218 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



CHLORIDE and its solution in water as HYDROCHLORIC ACID/ 

 the muriates derived from the acid being described as 



CHLORIDES. 1 



B. CHLORINE AN ELEMENT. 



Gay-Lussac and Thenard regard chlorine as the oxide 

 of an imaginary radical. The French chemists were so 

 obsessed with the idea that all acids must contain oxygen, 

 that they refused to abandon this view, even when chlorine 

 had been proved to be a simpler substance than muriatic 

 acid. Thus, instead of admitting that chlorine might be an 

 element, they regarded it as the oxide of an unknown 

 radical, analogous with nitrogen, carbon, sulphur, or phos- 

 phorus. Muriatic acid, formed by the union of chlorine 

 with hydrogen, was regarded as a ternary compound of this 

 radical with hydrogen and oxygen, or perhaps with water. 

 According to this new view : 



Chlorine = X + oxygen. 

 Muriatic acid = chlorine + hydrogen 



= X -f oxygen + hydrogen. 



It will be seen that this theory merely substituted for 

 chlorine the symbol (X + oxygen), where X was an imaginary 

 radical which had never been isolated. To prove the 

 correctness of their theory, it was necessary for Gay- 

 Lussac and Thenard to extract oxygen from chlorine, or 

 water from muriatic acid, without making use of substances 

 in which oxygen was already present. The experiment of 

 passing muriatic gas over litharge was obviously invalid (as 

 Davy pointed out in 1810), since the formation of water 



1 The name "hydrochloric acid "was proposed by Gay-Lussac in 

 1814 (Ann. d. Chimie, 1814, 91, 9). The term " chloride "'was intro- 

 duced by Davy in 1816 {Works, V. 516), as a substitute for the 

 word " chlorure " suggested by Gay-Lussac. 



