22 THE SALTING OF FISH. 



An attempt was, therefore, made to measure the rate of penetra- 

 tion of pure salt into fish as compared with the rate of penetration 

 of mixtures of sodium chloride with the common impurities in salt; 

 that is calcium, magnesium, and sulphate. 



It was fortunate that the writer began his experiments on the 

 rate of penetration of salt with chemi(?ally pure sodium chloride, for 

 this led to the discovery that the impurities in salt were largely re- 

 sponsible for the physical characteristics of the salted fish. The 

 fish chosen for this work was the squeteague or weakfish {Cynoscion 

 regalis)^ which could be obtained in a nearly fresh condition almost 

 all the year around in Baltimore, where the experimenter was work- 

 ing. This fish is of medium fatness and was obtained on the market 

 in quantity at any desired uniform size. It had been planned to 

 try any improvement that might be worked out on the alewife or 

 river herring. The squeteague was more similar to the river herring 

 than any other fish that could be purchased throughout a long 

 season. 



After considering many possible methods of determining the rate 

 of penetration of salt into fish it was decided to determine the per 

 cent of chlorine in different sections of the fish from day to day. 

 The layer from one half to 1 cm, in depth was found by experience 

 to give the most uniform results. 



Thus far the work has been applied to but one fish, the squeteague. 

 The writer does not claim that the results of the work on this one fish 

 can be applied without change to all varieties of fish. Different 

 results might be obtained if a fat fish, such as the mackerel, had 

 been used. Clark and Almy (1918) give the fat content of a com- 

 posite sample of weakfish, on May 1, as 2.34 per cent (fresh basis) ; 

 on September 25 a similar composite sample contained 0.52 per cent. 

 However, they observed also that different squeteague in the same 

 school and various schools differ greatly in their fat content. 



Fish in good condition and of as nearly uniform size as possible 

 were obtained from wholesale fish dealers of Baltimore, After cut- 

 ting the length of the belly, eviscerating, and removing the heads, 

 they were salted with dry salt of known composition. The salt used 

 was Baker's analyzed, chemically pure sodium chloride," or mix- 

 tures of this with other salts of the same grain size. This salt was 

 just a little smaller grained than ground alum, or packer's salt, 

 which is so widely used in the fish-salting industry. The salts were 

 thoroughly mixed, so that all portions were of uniform composi- 

 tion. The fish were rolled in salt, and salt was sprinkled over each 

 layer of fish, as is the practice of the trade. For every three parts, by 

 weight, one part of salt was added when first salted. 



After the fish had been in salt 24 hours one part, by weight, of 

 salt was added for every 15 parts of fish. Later, at the end of six 

 days, 1 part, by weight, of salt was added for every 30 parts of 

 fish. The fish were placed belly down in 2-gallon stone jars. The 

 above procedure was carried out in order to duplicate, if possible, 

 the method of salting fish in use at Gloucester. 



In the different experiments the temperature of salting was kept 

 as near 68° F. as possible by surrounding the jars with running 



