IMPROVEMENTS IN REDUCING THE TEMPERATURE OF AIR, IN PRODUCING ICE, IN PRESERVING ANIMAL AND VEGETABLE SUBSTANCES, AND IN APPARATUS THEREFOR
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Robert Little at the Office
of the Commissioners of Patents, with his Petition, on the 25th
March 1868. A communication from abroad by Dugald Little,
residing at Hobart Town, Tasmania.
I, ROBERT LITTLE, of Greenock, in the County of Renfrew, North
Britain, Merchant, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN REDUCING THE TEMPERATURE OF AIR, IN PRODUCING
ICE, IN PRESERVING ANIMAL AND VEGETABLE SUBSTANCES, AND IN APPARATUS
THEREFOR," which Invention has been communicated to me from abroad
by Dugald Little, residing at Hobart Town, Tasmania, to be as follows,
that is to say:-
This Invention has principally for its object to preserve animal and
vegetable substances, and to admit of otherwise perishable food being
transported in a preserved state from localities, such as the Australian
colonies, where it is produced in large quantities and at a cheap rate
to such places as the United Kingdom, where the supply of food is
comparatively deficient and its cost high.
The Invention consists, firstly, in cooling air by submitting it in a
compressed state to cold or cooled water in apparatus constructed like

page_text: any suitable kind of surface condenser, such as is in use with steam
engines; secondly, in employing the cooled compressed air to maintain
as low an atmospheric temperature as may be required in a room, ship's
hold, or other closed vessel or receiver, by admitting it and letting it
expand therein; and, thirdly, in freezing and thereby preserving animal
and vegetable substances by placing them in such room, ship's hold,
or other closed vessel or receiver, cooled to the requisite low temperature
by the expansion therein of cooled compressed air. The air used should
be as dry as possible, and when necessary it is dried by passing it
through or over strong sulphuric acid either before compression or when
compressed, or it may be dried in any other convenient way. The
compression may be effected by any convenient kind of pump. The water
or liquid which is made to circulate through the condenser to cool the
compressed air, or in other words, to remove the heat which the.com-
pression renders sensible, is by preference itself cooled so as to increase
its effect. This cooling of the water may be effected by any convenient
known means, but it is preferred to bring it about by passing the water
through a closed vessel in which there is a quantity of concentrated
sulphuric acid and from which the air is exhausted, when evaporation
of a portion of the water will take place and will have the desired cooling
effect. The closed room, hold, vessel, or receiver in which the cooled
compressed air is to expand must be provided with ventilators, lightly
loaded valves, or the like, to allow the lighter and warmer portions
of the contained air to escape and make room for the fresh air supplied
from the compressing and cooling apparatus. When a ship conveying
preserved food is provided with the air compressing and cooling apparatus
the hold or closed space containing the food may be continuously or
intermittently replenished with fresh cooled air so as to maintain the
requisite low temperature throughout the voyage.