ALKALINE METALS. 



393 



Sulphate of Soda is "Glauber's Salt"; it is also employed in glass-making. 

 Mixed with sulphuric acid and water, it forms a freezing mixture. Glass, 

 as we have seen, is made with silicic acid (sand), soda, potassa, oxide of 

 lead, and lime, and is an artificial silicate of soda. 



LITHIUM is the lightest of metals, and 

 forms the link between alkaline and the alka- 

 line earth metals. The salts are found in many 

 places in solution. The chloride when decom- 

 posed by electricity yields the metal. 



CESIUM and RUBIDIUM require no de- 

 tailed notice from us. They were first found 

 in the solar spectrum, and resemble potassium. 



Fig. 400. Mottled soap-frames. 



AMMONIUM is only a conjectural metal. Ammonia, of which we have 

 already treated, is so like a metallic oxide that chemists have come to the 

 conclusion that its compounds contain a metallic body, which they have 

 named hypothetically AMMONIUM. It is usually classed amongst the 

 alkaline metals. The salts of ammonia are important, and have already 

 been mentioned. Muriate (chloride) of ammonia, or sal-ammoniac, is analo- 

 gous to chloride of sodium and chloride of potassium. It is decomposed 

 by heating it with slaked lime, and then gaseous ammonia is given off. 



THE METALS OF THE ALKALINE EARTHS. 



BARIUM is the first of the four metals we have 

 to notice in this group, and will not detain us 

 long, for it is little known in a free condition. Its 

 most important compound is heavy spar (sulphate 

 of baryta}, which, when powdered, is employed as 

 a white paint. The oxide of barium, BaO, is 

 termed baryta. 



Nitrate of Baryta is used for "green fire," 

 which is made as follows : Sulphur, twenty parts ; 

 chlorate of potassium, thirty-three parts ; and nitrate 

 of baryta, eighty parts (by weight). 



CALCIUM forms a considerable quantity of our 

 earth's crust. It is the metal of lime, which is 

 the oxide of calcium. In a metallic state it 

 possesses no great interest, but its combinations are very important to us. 

 Lime is, of course, familiar to all. It is obtained by evolving the carbonic 

 acid from carbonate of lime (CaO). 



The properties of this lime are its white appearance, and it develops 



Fig. 401. Soda furnace. 



