Evening star., 1936-08-23

cSA AOdoAy dACStCu 0u1 AllS I1lC Paot oCb-
suit that New Orleans was selected
in response to an overwhelming de-
mand to go South"
SCIENTISTS now peer through sap
phire windows into the explosion
chambers of running automobiles, ac-
cording to a research report from
a gasoline corporation. Tests con-
Quoted in the laboratories in Detroit
by George Calingaert and S. d. Heron
and in the National Bureau of Stand
ards at Washington by Ralph Stair
show that synthetic white sapphire
is superior to quartz, the original ma
terial employed by Charles F. Ketter-
ing and his associates when they set
out to discover why engines knock.
The quest for new material was
undertaken because research workers
needed a clearer vision of what takes
place in the seething heat and terrific
pressures of cylinders of modern high
compression cars and airplanes. The
experiments, it is hoped by chemists,
will bring improvements in both fuels
and motors.
Natural white sapphires have been
cut occasionally as lenses for micro
scopes. Their hardness, high refrac-
tivity and weak dispersion made them
useful for that purpose. The cost of
even synthetic sapphire, however, has
prevented its development as a ma
terial for use in the automotive
laboratory. A quartz window was
used in research which led to the
discovery of a fluid as an anti-knock
agent.
Engineers point out, however, that
the very improvements which the
quartz window helped to bring about
have rendered it less valuable for
present-day investigations. The COM
bustion chamber of a modern auto
mobile develops heat of about $50
degrees Centigrade, while the pressure
rises to about 40 atmoSpheres. Quartz
is not mechanically strong enough to
stand up under such conditions. Be-
sides, it breaks down chemically dur
ing tests with loaded fuels and fails
to transmit infra-red rays for the
study Of chemical reactions inside the
combustion chamber.
The three Investigators tested quartz,
Spinel, sapphire. periclase and f1uorite.
Results indicate that sapphire is the
best all-around material. Spinel re-
sembles sapphire in its qualities. It
proved satisfactory in tests, except
that the samples used had a greenish
cast which interfered with the trans
mission of light. The researchers be-
lieve the green may have been due to
some impurity.
Periclase is even more transparent
than synthetic white sapphire, but it
is weaker mechanically. Further ex-
periments. however, may make 1t pos
sible to use both materials in investi-
cations to which they are especially
adapted.
While a general outline Of both
knock and anti-knock combustion has
been achieved. number of major
points are in doubt, according to au-
thorities. Certain products of knock
ing combustion are completely un-
identified Since these reactions can
not be studied outside the engine, it
is necessary to find better means of
seeing what goes on inside the engine
combustion chamber itself. The re-
cent development of a new high-speed
motion picture camera allows investi-
gators to take movies of the explosion.
Ever since the automotive engineer
has become aware of the importance, in
engine operation. of the chemical re-
actions which take place in the COM
bustion chamber, numerous devices
have been designed to permit observa-
ton of the inside of the combustion
chamber during operation of the en-
CINE" the report explains. mot salts
fled to measure temperature, pressure
and other factors, investigators have
used optical methods of observation,
either visual or involving measurement
and even the recording Of radiation in
tensity and wave length.