ICE

REFRIGERATION, AND COLD STORAGE. Ice has long been artificially produced in India by the evaporation of water, and natural ice and snow have from a very early date been stored for summer use or have been carried down from mountain tops to serve Jower-lying, warmer regions, but the modern industry of ice manufacture and refrigeration was born so recently as the middle of the nineteenth century. Its growth has been rapid—to-day there are in the United States alone 3000 or more plants engaged in the production of ice for general sale, in addition to the very large number employed in various industries—especially in the cold storage preservation of foods. The cold storage system, first attempted about 1860, has grown to extraordinary proportions. It has revolutionized the meat supply and extended the fruit seasons. It has rendered po ible an uniform distribution of fresh foods throughout widely diversified regions and has carried the surplus of the Americas, Asia, Austral asia, and other countries, to the markets of Europe. Together with the canning industry, it has remedied immense waste which was formerly unavoidable. It includes within our own borders a transcontinental chain of big storage houses, and refrigerator cars running from ocean to ocean, and employs great steamers especially equipped for transoceanic transportation. ‘ As would be expected, the effect of cold storage on different foods varies considerably. Meat, one of the most important articles thus cared for, is also, happily, one of the best suited for it. Frozen meat will remain wholesome for vears -almost; indefinitely. It will lose some of its flavor after the first few weeks but otherwise there is no perceptible depreciation in food value. Fish, also, properly frozen, can be held in prime condition for a year or longer. Poultry loses in palatability, but if hard frozen it may show fairly good quality up to ten or twelve months. Held at higher temperatures, eges may be kept for nine months or so, and potatoes for six. Fruits, on the other hand, owe so much of their desirability to volatile flavors that they are not generally suitable for longer holding than is nece ary for their distribution. Some apples and pears improve for a while, becoming appreciably sweeter, but it is another story with most of the others—strawberries and peaches, for ex: ample, rapidly losing their merit. The most important ice-making and refrigerating methods of present use are the Compre ion and Absorption, the former being that chiefly employed. In the Compre ion system, anhydrous ammonia (ammonia gas) is condensed by pre ure and then reduced to a liquid by chilling in a cooled ‘‘coil’’ of pipes. The liquid is released into another coil, known as the ‘‘expansion pipes.’’ This step effects refrigeration, for the liquid re-evaporates in them—and the reforming gas absorbs the (comparative) heat of the surroundings—converting water into ice, or reducing the temperature in cooling-rooms, or being otherwise variously utilized. The expanded gas goes back to the compre or to be continuously used over and over again,. By the Absorption method, a water solution of ammonia is similarly employed as the fundamental agent. The use of the expansion pipes (of either method) may be either direct as noted; above (by close or complete contact with the water or atmosphere to be frozen or chilled), or indirect by their action on strong brine or on air-coils, these then to be emploved as the immediate agents. The brine may be made with common salt, but is preferably of calcium chloride. Artificial Ice. The principal forins of manufactured ice—and the only styles of commercial distribution—are Can and Plate. Can ice is obtained by setting cans of water in brine-tanks refrigerated by expansion pipes. It is generally good in quality but has a tendency to be soft in the center. The water is carefully purified before running into the cans, as any foreign matter present is forced to the center during the freezing and will show as a core in the upper center of the block. Also to be avoided is an exce of air t bubbles, which will render it porous. Plate ice is made in oblong tanks in which the water is agitated by air-jets - J to remove the air particles and a ist the freezing action to drive the impurities to the center, which remains uncon-: | gealed and is Jater run off. The sides of the tanks consist of iron plates set on Marking ice for eutting both sides of expansion coils. The ice forms on these plates—hence its name. As removed from the tanks, it is obtained in blocks, generally about twenty: - feet long, ten feet wide, and one foot thick, weighing six to seven tons. Artificial ice was formerly soft and _ —— sa consequently of poor keeping quality, but the present standard product is both hard and lasting. a _ Natural Ice varies with conditions of J: ° ' water and weather, from opaque and { j. | somewhat soft from the air enclosed to | an excellent crop, clear and hard. Sawing ice In bygone days, before the advent of refrigerating machinery, natural ice was of importance in international commerce. During the first part of the ee nineteenth century, ice from Wenham; a Lake (twenty miles or so north of Bos- ‘ | ton) was shipped all over the world—to \ | South America, to England, to India.: Big ice-houses in Liverpool and London |~ 77 === — _ oF annually received and distributed tons. = a alll 7 \. - Impure Ice. It is incumbent upon mu- ——.; “ nicipalities and individuals to protect [#37 - themselves against the sale of ice, whether natural or artificial, produced —. from contaminated water. Under cer- —s tain conditions it may prove actively ‘Floating in?’ the cut ice unwholesome. The increase in population and the growth of manufacturing industries has so extended the pollution of lakes and rivers, that in the larger towns and cities the consumption of local natural ice is often fraught with considerable danger. The use of artificial ice from water which has undergone thorough preliminary purification is then the only safe recourse, unle ice from unpolluted sources can be profitably imported. Refrigerators. ‘The refrigerator of the ordinary household, of small commercial establishments, and of ice-charged railway-cars, ete., operates by the facilities given for the circulation of air alternately chilled (and falling) from contact with the ice, and warmed (and rising) from the higher temperature of the storage-chambers, From 36° to 38° Fahr. is the lowest obtainable from ice alone, but a freezing temperature may be secured by mixing salt with it. Good insulation in the construction of refrigerators and cooling-rooms is e ential for economy and efficiency. Also, an ice-chamber kept filled is, in the long run, more economical than the ice-chamber that is nearly empty much of the time.