New Ulm review., 1911-09-27
PRESSURE: OF AIR Air.
Il May Readily Turn the Their
mometer Into a Fibber.
THE BOILING WATER POINT.

On the Scale This 10 Marked at q.
Degrees, but Under Certain condi
tions II May Be Several Hundres
Ds9ress-Ths Critical Temperature.
On an ordinary Fahrenheit thermom
eter there is written opposite 212 de
grees Boiling point Of water and op
posite SO degrees Freezing point OF
water" Neither Of these is correct eX-
cept for a certain condition of the at
mosphere, and that is when it gives on
the barometer about thirty inches, or
I fifteen pounds pressure to the square
inch. This is the ordinary pressure at
what is known as sea level, and to this
all thermometers are calibrated. In a
mountainous region the pressure is
hardly ever so much as fifteen pounds.
and water boils at sometimes as low as
200 degrees.
If water is boiled in diving bell,
where the pressure is forty or fifty
pounds square inch, its temperature
will be several hundred degrees in
stead of 212. If water is boiling in
near vacuum the temperature is so
small that the hand thrust into the
water would actually feel cold.
What has been said about the boiling
point applies to some extent to the
freezing point, but here it differs for
different materials, whereas the re-
marks about the boiling point of water
apply to the boiling points of all
liquids.
Some substances when they freeze
become larger, while others become
smaller. On this depends the freezing !
point at different pressures Of atmos-
phere. Water expands on freezing; so
do type metal and some other things
All other substances become smaller
on freezing. Water pipes burst when
the water freezes Coins of gold and
silver are stamped instead Of being
nodded, for the metals grow smaller on
freezing or solidifying, and consequent
ly the coin would be wabbly.
It has been found that the things
that expand on solidifying, as water,
freeze at lower temperature when
The pressure is increased, while the
others freeze at higher. When
substance that expands freezes under
higher pressure than usual it has to
exert more force to shove the pressure
'way, and consequently has to use up
more Of its heat energy, thus losing
more heat and becoming colder.
Take the substance that contracts
Vhen it solidifies The pressure will
elp it to get smaller, and consequent
the greater the pressure the less ,
eat it has to lose on attaining the
old state, SO 1t will freeze at higher
If the pressure is great ,
nough 1T may freeze or solidify at
degrees temperature, which
high enough to change most sub :
.ances to vapor under ordinary at
lospherfc pressure. :
This is one of the reasons advanced
, prove that the interior of the earth :,
solid, for the assumption is that the = :
ore Is made up Of substances that !,
ontract when freezing, and there is, u
course, an enormous pressure few =
undreds Of miles below the surface. Il
In regard to the boiling points of
guilds. there is an upper limit to the
oint at which thing boils-that is. "
hanges to the state Of vapor. 1t is Q
llled the critical temperature. No q
latter how great pressure exists on a
g fn 10 OF <orV @,,~ |
reater than its critical it will change r
, vapor anyhow.
The ignorance of this point held
ack the making of nquefied gases
UGH as air, carbon dioxide, etc.-for
lany years. The experimenters tried a
liquefy gases at ordinary tempera- l
Tres BY enormous pressures, whereas ;
they had just cooled the gases be- N
w their critical temperatures before t.
pplying the pressure liquefaction n
'ould have ensued Immediately.
This is the method employed today
, making liquid air. The air is COM
ressed ut first and then allowed to G
sue from small orifce, thus ex- ;
anding and cooling, is then pumped h
ack and compressed by the pump. H
lowed to 60 through the ori6ce S
gain, thus cooling still more, until at 81
lst it is below the critical tempera-
Ire, when the compression caused by
le pump liQuefies it. - Lawrence
lodges in Chicago Record Herald. 81
S>----ss->4~>s"sHs<7s-----s r
In Trouble. 81
"Yes." he said regretfully, 'T'm in a 4
ght corner. My sweetheart is wild on S