COMMON SALT: HYDROCHLORIC ACID 8i 



given below? Now transfer the neutral liquids to weighed 

 porcelain dishes, evaporate on the water bath to dryness, 

 and weigh. Is the weight of salt obtained less than the 

 weight of caustic soda and hydrochloric acid used by the 

 weight of water that would be set free according to the 

 equation — 



NaOH + HCl = NaCl + HgO ? 



The existence of acids, which are compounds of non- 

 metallic elements with hydrogen, as well as those which are 

 compounds of acidic oxides with water, and which may be 

 distinguished as oxy-acids, makes it necessary to extend the 

 meaning of the term "acid" to compounds containing 

 hydrogen that is replaceable by metals with the formation of 

 salts. The term salt, too, must not be restricted to com- 

 pounds of basic and acidic oxides, but includes compounds 

 which, formed by the action of bases on acids with liberation 

 of water, are compounds of metals and non-metals. 



Metallic chlorides occur very abundantly in nature. Enormous deposits 

 of rock-salt, i.e. chloride of sodium, usually mixed with a little chloride of 

 magnesium, which renders it deliquescent, and sulphate of calcium, are 

 found in many parts of the world. In England the principal deposits are 

 in Cheshire, where the salt is obtained by mining or by evaporating the 

 brine pumped from shafts sunk into the salt. In the North Sea the water 

 contains about 2. 7 per cent, of sodium chloride and o. 5 per cent, of other 

 chlorides and sulphates, while in the Atlantic Ocean the water contains 

 about 3.3 per cent, of sodium chloride, and 0.3 per cent, of the other salts. 

 At Stassfurt, in Germany, there exist large deposits of "carnallite," 

 KCl.MgCla; 6H2O, from which the so-called "muriate of potash" 

 (chloride of potassium), used as an artificial manure, can be obtained by 

 simply dissolving the salt in water and evaporating till crystallisation com- 

 mences, the magnesium chloride and part of the potassium chloride being 

 left in solution. In the same deposits the "kainite," K2S04.MgS04. 

 MgCl2 ; 6H2O, is found, which is also so largely used as a manure. 

 Small quantities of bromides and iodides, the corresponding salts of 

 bromine and iodine, two elements of properties analogous to chlorine, are 

 frequently found associated with chlorides. 

 6 



