The Valley Virginian. [volume] (Staunton, Va.) 1865-1895, 1892-08-18
The Making of Ice.

| Inc pfIDclple on WHICH Tie lnanuIaC
ture of ice is based is exemplified in til
relation of heat to the conversion Q
] water into gaseous steam. A certain
amount of heat is required for the con
version of any fluid into a gas. Thi
I heat becomes, as we say, latent-that
being employed for the time in produc
ing violent undulations of the gas mole
| cules.
Whenever liquid is converted into
gas, heat must come from somewhere
In the making of steam it comes from
the fire; in the ordinary evaporation 0
water out of doors, it comes from tn,
sun. When there is no special heating
arrangement, but the conditions arr
favorable for the gaseous change in the
fluid, heat will be taken up from sur
rounding substances if they have any
If you dip your hand in water, and ther
wave it through the air, the water will
evaporate-that is, be converted into gas
and you will appreciate by the coo
sensation that heat has been abstracted
from your hand. If you use instead Of
water some fluid which more readily
passes into the gaseous state, such as
alcohol or ether, the sensation of cool
ness will be more immediate and intense
Now this is the principle which is ap-
piled in the manufacture of ice. Some
fluid which evaporates readily is forced
to do so under such conditions that the
heat which it must have and render
latent in its vapor will be extracted from
limited quantity of water, and this
process being made continuous, so much
heat will finally be distracted from the
water that its molecules can no longer
stay mobile, but fly together into crys-
tals-the water freezes.
The evaporating fluid used in practice
may be sulphuric ether or sulphurous
acid or ammonia The last is perhaps
nowadays most often used. These fluids
are kept in strong. close pipes and re
ceivers, and can under no conditions
come into contact with the water to be
frozen.
Suppose we consider the ammonia
freezing machines very briefly only, for
into the details of the process it is not
necessary for US here to enter.
But in order to understand this ope-
ration one more physical principle must
be stated which is that the degree of
pressure to which substance is exposed
has a great Influence upon the tempera-
ture at which it passes from the fluid to
the gaseous condition. Water at the or
binary altitude boils-that is, is con-
verified into vapor-at 100 degrees cent?
grade (212 degrees Fahrenheit). But on
a high mountain it will boil at a lower
temperature than this, because the ats
mospheric pressure is less there.
On the other hand, if you put gas into
a receiver, and expose it to a sufficiently
heavy pressure by a powerful pump, or
become fluid forthwith, and the heat
which had been latent in it will be given
out Now this in a general way is what
is done to the ammonia in getting it
lOnuy w llCCZC WttbCf. uIC III uIU JILL
monia boils-that is, passes from the
liquid into the gaseous state-at a tenn
perature about 2l0 degrees Fahrenheit
lower than water does. Hence ammonia
is a substance which at ordinary tenn
peratures is a gas. That which we buy
at the drug stores as ammonia is simply
solution of the gas in water and from
this, as everybody knows, it is readily
given off. 1t is volatile, that is; it tends
under ordinary circumstances to get into
the gaseous form. Now in ice foctories
powerful engines are used to force the
ammonia gas by pressure into the liquid
state, and the heat which is thus set free
is carried off by cool water pouring over
the coils OF stout iron pipe in which it
is confined. This fluid ammonia-kept
fluid by the pressure to which it is sub
jected a pressure varying from 1875 to
IT'S pounds to the square inch-is carried
in pipes to coils in the freezing tanks.
These tanks are simply great watts filled
with brine, and covered over with a
floor. Into this brine, cans filled with
the water to be frozen are placed and
ually between three and four feet deep,
about one foot thick, and nearly two
feet wide. Coils of pipe communicating
with the ammonia pipes are immersed
in the brine, which is kept in motion by
paddle wheels moved by machinery.
The brine acts as a carrier of the heat
from the water in its tight metallic cans
to the ammonia pipes. Brine is used
because it does not as readily freeze as
water does, and acts as good conductor
or distributor of the heat.
Now, when all is ready, the fluid am
monia under its great pressure is allowed
to escape into the coils of pipe which
pass about in the brine, and in which
the pressure is so much less that the
ammonia as it rushes in becomes at once
a gas. But to do this it must have heat
1t MUST HAVE IT. From the walls of
the pipes into which it rushes, 1t seizes
it first. These take it from the brine
which bathes them until it's temperature
goes down, down, and it begins to draw
through their iron walls upon the heat
stock of the water in the cans. And so
the mimic but relentless warfare goes
on. The ammonia vapor. is constantly
pumped away from the cold pipes in
which it had expanded to be used over
again, while fresh liquid ammonia is as
constantly forced in from behind.
Some hours pass and the heat stock in
the water is growing scantier and scant-
Ter. 1t can stand it i'll this way but little
longer; it is down we'll nigh to zero cen
Upgrade, and the wild Unsuitable vapor
raging for heat in the pipes not far off
is still sucking it away. The only thing
which can be done now to furnish more
is for the water to give up its latent
heat and that is to sign it's own death
warrant as water; for, if one may use
such turn of phrase, without its latent
heat water is ice.
Well, at last there is nothing for it,
and that happens which is happening
this clear wintry night ON which l write
at the edge of every lake and pool and
4 Ia