The Wilmington daily Republican. (Wilmington, Del.) 1890-1902, 1892-08-20
ICE.
SIMPLE EXPLANATION OF HOW
ARTIFICIAL ICE IS MADE.


ARTIFICIAL ICE IS MADE.
Tho Principle of Ammonia Freezing Ma
chimes Very Clearly Set Forth-The
Factor That Heat Is in Producing Cold,
The Part That Pressure Plays.
The principle on which the manufacture
Of ice is based is exemplified in the relation
Of heat into the conversion of water into
gas steam. A certain amount of heat is
required for the conversion of any fluid
into gas. This heat becomes, as we say
latent-that is, is being employed for the
time in producing violent undulations oil
the gas molecules.
Whenever a liquid Is converted into Q
gas, heat must come from somewhere. In
the making of steam 1t comes from the
fire; In the ordinary evaporation Of the
water out of doors It comes from the sun
When there is no special heating arrange
ment, but the conditions are favorable fol
the gaseous change in the fluid, heat will
DO taken up from surrounding substances
II they have any.
II you dip your hand in water and then
wave it through the air the water will
Ievaporate-thatis is, be converted into gas
and you will appreciate by the cool sensa-
ton that heat has been distracted from
your hand. II you use instead of water
some fluid which more readily passes into
the gaseous state, such Is alcohol or ether
the sensation of GOODNESS will be more i'm
mediate and intense.
Now this is the principle which is ap
piled in the manufacture of ice. Some
fluid which evaporates readily is forced tC
do SO under such conditions that the heat
which it must have and render latent il
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 mole
cules can no longer stay mobile, but fly to
gether into crystals-the water freezes.
The evaporating fluid used in practic,
may be sulphuric ether or sulphurous acit
or ammonia. The last is perhaps nova
days most often used. These fluids arr
kept in strong, close pipes and receivers
and can under no conditions come into con
tact with the water to be frozen.
Suppose we consider the ammonia freez
ing machines very briefly only, for into tn,
details of the process it is not necessary TO
us here to enter.
| But in order to understand this opera
tion one more physical principle must b
stated which Is that the degree of pressur,
to which substance is exposed has grea
influence upon the temperature at which
| it passes from the fluid to the gaseous con
dition. Water at the ordinary attitudes
boils-that is, is converted into vapor-ai
100 degs. centigrade (212 Fahrenheit)
But on high mountain it will boil at
lower temperature than this, because tn,
atmospheric pressure is less there.
| On the other hand, if you put gas int,
a receiver, and expose it to sufficient,
heavy pressure by a powerful pump or II
some other way, it will in most cases be
come fluid forthwith, and the heat which
had been latent In it will be given out
Now this in general way is what is don,
to the ammonia in getting 1t ready t,
freeze the water. Pure liquid ammoni;
boils-that is, passes from the liquid int,
the gaseous state--at a temperature abou
240 dogs. Fahrenheit lower than waite
does. Hence ammonia is su bstance which
at ordinary temperature is gas. Tha
which we buy at the drug stores as am
monia is simply n solution of the gas ii
water, and from this, as every one knows
it is readily given off. 1t is volatile, tina
| is, 1t tends under ordinary conditions t,
get into the gaseous form.
Now in ice factories powerful engine
are used to force the ammonia gas b,
pressure into the liquid state, and the heal
which is thus set free is carried off by coo
water pouring over the coils of stout iror
pipe in which it Is confined. This fluit
ammonia-kept fluid by the pressure tt
which it is subjected, a pressure varying
| from 1875 to lT5 pounds to the square incl
lis carried in pipes to coils in the freez
ing tanks. These tanks are simply grea
watts filled with brine and covered owe
with a floor. Into this brine, cans fllleC
with the water to be frozen are placed ant
carefully covered. These cans arc usual,
between three and four feet deep, abeu
one foot thick and nearly two feet wide
Coils of pipe communicating with tn
ammonia pipes are immersed in the brine
which is kept in motion by paddle wheel
moved by machinery.
The brine acts as carrier of the hea
from the water in its tight metallic can
to the ammonia pipes. Brine is used b.
cause it does not as readily freeze as waite
does and acts as good conductor or di
tributor of the heat.
Now, when all is ready, the fluid an
monia under its great pressure is Above
to escape into the coils of pipe whic
| pass about in the brine, and in which til
pressure is SO much less that the ammoni
as it PUSHES in becomes MT once gas. Blu
10 do this 1t must have heat. 1t must hay
= it, From the walls of the pipes into whic
/. it rushes it seizes it first These take
s from the brine which bathes them unt
its temperature goes down, down, and
, begins to draw through their iron wal
!, upon the heat stock of the water in til
Jeans And so the mimic but relentle.
warfare goes on. Tho ammonia vapor
constantly pumped away from the col
lpipes in which it had expanded to be use
over again, while fresh liquid ammonia
, rs constantly forced in from behind.
Some hours pass, and the heat stock /
/ the water is growing seantier and scantie
1t can stand it i'll this way but little longe
/ it is down we'll nigh to zero centigrad
and the wild, Unsuitable vapor raging fl
heat in the pipes not far off is still suckin
1t away. The only thing which can |
done now to furnish more is for the wat,
to give up its latent heat, and that is
f, sign its own death warrant as water, 70
). if one may use such turn of phras
J. without its latent heat water is ice
4 The ice layers on all sides slowly thicke
d and at last, in about sixty hours, all
solid. The watehful attendant raises vii
a crane the great beautiful ice block, SIT
n its galvanized iron can, out Of its co
!. bath, and trundles it off to make way f
i tanether molecular battle and another vi
!. tory.-T. Mitchell Prudden in Harpers.
u
u A Picture of tho Virgin.
:, II In q church at Capua there is lar
. painting of the annunciation Of the yirg