The morning news. [volume] (Savannah, Ga.) 1887-1900, 1892-08-06

under no conditions come into contact with
the water to be frozen.
Suppose we consider the ammonis freez-
lug machines very briefly only, for into the
details Of the process it is not necessary for
US here to enter.
But in order 20 understand this operation
one more physical principle must be stated,
which 10 that the degree of pressure to
which a substance is exposed has q great In
fiuence upon the temperature at which it
passes from the fluid to the gaseous condi-
ton. Water at the ordinary attitudes
boils-that is, is converted into vapor-at
1909 centigrade (2l2' Fahr.), But on
high mountain it Will boil at lower
temperature than this, because the atmos-
pheric pressure is less there.
On the other hand, If you put gas into
a receiver, and expose 1t to a sufficiently
heavy pressure by powerful pump, or in
some other way, it will in most cases be-
come a fluid forthwith, and the heat which
had been latent in it will be given out Now
this IN general way is what is done 20 the
ammonia in getting 1t ready to freeze
water. Pure liquid ammonia boils-that is,
passes from the liquid into the gaseous
state-at temperature about 400 Fair.
lower than water does. Hence ammo
MIA Is a substance which at ordinary tenn
peratures is gas. That which we buy at
the drug stores as ammonia is simply solu-
-
every one knows. it is readily given of. 1t
Is VOLATILE that is, it tends under ordinary
conditions to get into the gas
eous form. Now In ice factories powerful
engines are ased to horce 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
ammonis-kepU fluid by the pressure to
which it is subjected, a pressure varying
from 125 to IFS pounds to the square inch-
is carried in pipes co coils in the freezing
tanks. These tanks are simply great watts
filled with brine. and covered over
with floor. Into this brine, cans
filed with the water to be frozen are
placed and carefully covered These cans
| are usually between three and four feet
deep, about one foot thick, and nearly two
feet wlde Coils of pipe communicating
with the ammonia pipes are immersed in
the brine, which is kept In motion by pad-
dle-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
| sure is 30 much less than the ammonia as it
rushes IN becomes at once gas. But to do
| this it must have heat. It must have 1t.
From the walls of the pipes into which
| it PUSHES it seizes it first. These
take it from the brine which battles them
| until its temperature goes down, down, and
it begins to draw through their open walls
| upon the heat stotk of the water in tie 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 III
the water is growing scanter and scantier.
IL can stand it in this way but little longer;
1t is down we'll nigh to zero centigrade, 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. aud 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 10, and
that happens which is happening this clear
wlntor night on which write at the edge of
every lake and pool and pond out of doors
hereaoouts-little transparent spiculse shoot
out from the cooled surfaces, and the wa ter
| slowly, as If unwilling, yields itself into its
| crystal bonds. The ice layers on all sides
slowly thicken, aad st last In about sixty
hours, all is solid. The watchtul attendant
raises with a crane the great beautiful ice
block, still in its galvanized iron can, out Of
its cold bath and trundles it off to make
way for another molecular battle and az
| other victory