xi MURIATIC ACID AND CHLORINE 231 



B. CHLORINE AN ELEMENT. 



Davy, in 1810, being quite unable to separate oxygen from 

 chlorine, suggested that the gas was an element and gave to it 

 the name chlorine. He determined the volumetric composition of 

 hydrogen chloride, which is formed without change of volume 

 when chlorine acts upon hydrogen or upon sulphuretted 

 hydrogen. 



H 2 + C1 2 -> 2HC1 



I -VOl. I Vol. 



H 2 S + C1 2 -> 2HC1 + S 



i vol. i vol. 2 vols. solid. 



He showed that half its volume of hydrogen is liberated when 

 the hydrogen chloride is acted on by metals, thus : 



-. Tin Sn + 2HC1 -> SnCl 2 + H 2 . 



2 vols. (Stannous i vol. 



chloride.) 



Zinc Zn + 2HC1 -> ZnCl 2 + H 2 . 



2 vols. (Zinc chloride.) i vol. 



Potassium 2K + 2HC1 -> 2KC1 + H 2 . 



2 vols. (Potassium i vol. 



chloride.) 



Mercury 2Hg+ 2HC1 -> Hg 2 Cl 2 + H 2 . 



(By sparking.) 2 vols. (Calomel.) i vol. 



It should be noted that the stannous chloride, SnCl 2 , 

 prepared in this way contains less chlorine than the stannic 

 chloride, SnCl 4 , prepared by the action of chlorine on tin and 

 that calomel or mercurous chloride, Hg 2 Cl 2 , contains a smaller 

 proportion of chlorine than the corrosive sublimate or mercuric 

 chloride, HgCl 2 , prepared by the action of chlorine on mercury 

 or its sulphide. In the case of zinc and potassium the products 

 are identical with those obtained by the action of chlorine on 

 the metal. 



All these chlorides are binary compounds of metal and 

 chlorine analogous with the sulphides and oxides, rather than 

 with ternary salts such as the sulphates and carbonates. This 



