GENERAL REMARKS ON THE KETTLE PROCESS 57 



low in the pickle will cause a decomposition of the mag- 

 nesium chloride into magnesium oxide and hydrochloric 

 acid, the latter readily attacks the iron forming ferrous chlo- 

 ride, the slightest trace of which when present in the salt 

 will cause a decided discoloration of the latter at the time 

 the salt becomes ready for the market. 



The grain of the salt, namely the size of the crystals, de- 

 pends on the temperature at which the salt is made, and 

 consequently on the quickness or slowness of the evapora- 

 tion. The separation of the salt or its crystallization in a 

 heated brine begins at the moment when the latter has 

 reached its point of saturation. This crystallization always 

 takes place on the surface of the brine and never at the 

 bottom, since there the temperature is highest, and salt is 

 more soluble in the hotter brine. The little cubes will in- 

 crease in size as long as they remain on the surface of the 

 brine but not when they have once sunk to the bottom of 

 the heated liquid. Hence, to produce a coarse salt, the 

 brine must remain as much as possible undisturbed in order 

 to allow the crystals to grow, which is impossible in a very 

 hot brine. 



The salt made by the ordinary kettle method is not of a 

 uniform grain or crystal, since the front kettles, which usually 

 boil very rapidly yield a heavy salt of which the crystals are 

 small, hard and sharp to the touch, while the back kettles 

 produce a very light, flaky and coarse grained salt very soft 

 to the touch. By mixing both a good grained average salt 

 is obtained, which is known in the market as "common fine 

 salt." 



The average composition of this is about as follows : 



Sulphate of lime (calcium sulphate) 1 . 30 per cent. 



Calcium chloride 0.16 



Magnesium chloride °- *5 



Sodium chloride salt 95-49 



Moisture 2 -9° 



Since the year 1862 there has been produced at Syracuse 

 a salt of very superior quality for the dairy and table, the 

 8 



