The capacity of a refrigerating machine is based upon the weight of ammonia in the gase ous form which it can discharge in 24 hours, each pound of gas representing a certain quan tity. of heat-absorbing power. The unit of ca pacity is the refrigeration which would be ac complished by the use of one ton of ice. Such a quantity will lower the temperature of 28,400 pounds of water 10 degrees. Therefore, if a one-ton)) machine is employed, it will cool 197% pounds of water to the extent of one degree a minute. Tests made of the York type machines of this capacity show that one will keep the °curing') department of a pacicing house containing 12,000 cubic feet of space, at a temperature of 40° F. or 1,500 cubic feet at zero. In other words, it is sufficient to keep 10 beeves or 25 hogs chilled at the former tem perature. As a single plant used in the large pacicing-houses and breweries may represent 500 tons capacity, it will be seen that the cold storage compartments are maintained on a very elaborate scale, a single one containing thou sands of carcasses. The horse power required for one of these large machines aggregates 625. The air-compressors are built in various de signs, and are known as single and double acting. A recent invention, the Westinghouse Leblanc ref rig.eration machine, represents a new process that is now being introduced, which involves the use of water vapor for producing a temperature of from 35° F. to 50° F.
In large cold-storage warehouses the floors are not over eight or nine feet high. The pipe is attached to the v.-ails, and in wide rooms to the sides of posts running through the middle of the room, so that an equal temperature can be maintained in all portions. In others, like fish-freezing rooms, the pipes are even used as shelves to hold the tins filled with fish, which are frozen into bricks and piled away in another compartment. Poultry and game are also kept in a frozen state, and the meat remains almost as hard as stone while in the cold room. But ter also is kept at a temperature near zero, which is said to preserve the flavor contained in its volatile oil, so that it is equal to fresh butter. Eggs are preserved sometimes from two to six months, but require particular care. The air in the room should be neither too moist nor too dry, and the chamber should be neither without ventilation nor supplied with too much, as then the eggs would lose in weight on ac count of their liability to evaporate through the shell. Eggs, butter and milk are also liable to be tainted by any smell arising from the wood work, or articles stored in the neighborhood, and the rooms have to be constructed and ar ranged with this point in view.
The above, it may be said, have been prob lems for the cold-storage experts to solve by practical experiments; but food products can be preserved in properly constructed houses with as little difficulty as any other articles. In the preservation of meat, from the time that the beef, sheep or hog is killed, it is kept in cold storage or "chill" rooms, until the time that it is taken from the refrigerator to be prepared for the table. The °chill') rooms are used to take the animal heat out of the meat, and reduce its temperature from about 98° F. to cold-storage temperature, that is, from 32° F. to 40° F. For this purpose the meat is hung on rails in rooms which have chambers in the upper part over the rails for ammonia or brine piping, which reduces the temperature to a point near freezing before the meat is put in. After the meat is put in, the animal heat it still contains raises the temperature in the room, but this is again gradually lowered, in the course of 24 to 48 hours, to the proper degree for re frigeration. This length of time is required in order to chill the meat thoroughly. Should it become chilled on the outside and remain warm in the centre, the centre part of the meat would be spoiled. From the "chill') room the meat
is run into the cold-storage rooms and hung on rails, where it is kept until such time as it is to be shipped. The choicest pieces are kept at least four weeks in cold storage, as the quality is thus improved, and, if the rooms are kept clean, these pieces will taste better than meat which has been recently slaughtered. For this reason, not only slaughter-houses, but depots of packers and other buildings where meat is kept in cold storage, even to small butcher es tablishments, are preferably cooled by refriger ating machinery, owing to its drying and clean liness.
In some of the large hotels refrigerators cooled by machinery are even placed close to the ovens or ranges where the viands are prepared for consumption, the refrigeration being main tained at the proper standard despite the out side temperature. High temperature is also the rule in candy factories, but manufacturers of chocolate candy have been using refrigerating machines for some time. They are forced to do this, as the compound is apt to become soft in hot weather, which, of course, would spoil the appearance of the goods for the market. The arrangement of the refrigerating piping for chocolate factories has been made in various ways. In some instances a large refrigerator is cooled in the centre of the workroom with the piping inside of it, this refrigerator being of such length that endless belting carrying tins with chocolate enters it on one side and brings them out chilled on the other. In other work rooms a series of pipe coils are simply placed along the ceiling, and the cold air coming down chills the confectionery as it is made by the employees in the same room. The chocolate is then stored in refrigerators, apart from the workroom, and there properly packed at a low temperature. After being packed it can be sent out, and ordinarily will keep for an in definite length of time.
One of the most interesting applications of cold storage, however, and one which has be come very extensive, is for preserving furs and woolens, which are kept at a temperature of not over 20° F. to keep the moths from de stroying them. These rooms have a very in teresting appearance, as among the trunks, boxes and drawers of clothing there appear figures of bears, tigers and other stuffed ani mals in threatening attitudes, put away through the hot season by their owners and taken out in the fall. Sometimes furs are left in storage continuously for several years, yet at the end of the time they are invariably found in per fect condition. Many of the trust companies in the larger cities have such cold storage com partments. In these fur and clothing rooms, where valuable carpets and rugs are also stored, the air is generally cooled outside of the room and circulated through it by means of fans.
The cold storage building erected by the United States government at Manila is probably unexcelled in scientific construction. It has a storage capacity for 1,200 tons of beef, 200 tons of mutton, 50 tons of butter, 100 tons of pota toes and 100 tons of bacon; or, in other words, sufficient food to feed an army of 10,000 men for three months. In addition to the ordinary freezing apparatus it has an ice plant with a daily output of 40 tons. The elevator, with its 2,400 pound lifting capacity, as well as most of the other appliances in the building are operated by electricity. Connecting with the elevator is an overhead tracking system extending four miles, and the mechanism is so complete that a ship landing at a near-by pier has only to open her hatches and her cargo is transported to the storage almost automatically. The power in the building is furnished by three 200-horse power engines. Consult Levey, Memoranda' (1906) ; Macintire, 'Mechanical Refrigeration' (1914) ; Cooper, M., 'Practical Cold Storage' (1914).