REFRIGERATION OF FISH 



579 



affected. This was a difficulty, perhaps a fatal one, in the earlier 

 attempts at brine freezing made by Hesketh and Marcet, Rouart, 

 Rappleye, and Henderson. Ottesen discovered that if the proper 

 relations of concentration and temperature are observed penetra- 

 tion of salt may be reduced to a minimum, so much that it ceases to 

 be objectionable. 



Warm water will dissolve more salt than cold water. If we 

 saturate some warm water with salt and then cool the brine, some 

 salt will precipitate out as small crystals, leaving the brine weaker. 

 If we cool it more, some more salt crystallizes out and the brine is 

 still weaker. We can continue to cool it with separation of salt 

 until we get a temperature of 6.16° F. below zero, when the brine 

 will freeze solid. At this temperature the liquid portion contains 



35 



-*0 <4S 



SO 



-JO -s O -S 10 15 20 25 30 



Decrfes. Fahrehheit 



Fig. 29. — Temperature saturation curve of salt brine 



22.42 per cent salt. If Ave begin with a brine of such strength that 

 it is completely saturated with salt and immerse fish in it there will 

 be penetration. The upper part of the curve in Figure 29 represents 

 the concentration of the liquid portion, corresponding to the 

 temperatures. 



Now, if we begin with a very dilute solution of salt and cool it. 

 what happens? The temperature drops slightly below 32° F., with 

 no apparent change, because the salt has lowered the freezing point 

 of the water. A degree or two below 32° crystals appear, but they 

 are water ice and not salt. The separation of water in the form of 

 ice leaves the brine more concentrated, and its freezing point falls. 

 As we continue to extract heat more water separates out as ice and 

 the remaining brine becomes stronger and stronger, as indicated by 

 the lower part of the curve in Figure 29. When a temperature of 



