El Paso daily herald. (El Paso, Tex.) 1881-1901, 1898-06-25
HOW AIR IS LIQUEFIED.
The Process Which Mr.. Tripler En-
ploys.
New York Tribune.

markable commodity. People have
heard about eggs and onions frozen al
hard as rocks after being immersed in
little of this fluid; of steel burning al
above zero in a tumbler containing Ii
quid oxygen whose temperature was
about 5000 degrees below zero: of the
delicate white vapOr given off by air
when passing from q liquid to ga
seous state, and of the explosive pro-
perties which were developed when q
teaspoonful of Mr.. Tripler's magic
preparation was confined in a metal
tube. Less attention. however, has
been given to the process by which air
is liquefied and to the possible indus
trial uses OF the new product.
Dewar and other chemists who re-
duced air to liquid form years ago
did SO in q very costly fashion and by
q complicated process. Mr.. Tripler,
employing precisely the same princi-
Piles as they did, simplified the opera
tion. A German, Linde, has BEEN fol-
lowing practically the came plan as
Mr.. Tripler for two or three years,
and his apparatus has been extensively
described in foreign prints during that
time. Mr.. Tripler claims, never
theless, that he anticipated Linde, and
took out patents long before the latter
published any account of his proce-
dure.
The first step in the process is to
compress air by just such q compressor
as is used in connection with pneumat-
ic guns and traction systems. A piston
in q cylinder squeezes quantity of air
into smaller compass than that 1t or
dinarily occupies, and the compressed
air then flows out through valve GO
second cylinder. where it is compressed
some more. Finally it is stored in Q
- 10 Oh aI
that this operation is just the reverse
of that which occurs in q steam engine
In the latter Instance vapOr, already
held in Q boiler at high pressure, is al
lowed to enter q cylinder, and by ex-
pausion to do work. Double, triple
and even quadruple expansion il re.
sorted to before the steam completes
Its work. In like manner double and
triple compression are employed with
air. Higher pressures, though, are
carried in storage tanks containing air
than in steam boilers. The Hardie
railway system stores air at 1000
pounds to the square inch, and puts it
into the car reservoir at 1000 or $500.
Steam boilers, even in marine prac-
tice, rarely show pressures above 150
and 200 pounds to the inch.
Compression heats a vapor and ex-
papsion cools it. Every compressor,
curled up in q water tank whose con-
tents are constantly changing, through
which the compressed air must pass on
its way to the storage tanks in order to
cool Il. This removal Of the superfu-
Gus heat 10 particularly necessary when
air is to be liquefied.
1t is only the second step, the one
about to be described, that is at all
peculiar or novel in MIR. Tripler's
II -
R Rhieb he &c call. lis p'eci is 9 He
does not publish all the details OF its
arrangement. But both he and Linde
tell enough to satisfy the curiosity of
the general 3public. The sprinciple of
it is exceedingly simple. He uses the
''cold of expansion" obtained from
part of his stock of compressed air, to
reduce the temperature OF the rest of
it.
A long, spiral coil of very stout pipe
is inclosed in Q cylinder. For convent
ence, 1: may be assumed that the de-
vice stands on end. To the upper ex-
tremity of the coil is led a supply pipe
from the storage tank. Air enters the
coil, then, at the same pressure that ex-
lists in the latter. Linde conducted
some of his earlier experiments with a
pressure OF 900 pounds, but now uses
nearly 5000. Tripler employs from
1000 to 1900. AT the lower end of the
coil is q valve Of such design that when
opened 1t permits limited quantity of
the air to escape into the cylinder.
There 1t instantly expands, and its
temperature is greatly reduced by the
process of expansion. Neither Tripler
nor Linde allows the air to attain or
binary atmospheric variety. Both of
them still keep it under pressure. Lin
de expanded down to 300 pounds when
he started with 900. Tripler expands
from 2. 800 down to 700. Thus an i'm
mense reduction of temperature Is
secured in the space within the cylin-
der, but outside the coil. Gradually
the cold expanded air abstracts some
of the heat OF the compressed air in
side the coil. There is q tendency to
equslize the temperatures inside the
coil and outside. And it will be seen
that the air in the coil grows colder as
it passes from the upper to the lower
end, while the outer current of air,
which moves in q reverse direction, be-
comes warmer and warmer as it sp-
proaches the top.
Now, the fall in temperature from
expansion amounts to q certain num-
Der of degrees for q certain difference
of pressure. AT first the starting
point from which the fall occurs In
the chamber outside the coil is the
temperature of the air coming from
the storage tank, which may be sssum-
ed to be 80 degrees Fahrenheit.
But after the chilling effect
of the bath of expanded air is
left on The air inside of the coil,
then the starting-point Is lower than
before. The air which escapes from
valve i've minutes after the operation
began falls only as many degrees as
that which escaped at first, but it
reaches lower temperature level, be-
cause 1t started from . lower one. Ten
minutes after the valve is opened the
air in the coil is still colder, and the
s'cold of expansion" around it is still
more extreme. In other words, the
process is Cumulative" And usually
by the end of twenty minutes small
usntity of the air in the bottom of the