CHAPTER XI 



MURIATIC ACID AND CHLORINE 



A. THE DISCOVERY OF CHLORINE 



Scheele's investigation of pyrolusite (1771-1774). 

 During the years from 1771 to 1774 Scheele was occupied, 

 at the request of Bergman, in the investigation of a Swedish 

 mineral to which the name of " Brunsten " or " Manganese" l 

 was given. This mineral is now generally known as 

 PYROLUSITE, whilst the name MANGANESE has been trans- 

 ferred to the metal which it contains. This mineral was a 

 black powder which resembled the metallic calces in appear- 

 ance, but differed from them in being insoluble in dilute 

 oil of vitriol and in nitric acid ; it dissolved, however, in 

 presence of various inflammable substances, such as sugar 

 and gum, and had the curious quality of dissolving in the 

 weak acids (sulphurous and nitrous acids) which are pro- 

 duced by reducing or " phlogisticating " oil of vitriol and 

 nitric acid. The mineral could also be rendered soluble by 

 baking it with oil of vitriol, when a gas was given off identi- 

 cal in its properties with the "fire air," or oxygen, which 

 Scheele had prepared by heating nitre. 



Pyrolusite was thus shown to have the properties of a calx 

 combined with oxygen. Such compounds of a calx with 



1 "On Manganese, Manganesium, or Magnesia Vitrariorum," 

 Scheele's Essays, tr. 1786, repr. 1901, pp. 52-104. 



