140 CHLORIDES OF CALCIUM AND MAGNESIUM. 



thrown into the fire ; and dissolves in less than 3 times (2.85 

 times) its weight of water at 60 F., and in less than twice its 

 weight of boiling water. When dissolved in four times its 

 weight of water, it lowers the temperature of the water 

 by 201 F. 



This chloride exists in small quantity in sea water and in 

 salt springs. That which is met with in commerce is for the 

 most part obtained from kelp, and is employed in the manu- 

 facture of alum. 



2. Chloride of sodium, or common salt, is a white saline 

 substance, which crystallises in cubes, is without smell, has an 

 agreeable saline taste, and crackles or decrepitates when thrown 

 into the fire. In these respects it agrees with the chloride of 

 potassium ; but it differs from it in the following pro- 

 perties : 



a In its ordinary or commercial form, it becomes moist in a 

 damp atmosphere more readily than chloride of potassium. 



b It dissolves in less than three times (2.78 times) its weight 

 of water at 60 F., but boiling water does not sensibly dissolve 

 more of it than water at 60 does. 



c When dissolved in four times its weight of water, it only 

 lowers the temperature of the water 3^ (3.4) degrees, instead of 

 20J, the reduction produced by the chloride of potassium. 



3. Chloride of calcium is obtained by dissolving lime in 

 muriatic acid, and evaporating the solution to dryness. It is 

 colourless, and without smell, but has a disagreeable bitterish 

 taste. It attracts water from the air very rapidly, and runs to 

 a liquid, or deliquesces. It is also exceedingly soluble in cold 

 water. It occurs as a refuse in several manufacturing pro- 

 cesses. 



4. Chloride of magnesium is obtained by dissolving magnesia 

 in muriatic acid, and evaporating the solution to dryness ; but 

 it exists largely in the mother liquor of the salt pans, and from 

 that cheap source it is usually obtained for manufacturing and 

 other purposes. It is a white substance, void of smell, but has 

 a disagreeable bitter taste. It is also very deliquescent, and 

 very soluble in water. In all these respects it has much resem- 

 blance to the chloride of calcium. 



