236 NON-METALS AND THEIR COMBINATIONS. 



With the exception of hydrochloric acid, which has been considered, 

 none of the five acids is of practical interest as such, but many of 

 the salts of hypochlorous and chloric acids, known as hypochlorites 

 and chlorates respectively, are of great and general importance. 



The constitution of the chlorine acids may be represented by the following 

 graphic formulas. It is here assumed that chlorine is univalent in hypochlo- 

 rous, trivalent in chlorous, quinquivalent in chloric, and septivalent in per- 

 chloric acid : 



II II 



H O Cl, H O Cl = 0, H O Cl, H O Cl = O 



O O 



Chlorine monoxide, C1 2 O, and Hypochlorous acid, HC1O. When 

 chlorine is passed over yellow mercuric oxide in a tube, chlorine mon- 

 oxide is formed, thus, 



2HgO + 2C1 2 = HgO.HgCL, + C1 2 O. 



It is a brownish-yellow gas which decomposes with explosion when 

 heated. One volume of water dissolves 200 volumes of the gas, 

 giving a yellow solution of hypochlorous acid which has the strong 

 odor of the chlorine monoxide, 



C1 2 O + H 2 O = 2HC1O. 



Hypochlorous acid is also obtained in solution when chlorine gas is 

 passed into a suspension of mercuric oxide in water, thus, 



2HgO + 2C1 2 + H 2 = HgO.HgCl, -f 2HC1O. 



The compound known as mercury oxychloride is formed and may be 

 removed, being insoluble. 



Properties. Hypochlorous acid is a feeble (slightly ionizing) mono- 

 basic acid, which unites with active bases, forming hypochlorites. It 

 can be obtained only in solution, and keeps only when dilute and 

 cold. When concentrated it changes gradually to a considerable ex- 

 tent into chloric and hydrochloric acids, thus, 

 3HC10 = HC10 3 + 2HC1. 



Warming a solution of the acid, or exposing it to sunlight, causes a 

 rapid evolution of oxygen, 



2HC10 = 2HC1 + 2O. 



As a result of this action, the acid is a strong oxidizer. This decom- 

 position is interesting, as it explains the oxidizing action of chlorine 

 in the presence of water, and the fact that chlorine water exposed to 

 bright light does not keep, but gives off oxygen and leaves a solution 

 of nothing but hydrochloric acid. When chlorine is dissolved, a re- 

 versible reaction takes place, thus, 



C1 2 + H 2 ^ HC1 + HC10. 



