Ice-Salt Cooling

artificial refrigeration through the melting of a mixture of ice and certain salts. The temperature is lowered because of heat absorption as the ice melts and the salt dissolves. The composition of the cooling mixture is determined by the relationship between the temperature at which crystallization begins in a solution and the concentration of the solution (the solubility diagram). A mixture of small pieces of ice with common salt (NaCl) is usually used for ice-salt cooling; the melting point of a mixture with 22.4 percent NaCl (by weight in solution) is — 21.2°C.

A distinction is made between brine and air systems of ice-salt cooling. In brine cooling the brine produced in a refrigeration unit (an insulated container with an ice-salt mixture) is directed into the pipes of a cooling chamber and then into a tank, where it is cooled again by spraying the mixture. In the air system of ice-salt cooling, air that has been blown through a refrigerating unit is passed into the cooling chambers. Temperatures as low as — 15°C may be produced in the cooling chamber using this method. In addition to laboratory applications, ice-salt cooling is used in motor-vehicle and railroad transportation in the shipment of food products.