ALKALINE AND HEAVY METALS. 395 



Chloride of Lime is a white powder smelling of chlorine, and is produced 

 by passing the gas over the hydrate of lime spread on trays for the purpose. 

 It is the well-known " bleaching powder." It is also used as a disinfectant. 

 The Fluoride of Calcium is Derbyshire spar, or " Blue John." Fluor spar is 

 generally of a purple hue. We may add that hard water can be softened 

 by adding a little powdered lime to it. 



MAGNESIUM sometimes finds a place with the other metals, for it bears 

 a resemblance to zinc. Magnesium may be prepared by heating its chloride 

 with sodium. Salt is formed, and the metal is procured. It burns very 

 brightly, and forms an oxide of magnesia (MgO). Magnesium appears in the 

 formation of mountains occasionally. It is ductile and malleable, and may 

 be easily melted. 



Carbonate of Magnesia, combining with carbonate of lime, form the 

 Dolomite Hills. When pure, the carbonate is a light powder, and when 

 the carbonic acid is taken from it by burning it is called Calcined Magnesia. 



The Sulphate of Magnesia occurs in sea-water, and in saline springs 

 such as Epsom. It is called " Epsom Salts." Magnesium wire burns brightly, 

 and may be used as an illuminating agent for final scenes in private 

 theatricals. Magnesitc will be mentioned among Minerals. 



STRONTIUM is a rare metal, and is particularly useful in the com- 

 position of "red fire." There are the carbonate and sulphate of strontium ; 

 the latter is known as Celestine. The red fire above referred to can be made 

 as follows, in a dry mixture. Ten parts nitrate of strontia, I \ parts cholorate 

 of potassium, 3^ parts of sulphur, I part sulphide of antimony, and \ part 

 charcoal. Mix well without moisture, enclose in touch paper, and burn. 

 A gorgeous crimson fire will result. 



METALS OF THE EARTHS. 



ALUMINIUM (Aluminum) is like gold in appearance when in alloy with 

 copper, and can be procured from its chloride by decomposition with 

 electricity. It occurs largely in nature in composition with clays and 

 slates. Its oxide, alumina (A1 2 O 3 ), composes a number of minerals, and 

 accordingly forms a great mass of the earth. Alumina is present in various 

 forms (see Minerals) in the earth, all of which will be mentioned under 

 Crystallography and Mineralogy. The other nine metals in this class do 

 not call for special notice. 



HEAVY METALS 



IRON, which is the most valuable of all our metals, may fitly head our list. 

 So many useful articles are made of it, that without consideration any one 

 can name twenty. The arts of peace and the glories of war are all 

 produced with the assistance of iron, and its occurrence with coal has 



