230 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



solutions he froze out chlorine hydrate, C1 2 + 8H 2 O. He found 

 that chlorine water was decomposed by light, liberating oxygen 

 and reproducing muriatic acid ; he therefore regarded chlorine 

 as a compound of oxygen with muriatic acid and called it 

 "oxymuriatic gas." The action is really a decomposition of 

 water by chlorine : 



the action is reversible, as shown by the double arrows, since 

 muriatic acid exposed to air and light becomes impregnated 

 with chlorine. 



Gay-Lussac and Thenard, in 1809, proved that muriatic gas 

 was a compound of hydrogen with chlorine, a fact that is 

 expressed by the modern name hydrogen chloride, HC1, for the 

 gas and hydrochloric acid for the solution. They separated the 

 hydrogen from it by the action of metals, thus : 



Potassium 2 K + 2 H Cl-> 2 KC1 + H 2 



(Potassium 

 chloride.) 



Iron Fe + 2HCl->FeCl 2 + H 2 



(Ferrous 

 chloride.) 



It should be noted that the ferrous chloride, FeCl 2 , produced in 

 this way contains less chlorine than the ferric chloride, FeCl 3 , 

 produced by the direct action of chlorine upon iron. 



Hydrogen, in the form of water, was also separated from 

 muriatic gas and litharge : 



2HC1 + PbO -> PbCl 2 + H 2 O 



(Hydrogen (Litharge.) (Lead (Water.) 

 chloride.) chloride.) 



They united hydrogen and chlorine to form hydrogen chloride : 

 (a) slowly by keeping in diffused daylight ; (b) rapidly by heat- 

 ing ; (c) with a violent explosion by exposure to bright sunlight. 

 Although they could not extract oxygen from chlorine even by 

 red-hot charcoal, they contended that chlorine gas was the oxide 

 of an unknown radicle and that muriatic gas was a ternary 

 compound of this radical with oxygen and hydrogen, thus : 



Chlorine = X + oxygen 



Muriatic gas = X + oxygen + hydrogen. 



