282 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



redness." "When exposed to air, it rapidly tarnished, 

 and fell into a white powder, which was barytes. When 

 this process was conducted in a small portion of air, the 

 oxygen was found absorbed, and the nitrogen unaltered; 

 when a portion of it was introduced into water, it acted 

 upon it with great violence and sunk to the bottom, pro- 

 ducing in it barytes ; and hydrogen was generated" (A.C.R. 

 VI. 49)- 



Strontium was described by Davy as closely resembling 

 barium. 



In reference to calcium, Davy writes : 



" The metal from lime, I have never been able to examine 

 exposed to air or under naphtha. In the case in which I 

 was able to distil the quicksilver from it to the greatest 

 extent, the tube unfortunately broke, whilst warm, and at 

 the moment that the air entered, the metal, which had the 

 colour and lustre of silver, instantly took fire, and burnt 

 with an intense white light into quicklime" (A.C.R. 

 VI. 50). 



The metal is now manufactured on a considerable scale 

 by passing an electric current through the muriate, CALCIUM 

 CHLORIDE, to which fluor-spar (CALCIUM FLUORIDE) is added 

 to render it more easily fusible. 



" The metal from magnesia seemed to act upon the glass, 

 even before the whole of the quicksilver was distilled from 

 it. In an experiment in which I stopped the process before 

 the mercury was entirely driven off, it appeared as a solid, 

 having the same whiteness and lustre as the other metals of 

 the earths. It sunk rapidly in water, though surrounded 

 by globules of gas, producing magnesia, and quickly 

 changed in air, becoming covered with a white crust, and 

 falling into a fine powder, which proved to be magnesia" 

 (A.C.R. VI. 50). 



Composition of the earths. Having isolated metals 

 from the four alkaline earths, Davy was able to prove by 



