Evening star., 1923-08-12

Prof. Kamerlingh Onnes at Leyden.
There are some practical difficulties
In the production of the liquid. how
ever, which have prevented a larger
number OF laboratories from in
stalling the necessary equipment.
The purpose of the bureau of stand
/ ards has been, first, TO be able TO pro-
duce the liquid for use in the produc-
tion OF extreme low temperatures for
scientific Investigations: and second
to study the difficulties of the method
| with the purpose of rendering its use
| by other laboratories easier
The principle of the method EN-
| ployed is comparatively simple. The
hydrogen is first compressed TO
pressure of about 70 TO 100 atmos
pheres, then preceded TO tempera-
ture of about 200 degrees centigrade.
which is produced by the forced evap-
grafton of liquid air under reduced
pressure and then passed through a
heat exchanger. consisting Of close
coil of copper tubing and allowed I"
expand to atmospheric pressure
| through a valve. The gas is further
cooled by the expansion and the cold
gas is used to cool the incoming gas
I by passing it around the heat ex-
changer of copper tubing. This proc
ess reduces the temperature until
part Of the hydrogen liquefies.
|
GST~HE principal difficulty en-
J. countered results from the pres
ence of impurity in the hydrogen.
Since the temperature of liquid hydro
gen is well below the freezing point
of air. any air present in the hydrogen
is frozen out in the liquefier, and since
| IL tends TO collect at the expansion
valve, the valve very quickly be-
comes plugged unless the hydrogen Is
extremely pure. This may occur even
when the gas is so nearly pure that
an ordinary gas analysis indicates
| 100 per cent hydrogen.
| "The work at the bureau has been
greatly facilitated by the develop
ment OF a method for determining
nitrogen in hydrogen, which Is more
sensitive than the usual method This
has made it possible to follow, by
analysis. the composition OF the gas
at various steps In the production and
use, and determine when and how
impurity enters.
| Inc uToBcl ID SCHCi dtSN S'NS
| trolytically, collected in a gas holder
| compressed to about $50 atmospheres
dried and stored in cylinders. The
gas holder used contains machine Gil
| in place OF water, TO diminish the
entrance of air through the liquid.
The iiquefier in use produces about
two liters OF liquid per hour. The
| liauid hydrogen can be preserved for
| a day or two in slivered glass
vacuum walled containers"
| Many have wondered IL the ad-
vanced methods OF obtaining new low
| temperatures could not be used in the
| matter of refrigeration. and numerous
| inventors throughout the land have
been striving for a method of obtain
| ing low temperatures that would
| permit of a longer duration OF cold
than is secured by the methods as
| applied today. When Prof. Kanolt
was asked if this was one of the
| thoughts that the scientists Of the
bureau had in mind he said:
| The Importance of liquid hydro
gen lies in it's use for the production
of extremely low temperatures and
the study of the properties of matter
at these temperatures. Some of these
properties are important in theoreu-
cal physics. The method has never
been used industrially."
FTER liquid hydrogen has been
"A obtained IL is comparatively easy
to freeze II 10 a solid by placing It
in a vacuum walled container and
evaporating 1t under reduced pres
sure produced by a rapidly acting
vacuum pump.
One often thinks of a cork as
substance that will float in any liquid
into which IL is thrown, but II you
throw a cork into liquor hydrogen 1t
Immediately sinks. for It's density is
about three or four times that Of
hydrogen in liquid form. This state
ment will give one an idea of what
liquid hydrogen really Is.
This is not the first time. however,
that liquid hydrogen has been made
in the United States, nor is it the
first time that II has been exhibited.
T. b. Ford, who was with the bureau
of standards, manufactured some sew
eral years ago, but the apparatus he
used was old and gave much trouble.
The first time it was shown in this
country was when Prof. Dewar ex-
hibited his product at the st. Louis
fair in 1903. Some has been made at
the University of California and a
small quantity in some laboratories
in Europe.
| There is no doubt IL a person had
asked. a few years ago, some man Of
science 70 make liquid hydrogen or
to get as near the point of absolute
zero, as is done now by Prof. Kanolt
without any trouble, the request
/ would have been considered beyond
reason. The very fact that scientists
in the employ of the United States
government can at will reach down
the tube of degrees of cold day after
day with ease is an achievement that
is envied by the men of other lands.
y y
xx1HEN you happen TO walk along
w the street and see one of those
ifunny-iooking things that the weather
people call kiosks. the place where
they put their thermometers, and you
happen to note that the mercury is
crawling upward, ever upward, and
IL has already passed the 80 mark. re
member that out at the bureau of
standards they just turn on a few
blows of temperature that is AS de-
grees below that point that we call
zero; or IL whom the coal supply runs
short this winter and you are sitting
trying to coax a degree or more out