534 MANUAL OF MILK PRODUCTS 



freezer. There are several other substances which could be used 

 in place of common salt to produce this same effect, as for ex- 

 ample calcium chlorid and ammonium chlorid ; but these pos- 

 sess several natural disadvantages, not to speak of their greater 

 cost, which preclude their general use. 



Salt and ice 



A fine salt dissolves much more rapidly than does a coarse 

 salt, and as a result cold is more quickly produced. Its use is 

 not common, however, for the reason that it is usually too high 

 priced, and further that it tends to form crusts and bridges which 

 prevent the ice from settling and fitting around the freezer. 

 Coarse barrel salt, such as is ordinarily used for stock purposes, is 

 satisfactory when used with caution, especially with small brine 

 freezers, and it is considerably cheaper than the crushed rock 

 or the ordinary flake ice cream salt. The pulverized rock salt, 

 however, is decidedly to be preferred for packing purposes 

 despite its higher cost, for it rattles more thoroughly through 

 the crevices of ice, and does not melt so rapidly and thereby con- 

 tinues the cold for a longer time. 



The ice should be broken quite fine, thus allowing more 

 surface exposure for the action of the salt and causing more 

 rapid freezing. Coarse lumps frequently cause trouble by 

 cramping against the freezing can. Where it is difficult or im- 

 possible to break the ice fine, it will be found especially con- 

 venient to pour water around the freezer at the start. This 

 tends to float the lumps and to prevent the grinding and snub- 

 bing so often noticed, especially with hand freezers. Ice that has 

 once been used for freezing may well be used for packing pur- 

 poses, but, having lost its many sharp points and edges and at 

 times too its "specific cold," it is not as well adapted to freezing 

 purposes as is fresh ice. White ice, i.e. snow ice, because of 

 the larger amount of air which it contains, melts more slowly 



