LIQUID An. AND ITS POSSIBILITIES
machinery used by Mr. Tripler of New York in his researches
are by no means complex.
The plant of the latter consists of one sixty horse power engine
which drives a triple compressor. The air in the first cylinder
being compressed to, one hundred pounds pressure per square inch;
in the second cylinder to eight hundred pounds; in the third
cylinder to two thousands pounds per square inch.
The air is then passed through cooling pipes surrounded by
water in order to dissipate the heat generated during compression.
It then passes through copper coils enclosed in a cylinder packed
with some non-conducting material which prevents the heat of the
atmosphere from reaching the coils.
At the terminus of each coil is a needle-point opening through
which the air escapes and thereby allowed to expand to a pressure
of fifteen atmospheres. The expanding air produces a sufficiently
low temperature to convert one-third of the air into a liquid
which is collected in the bottom of the cylindrical jacket and can
then be drawn off through a tap as just so much water. By this
means Mr. Tripler is able to obtain liquid air fifteen minutes after
starting.
It is said that the first ounce of liquid air obtained in an Eng
lish laboratory cost $3,000, yet by this process of Mr. Tripler the
cost has been so greatly diminished that one gallon can be had for
$4.
Liquid air when once obtained cannot be confined with any
safety unless by special precaution. It boils at--191° C. and when
we think that eight hundred cubic feet of air is condensed into
one cubic foot of liquid, an equivalent of 12,000 pounds pressure
per square inch to produce, a faint idea can be had of the amount
of latent energy stored up. Upon evaporation of the liquid when
in confinement only 10,000 pounds pressure is realized.
Prom this fact can be readily seen the great advantage gained
by this method of converting mechanical energy into a transfera
ble form and then using it at some distant point for a motive
power.
It can be dipped up by a cup, handled and poured as easily as
water, but when it is thus treated evaporation takes place at a
very rapid rate. Large quantities, six to ten gallons, have been
shipped from New York to Boston and to Washington by simply
placing the liquid into a milk can which is protected from the