Ice
From Encyclopediak
Ice, water frozen into a solid state. Under ordinary conditions pure water becomes solid at 32 F. Impurities. such as salt in solution and increase of pressure upon the surface, tend to lower the freezing point. Sea water freezes at a lower temperature than fresh, water. When water freezes, most of the salts held in solution are separated from it. Hence pure water can be obtained from sea water by freezing. When water freezes, it expands hence ice is lighter than water. This expansive force is so great that it is practically irresistible. Not only all glass and earthen vessels burst when water in them freezes, but iron vessels seem to offer no better resistance, and even rocks are rent asunder by this force, many of the huge rocks lying at the foot of cliffs being broken off by water freezing at first in small cracks, then in the larger cracks formed each succeeding season.
ICE HARVESTING. Natural ice from the lakes, streams and rivers of cold regions is harvested in winter. The fin-it step is to clean off the snow and trash by means of a sort of a scraper after this the field is run over by a marker drawn by a horse, which cuts parallel grooves in the ice about three feet apart then another set of grooves is run across the ice field at right angles to the first and about the same distance apart. The ice is cut into cakes by a special form of plow, consisting of a steel bar, to which is attached a set of knives, one behind the other. The plow cuts into the ice only a few inches. When the plowing is finished, the first cake is cut out by a saw the others are then split off by striking a wedge-shaped steel bar into the cuts made by the plow. The cakes are finally floated to the foot of an elevator, which takes them to the desired story of the ice house, where they are packed in sawdust until needed. On the Hudson River, in Maine and on the lakes and streams of Wisconsin and Michigan, particularly near Chicago, many ice houses of great magnitude are erected. Some of these buildings are nearly 300 ft. long and five stories high, and are equipped with galleries running the entire length of the building, which are lowered or hoisted, as may be desired, to each of these stories for loading the ice. Special devices are used for loading cars from the ice house, and a steam power plant furnishes the power.
MANUFACTURE OF ICE. In localities removed from natural ice production, it is often cheaper to make ice by artificial means than to transport it. There are several types of apparatus for maleing ice, all depending for success upon the principle that cold is produced by the expansion of compressed air, gas or a liquefied vapor like ammonia. The most commonly used machines are those in which anhydrous, or waterless, ammonia is employed, and in which there is an evaporator or congealer by which the ammonia is vaporized. This vapor is th.en compressed by a pump or air compressor, and when it is allowed to expand in coils of pipe, produces intense cold. The process is made continuous and the liquid ammonia is used over and over. Cans of distilled water are placed in a tank of this liquid, which freezes the contents of the can into a block of ice. As this ice is free from all impurities, it is much preferred to natural ice. Recent improvements in the art have been productive of very low-priced plants on such scale as to allow hotels, hospitals, asylums, etc., to install them and make their own ice and have means for cold storage. See COLD STORAGE.
