62 THE ELEMENTS OF PLANT FOOD 



containing this element. In the presence of moisture 

 it breaks up and destroys the molecules of coloring 

 matter of dye stuffs, thus acting as an effective bleach- 

 ing agent. This is due to the action of O which is set 

 free from water by Cl. 



In direct sunlight Cl decomposes water according to 

 the following: 



2 H 2 O + 2 C1 2 == 4 HC1 + O 2 



Hydrochloric acid (HC1) is one of the most important 

 and one of the strongest acids known. The pure acid 

 is a gas. When absorbed by water, it makes the hydro- 

 chloric acid in the form that is used most frequently, 

 called muriatic acid. The acid is made by heating 

 common salt with sulphuric acid. 



Salt Sulphuric Sodium Hydrochloric 



acid sulphate acid 



2NaCl + H 2 SO 4 = Na 2 SO 4 + 2 HC1 



HC1 dissolves many metals and forms chlorides. 

 When it is mixed with nitric acid, 3 volumes of HC1 to 

 I volume of HNO 3 , it makes aqua regia (royal water), 

 which dissolves the " king of metals," gold. Plati- 

 num is also dissolved in a warm mixture of these acids. 

 HC1 is found in the human stomach and aids digestion. 

 It is used in the arts to a very great extent and is of 

 great value to the chemist. 



Bleaching Powder, chloride of lime. As usually 

 sold in cans, this is a mixed salt of hypochlorus and 

 hydrochloric acids. Cl may be easily set free by adding 

 a small quantity of acid or by exposure in the open 

 air, under which condition it will escape slowly. This 



