CHLORINE. 237 



Only a slight quantity of hypochlorous acid is formed at one time, 

 but its decomposition and constant removal in this way allows the 

 action to go forward to completion. The final result makes it appear 

 that chlorine decomposes water with direct liberation of oxygen, 

 which is usually represented by the equation, 



C1 2 + H 2 O = 2HC1 + O. 



Hypochlorites. For practical purposes solutions of free hypochlorous 

 acid are not made, but the acid is liberated from its salts when wanted. The 

 hypochlorites are formed by the action of chlorine on the hydroxide of potas- 

 sium, sodium, calcium, etc., at the ordinary temperature. As stated above, 

 chlorine with water forms HC1 and HC1O, but the action does not go far, 

 because these two acids tend to decompose each other in the reverse direction 

 to produce chlorine. But if they are removed, as by neutralization, action 

 will be complete, thus, 



2C1 -f H 2 O = HC1 + HC1O 



HC1 + NaOH = NaCl + H 2 O 



HC10 + NaOH = NaCIO + H 2 O. 



It will be seen that when hypochlorite is made in this manner there is always 

 an equivalent amount of a chloride in the mixture. The reaction is generally 

 written, 



2C1 + 2NaOH = NaCl + NaCIO + H 2 O. 



When a hypochlorite is acidified with an active acid, the reverse of the above 

 reactions takes place, hydrochloric and hypochlorous acids being liberated, 

 which between them evolve chlorine (see bleaching powder). When a hypo- 

 chlorite is heated, it decomposes into chlorate and chloride, thus, 



SNaCIO = NaClO s + 2NaCl. 



Under some conditions a hypochlorite slowly gives off oxygen, leaving a chlo- 

 ride, but the action may be enormously increased by adding a catalytic agent, 

 for example, a cobalt salt (see under Oxygen). 



Solution of chlorinated soda, Liquor sodae chlorinatse (Solution of 

 sodium hypochlorite, Labarraque 's solution). This is a solution that yields 2.4 

 per cent, of available chlorine. It contains chloride and hypochlorite of sodium, 

 and is made by adding sodium carbonate to a solution of bleaching powder 

 (calcium hypochlorite), thus precipitating calcium carbonate : 



CaCl 2 -f Ca(ClO) 2 -f 2Na 2 CO 3 = 2CaCO 3 -f 2NaCl + 2NaClO. 



It is a clear pale greenish liquid, having a faint chlorine-like odor and strong 

 bleaching properties. 



Chloric acid, HC1O 3 , may be obtained from potassium chlorate b}* 

 the action of hydrofluosilicic acid ; it is, however, an unstable sub- 

 stance which will decompose, frequently with a violent explosion. 

 Chlorates are generally obtained by the action of chlorine on alkali 

 hydroxides at a temperature of about 100 C. (212 F.). 

 6KOH + 6C1 as 5KC1 + KC10 3 + 3H 2 O. 



