238 



METALS. 



Magnesium- 589 ' MAGNESIUM. Magnesium is a Soft 



description, white metal, prepared from its chloride 



preparation, , . . 



solvents and instead oi the oxide, by similar means. 

 None of the metals of this class have as yet 

 been applied to any useful purpose in the arts. Water 

 oxidizes magnesium as it does the other metals of the 

 class, but converts it into an insoluble white powder. 

 Most acids dissolve it. 



CLASS III. 



ALUMINIUM 



590. DESCRIPTION. Aluminium is a 

 bluish white metal, made from common 

 currence, and c j a y. It is about one-third as heavy as 



solvents ? * y 



iron. It fuses at the same temperature 

 as silver, and preserves an untarnished surface in the 

 air. It does not decompose water, even with the aid 

 of boiling heat. Alloyed with iron, it protects the 

 latter from the action of the air. This metal is a con- 

 stituent of common clay, and therefore a part of all fer- 

 tile soils and the rocks that produce them. It is also 

 a constituent of numerous minerals. By its discovery 

 every clay bank is converted into a mine of precious 

 metal. 



How is it pre- 591. PREPARATION. Aluminium is pre- 

 pared? pared like magnesium, from its chloride, 

 by fusion with potassium or sodium. The latter rnetal 

 is commonly employed. The fluoride may also be 

 used in the process, or the mineral cryolite, which 



