SECT. i. METALS AND THEIR PROPERTIES. 3 



into atomic systems or molecules ; but there are sixty- 

 four which have never yielded to chemical analysis, and 

 are therefore believed to be respectively formed of only 

 one kind of atoms. Thirty-five of these are metals 

 found either pure or as ores, and sixteen are metals ex- 

 isting naturally in chemical combination with^ilkalies, 

 alkaline earths, or earthy bases, that is as salts, from 

 which they have been obtained by the analytical power 

 of electricity or other means. The thirteen remaining 

 simple substances are non-metallic : some are aeriform, 

 some solid, one liquid. 



The alkaline metals are sodium, potassium, lithium, 

 csesium, rubidium, and thallium. They are distin- 

 guished by their energetic affinities for, and the sim- 

 plicity of their compounds with, non-metallic elements. 

 They are never met with native, and are amongst the 

 most difficult metals to reduce from their ores, and their 

 spectra are remarkable for simplicity. Sodium and 

 potassium which have been such important agents in 

 spectrum science were reduced from their alkalies of 

 soda and potash by Sir Humphry Davy by means of the 

 voltaic battery, a discovery which led the way to the 

 reduction of many of the others. Lithium is a white 

 metal which burns brilliantly in air and oxygen; it 

 swims in naphtha, and is the lightest solid body known. 

 Csesium is the most energetic of all metals in its chemi- 

 cal affinities. 



The metals of the alkaline earths are barium, stron- 

 tium, calcium, and magnesium. They possess, like the 

 preceding, energetic affinities for the non-metallic ele- 

 ments, and are reduced with difficulty from their ores. 

 Barium is obtained from earth baryta : it is powerfully 

 alkaline, and its salts are colourless and poisonous. 

 Calcium is obtained from limestone, chalk, marble, and 

 gypsum, which are amongst the most abundant consti- 

 tuents in the crust of the earth ; it is a bright ductile 



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