" In freezing-mixtures, the substances com-
bined have such an affinity for each other that
when intimately blended they combine chemi-
cally, and in so doing liquefj^ The operation
should be so arranged that no heat be furnished
either by the vessel in which the liquefaction
takes place, or from anj^ external source. Under
such circimistances the heat absorbed during
the liauefaction must be furnished by the ma-
terials of the freezing-mixture or by the body
which it is intended artificially to cool or to
freeze.
" Many recipes are to be met with for freez-
ing-mixtures. One or two examples will suffice
here. With equal weights of fresh snow (or
pounded ice) and common salt, a temperature
of — 4 degrees Fahr. can be maintained for
many hoirrs. A mixture of three-parts cry-
stallised chloride of calcium and two parts of
snow will produce a depression of temperature
sufficient to freeze mercury. If the vessel in
which the materials are to be mixed and the
chloride be cooled to 32 degrees a temperature
of — 50 degrees can be produced. The most
powerful fi-eezing-mixture is formed by dis-
solving solid carbonic acid or solid nitrous oxide
in sulphuric ether. For more moderate tem-
peratui-es, certain salts, easily procurable, may
be used. Thus, four ounces of nitre and four
ounces of sal-ammoniac, both in fine powder,
mixed with eight ounces of water, will reduce
the thermometer from 50 degrees to 10 degrees.
Equal parts of water, of powdered crystallised
nitrate of ammonia, and of powdered crystallised
carbonate of soda wiU lower the temperature
from 50 degi'ees to — 7 degrees."
Even in hot climates ice may be produced
xmder favourable circumstances by evaporation.
Xear Calcutta this is managed on the open
plains by exposing a thin stratum of water to
the atmosphere during the fine clear nights of
December, January, and Februarj\ The pans
are composed of porous earthenware, and water
is poiu-ed in to the depth of about an inch and.
( 724 )
a half. A large number of these vessels arc
arranged in an excavation in the ground, be-
tween thirty and forty feet square, and with a
depth of two feet, the bottom being covered to
the depth of ten or twelve inches with the
stalks of Indian corn or with sugar canes.
These pans are visited at sunrise, and the ice
is separated from the water, and packed as tight
as possible in a deep cavity or pit, well screened
from the heat.
Refrigeration, Food Preserved by,
— " Refrigeration as applied to animal sub-
stances, with a view to their preservation, is an
important subject, though, strictly speaking, a
substance temporarily kept from decomposition
by being surrounded by a temperature suf-
ficiently low for the purpose, can hardly be
called 'preserved food,' as by this term is
generally meant an article preserved in a re-
ceptacle, or otherwise, which is not subject to
decomposition through atmospheric influences.
The first patent for the preservation of food
by means of refrigeration was taken out in
1845; since that time many expedients have
been adopted by the use of ice, and by arti-
ficial methods of lowering the temperature
by evaporation, Avith a view to the impor-
tation of fresh meat from Australia, America,
and elsewhere into this country.
Page 1507
Presented as published in 1892. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
" In freezing-mixtures, the substances combined have such an affinity for each other that when intimately blended they combine chemically, and in so doing liquefj^ The operation should be so arranged that no heat be furnished either by the vessel in which the liquefaction takes place, or from anj^ external source. Under such circumstances the heat absorbed during the liquefaction must be furnished by the materials of the freezing-mixture or by the body which it is intended artificially to cool or to freeze.
" Many recipes are to be met with for freezing-mixtures. One or two examples will suffice here. With equal weights of fresh snow (or pounded ice) and common salt, a temperature of — 4 degrees Fahr. can be maintained for many hours. A mixture of three-parts crystallised chloride of calcium and two parts of snow will produce a depression of temperature sufficient to freeze mercury. If the vessel in which the materials are to be mixed and the chloride be cooled to 32 degrees a temperature of — 50 degrees can be produced. The most powerful freezing-mixture is formed by dissolving solid carbonic acid or solid nitrous oxide in sulphuric ether. For more moderate temperatures, certain salts, easily procurable, may be used. Thus, four ounces of nitre and four ounces of sal-ammoniac, both in fine powder, mixed with eight ounces of water, will reduce the thermometer from 50 degrees to 10 degrees. Equal parts of water, of powdered crystallised nitrate of ammonia, and of powdered crystallised carbonate of sodawill lower the temperature from 50 degrees to — 7 degrees."
Even in hot climates ice may be produced under favourable circumstances by evaporation. Near Calcutta this is managed on the open plains by exposing a thin stratum of water to the atmosphere during the fine clear nights of December, January, and Februarj\ The pans are composed of porous earthenware, and water is poured in to the depth of about an inch and
( 724 )
a half. A large number of these vessels arc arranged in an excavation in the ground, between thirty and forty feet square, and with a depth of two feet, the bottom being covered to the depth of ten or twelve inches with the stalks of Indian corn or with sugar canes. These pans are visited at sunrise, and the ice is separated from the water, and packed as tight as possible in a deep cavity or pit, well screened from the heat.
Refrigeration, Food Preserved by, — " Refrigeration as applied to animal substances, with a view to their preservation, is an important subject, though, strictly speaking, a substance temporarily kept from decomposition by being surrounded by a temperature sufficiently low for the purpose, can hardly be called 'preserved food,' as by this term is generally meant an article preserved in a receptacle, or otherwise, which is not subject to decomposition through atmospheric influences. The first patent for the preservation of food by means of refrigeration was taken out in 1845; since that time many expedients have been adopted by the use of ice, and by artificial methods of lowering the temperature by evaporation, Avith a view to the importation of fresh meat from Australia, America, and elsewhere into this country.