xin THE DECOMPOSITION OF THE ALKALIS 281 



recognised and had indeed led Lavoisier to suggest that 

 they were of the same nature ( Works, I. 122, 126, 137). 



Fresh from his recent successes with potash and soda, 

 Davy, in 1808, attacked the alkaline earths, and after some 

 failures isolated their metals in the form of amalgams with 

 mercury. 



" The earths were slightly moistened, and mixed with one- 

 third of red oxide of mercury, the mixture was placed on a 

 plate of platina, a cavity was made in the upper part of it to 

 receive a globule of mercury, of from fifty to sixty grains in 

 weight, the whole was covered by a film of naphtha, and the 

 plate was made positive, and the mercury negative, by a 

 proper communication with the battery." 



"The amalgams obtained in this way, were distilled 

 in tubes of plate glass, or in some cases in tubes of common 

 glass. These tubes were bent in the middle, and the 

 extremities were enlarged, and rendered globular by blowing, 

 so as to serve the purposes of a retort and receiver." 



" The tube after the amalgam had been introduced, was 

 filled with naphtha, which was afterwards expelled by boiling, 

 through a small orifice in the end corresponding to the 

 receiver, which was hermetically sealed when the tube 

 contained nothing but the vapour of naphtha, and the 

 amalgam." 



" I found immediately that the mercury rose pure by 

 distillation from the amalgam, and it was very easy to 

 separate a part of it; but to obtain a complete decom- 

 position was very difficult" (A.C.R. VI. 46 47). 



In this manner Davy obtained metals from baryta, from 

 lime, and from the earth now known as strontia j these 

 metals he named BARIUM, CALCIUM, and STRONTIUM. He 

 seems also to have obtained a specimen of the metal con- 

 tained in magnesia ; he first called this metal " magnium," 

 but afterwards reverted to the name MAGNESIUM. 



Properties of the metals of the earths. Barium was 

 described by Davy as " a white metal of the colour of silver," 

 solid at ordinary temperatures but " fluid at a heat below 



