THE SALTING OF PISH. 17 



METHODS OF MANUFACTURE. 



Domestic salt is prepared by one of tlie following processes : Steam 

 evaporation, vacuum evaporation, direct-heat evaporation, or solar 

 evaporation. 



Most of the salt produced in the eastern part of America, close to 

 the regions where fish are salted, is manufactured by steam evapora- 

 tion. The product produced hj this method, in jacketed kettles, 

 grainers, and vacuum pans, is a fine-grained salt. For some reason 

 there is much prejudice against the use of fine-grained salt for fish 

 salting. Because of this prejudice very little salt produced in this 

 way was used by fishermen previous to the war. During the war, 

 when the supply of coarse-grained salt was limited, a large propor- 

 tion of the fish salters began the use of fine-grained salt partially to 

 replace the coarse-grained salts. 



The salts produced by direct-heat evaporation are usually coarser 

 grained tlian those produced by steam evaporation. To-day this 

 jjrocess is seldom used except where it is possible to utilize waste 

 heat, and since such a small amount is prepared in this way, this 

 method of j)roduction is not considered an important factor in the 

 salt supply. 



Unfortunately for the fish trade, nearly all of the domestic solar 

 salt is produced in the arid regions of the West. The only place in 

 the East where this method of evaporation is practiced is in the 

 vicinity of Syracuse, N. Y. Because of the very high freight rates 

 eastward across the continent, the cost of the western solar salt on 

 the Atlantic coast is almost prohibitive. 



Pure salt is pure sodium chloride. There is no brand of commer- 

 cial salt on the market that is 100 per cent pure. There are, however, 

 salts on the market which are 99.95 per cent pure. Most of the 

 American salts are of greater purity than the foreign salts ; however, 

 there are a few British salts of great purity. The limited analytical 

 data available to the author indicate that British salts, with the ex- 

 ception of Turks Island are, on the whole, of much greater purity 

 than French, Spanish, and Italian salts. The reason for this prob- 

 ably is to be found in the method of manufacture. The southern 

 European salts are mainly solar salts, whereas the British salts, be- 

 cause of the climate, must be prepared in some other way. 



The ordinary procedure in the preparation of solar salts is to allow 

 sea water at high tide to run, or be pumped, into low-lying lands, 

 forming ponds. The outlet to the sea is then closed, and evaporation 

 is allowed to proceed. As the brine becomes more concentrated and 

 more nearly saturated it is run into other ponds. Finally, when the 

 saturation point has been reached the brine is run into crystallizing 

 ponds. Here the usual procedure is to allow evaporation to proceed 

 until the brine becomes high in magnesium chloride and low in 

 sodium chloride. Usually when a concentration of 32° B. is reached 

 the mother liquor is drained off and discarded. From the above 

 brief description of the process it will be seen that solar salt is likely 

 to be impure. Since sea water is high in calcium and magnesium 

 chlorides, it is likely that solar salt will be high in these constituents 

 if it is crystallized but once. 



