THE SALTING OF FISH. 



25 



chloride as impurity is sufficient to produce a very stiff, hard fish. 

 One per cent of calcium chloride produced a softer fish, but yet one 

 which was much harder than that produced by pure sodium chloride. 

 Four and seven-tenths per cent of magnesium chloride, as impurity, 

 produced a fairly hard, stiff fish, with a very bright, shiny appear- 

 ance. . ... 



Both calcium chloride and magnesium chloride, as impurities in 

 salt, caused a very noticeable whitening. This whitening could easily 



6 



9 



10 



Fig 1. — Curves show retardation of penetration of salt due to 1 per cent of calcium 

 chloride impurity (section I to 1 cm. depth). Figures at left indicate per cent of 

 chlorine in di-y fish ; at bottom, time in days. 



be followed, as it was first observed in the outer portions of the fish 

 and moved toward the center until at the end of from 10 to 13 days 

 the fish was uniformly white throughout. Calcium chloride was 

 most active in this regard. 



Figures 1 to 4 illustrate graphically the data presented in the 

 tables. In each case the time in days is plotted along the ordinate 

 (horizontal line). The percentage of chlorine in the dry fish is 

 plotted along the abscissa (vertical line). 



Figure 1 shows how the percentage of chlorine in fish (the amount 

 of sodium chloride contained in the fish) increases for 10 days. The 



