Collier's New Encyclopedia (1921)/Ice, Artificial
ICE, ARTIFICIAL, ice frozen by mechanical or chemical means. It has the great advantage of being easily rendered chemically pure, and it can be manufactured in the hottest countries. Its commercial value in the preservation and transportation of meats, fruits, etc., and for other purposes, can scarcely be estimated. The water is first boiled and allowed to settle. It is then distilled, boiled again and run through three kinds of filters. Underneath the great square middle space of the freezing room, which is paved with large rectangular removable tiles, is a series of tanks. These contain a strong solution of brine, and through it run scores of pipes which are charged with liquefied ammonia gas. When this volatile chemical leaves the engine room it is in the form of a fluid, but in making its long journey along the pipes which thread their way through the brine it evaporates into gas.
The evaporating process within absorbs so much heat from the surrounding mass of salt and water that the distilled water in the rectangular ice cans submerged in the brine is congealed into the finest ice. Each can contains 300 pounds of distilled water, which remains in its cold bath 48 hours. Natural gas is often employed in the process of manufacturing artificial ice. As it escapes from the borings with a pressure of 20 to 30 atmospheres, the lowering of the temperature as it is released serves to freeze water even in summer. A still more simple and inexpensive process of preparing artificial ice is used in connection with the newly-perfected method of condensing the atmosphere into a liquid. The rapid evaporation of liquid air absorbs an immense amount of heat and everything brought into contact with it is frozen.