatively low value
and only rarely reaches the amount
which permits a fruitful collision. In
reactions Of the second type the collid-
ing molecules have too much energy
This disrupts the newly formed com
pound unless 1t is carried away by a
third body.