The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1903-03-01
Truth About
Liquid Air

lin, which go far to dissipate the ex.i
traVagant theories launched concern
ing this form of power by the Ameri-
can press, and which, according to
DR.. Lindes belief, ,cwin never be real
lied. ~ No .-.,of. .t
According to many enthusiastic stor-
les which have appeared, liquid air was.
to be the future power of the world,
but from DR.. Lindes deductions 1t does
not appear to have any very impor-
tant purpose in the present economy
of things. t...
DIR. Linde explained that it would
not be economical to employ. it in cold
storage work, because when you want
a few degrees below the freezing point
of water it is not economical to pro-
duce a $50 degree Fahrenheit below.
Power has to be expended in produce
ing cold and the power is roughly pro-
portioned to the degree of cold pro-
duced. AS DR.. Linde observed, LIQUID
air in small quantities would, be very,
useful for cooling dining or ball rooms.
In such cases as these the quantity of
liquid air would be so small that the
high price at which 1t was produced
would not matter.
The liquid air of commerce is pro-
duced from ordinary atmospheric air,
by a continuous process Of compress
ing and cooling. Every substance, it
Is supposed, may exist in one of the
three states, the solid, the LIQUID or
the gaseous, according to the surround
ing conditions. --'---.--
Each state presupposes the presence
of a certain quantity Of heat in the
substance. Thus, in the solid form q
smaller quantity of heat is actually in
the substance itself than In the LIQUID
form, while again, a smaller quantity
of heat is present in the liquid form
than in the gaseous. By the addition
l. l.
stance in sufficient quantities the state
of the substance will be changed Be
yond this, the three. forms in which
substances may exist mean that the
molecules, the very minute parts of
the substances, are very much closer
together in the solid form than in the
liquid form, and in the liquid form
they are much closer together than in
the gaseous form.
Therefore, in order to liquify a gas
two things are necessary, the closing
up. as it were, of its molecules, and
the extraction of certain quantity Of
heat from II.
When air is compressed, as In. those
cases where compressed air is used for
mechanical purposes, heat Is generated
in the air, in the act eof compression
1t represents a portion of the work
done upon the air by the compressor
This heat has to be extracted as well
as the heat possessed by the air., in
virtue of it's condition as a gaseous
mixture before it can be liQuified. Thus,
in the process of making liquid air,
the air is continually compressed by
successive stages, and continuously
cooled, very pretty device being made
use of in the cooling, by which the air
that has been cooled to certain de-
gree is made to cool air that has not
reached that point, so that the effect Is
nm Iglf Il Vino lfr.Y,A fra
ton is reached, the air In its liquid
form looks precisely like, water, and
can be poured out just as water is,
with certain precautions. The liquid
air being, however. at such an ex-
tremely low temperature, renders It
dangerous to touch, and must be ham
died just as are hot bodies In the
case Of very cold bodies heat passes
from the hand to the object at q very
rapid rate just as 1t passes from q hot
body to- the hand, It is the rate at
Which the heat is transferred either to
or from the human body which causes
the pain and other troubles. When
poured out on a table the liquid air runs
about in small crystal globules, Just
like mercury. disappearing in short
time or returning to gaseous form. IL
allowed to escape into the atmosphere
It's presence IS manifested by clouds Of
mist, producing the impression that the
liquid air ts' converted into fog, This
is not SO, however. What actually
happens Is the aqueous Vapor which Is
always present In the atmosphere, par
tlcularly that of rooms in which a mum.
Der OF people are assembled, condenses
and then freezes and forms a sort OF
a boar frost, which is what we see
and not the liquid itself. Liquid all
SEXES every opportunity Of returning
to the gaseous condition. but 1T can
Inv oIafiY r.
surrounding bodies. When it Is allowed
to escape into the atmosphere 1t ex-
tracts the heat from the air into which
1t passes, the atmospheric air of the
room, In the immediate neighborhood of
the orifice from which it is escaping
Ih1s lowers the temperature of the air
at that point, and with lowered tenn
perature it is no longer able to main
tain so much aqueous vapor in sus-
pension The vapof is deposited as
water and then freezes. The same
action In a minor form may be seen in
any cold storage engine house, where
the cold pipe Is covered with snow
The method adopted for storing liq-
u1d air, devised by Prof. 'Dewar, is one
of the most novel arrangements that
has been seen in the domain of physics
for long time. The air Is stored in
glass bottles, each bottle consisting of
two distinct bottlesj separated by a
vacuum, maintained at a high fig
ure as 1t is possible to obtain. In ad-
dition, the outside of the outer bot
tie is silvered all over with mercury.
The object Of the arrangement is to
prevent the access of heat to the liquid
air inside the inner bottle. The vac
uuln space offers a very high resistance
to the passage of heat waves through
or across 1T, and the mirror formed by
the mercury on the outside of the outer
bottle reflects the heat waves away
from the bottle. The mouth of the
bottle Is left open to the atmosphere,
and 1T was stated by DR.. Linde that q
| charge Of liquid air would last four
teen days. During this time the charge
Is slowly disappearing by evaporation,
by reconversion to the gaseous form,
| from the passage Of heat to the liq-
! uid. Closed bottles cannot be used, as,
| 1t being impossible to exclude COM
| pletely heat from the liquid air, the
| latter would be slowly changing into
| the gaseous state, and in so doing. Gre
| atlng pressure within the bottle
which no vessel could withstand which
would also resist the passage of heat
| through its walls. The final pressure
! was given by DR.. Linde as 10000
| pounds per square inch, when all the
| liquid had returned to the gaseous
! form. This is the reason why steel bot
| ties cannot be employed as they are
for carbonic acid gas, ordinary COM
] pressed air and so on. -r
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