[HARRISON & KENNEDY] DISCOLOURATION OF CODFISH 



143 



die in salt stored from three to six months under semi-tropical con- 

 ditions. In any case, it would seem advisable for our importers to 

 insist on being furnished with old salt that has been stored for a period 

 of at least three months. 



Chemical Analyses of Salt. — Pure salt should contain only sodium 

 chloride, but all commercial salts contain a certain amount of im- 

 purities, sea salt, as a rule, a larger amount than mined salts. 



There is a difference of opinion among fishermen as to the best 

 salt for curing fish, but undoubtedly the majority of them favour 

 the use of sea salt, as they consider that fish cured with sea salt are 

 more evenly "struck," and that the fish are more moist and there is 

 no hard crust on the surface of the fish. The mined salts are usually 

 in finer crystals and when used the fish are more quickly "struck," 

 but the salt does not penetrate to the interior so well. It has been 

 suggested that the quick coagulation of the surface protein prevents 

 the penetration of the salt to the interior. 



Undoubtedly sea salt is more hygroscopic, and cured fish, if not 

 well dried, will often sweat or become very moist, due to the solar salt 

 taking up water from the atmosphere. Such substances as calcium 

 and magnesium chlorides, are very hygroscopic, and their presence 

 in ground salt produces caking when moisture is present. 



Analyses of Mined Salts. 



Moisture 



Calcium chloride 



Magnesium chloride. . 



Calcium sulphate 



Insoluble constituents. 

 Sodium chloride 



Insoluble 



Lime 



Magnesia 



Sulphuric anhydride. . 

 Sodium chloride 



Worcester, 

 U.S.A. 



0.2 



0.19 



0.09 



0.59 



0.01 



98.94 



Malagash 

 1.954 

 0.220 

 0.004 

 0.320 

 97.502 



Liverpool 



0.086 



0.515 



Traces 



0.252 

 98.961 



