58 



CHEMISTRY. 



Prop. — A grayish- white metal, heavier than water ; has a strong 

 affinity for oxygen ; malleable.— Symb. Ba. ; it forms two oxides. 



Protoxide or Baryta, BaO.— Occurs in nature as.a carbonate and 

 sulphate ; may be obtained by decomposing the nitrate by heat. It 

 has a strong affinity for water, forming with it a hydrate, with the 

 evolution of heat. The hydrate is a white powder, resembling 

 slacked lime ; its solution, like lime-water, attracts carbonic acid 

 from the air. 



Peroxide of barium, BaO^, is used in making the peroxide of 

 hydrogen. 



The salts of baryta are chiefly remarkable for their high specific 

 gravity ; the most important are the carbonate, sulphate, and nitrate. 

 The sulphate is very insoluble. The soluble salts are poisonous. 

 Chlorine, iodine, bromine, and sulphur, form compounds with 

 barium. 



Test for baryta. — It forms a very insoluble sidphate, 



STRONTIUM. 



Procured as barium. — Symb. Sr. Forms two oxides. 



Protoxide,— Strontia, SrO,— prepared like baryta, which it much 

 resembles. Its other compounds are similar to those of baryta. 



Test. — It communicates a blood-red colour to the flame of the 

 blowpipe. 



CALCIUM. 



A silver- white metal, procured like barium ;— forms with oxygen 

 two compounds. Symb. Ca. 



Protoxide, Lime, CaO,— obtained by heating the native car- 

 bonates. 



Prop. — Lime is white, — infusible, — has a strong affinity for water, 

 forming with it a solid hydrate, with the evolution of much heat ; 

 this is seen in the common process of slaking. The hydrate is far 

 less soluble in water than those of baryta and strontia ; it is more 

 soluble in cold than in hot water ; lime-water is thus made. Ex- 

 posed to the air, it attracts carbonic acid, forming a pellicle : hence 

 it is a good test for carbonic acid ; it has an alkaline reaction. The 

 hardening of mortar is probably due to the gradual absorption of 

 carbonic acid, or to the combination of the sand and lime, forming 

 a silicate. 



The most important salts of lime are the sulphate, carbonate, 

 phosphate, and hypochlorite. 



Sulphate of lime or Gypsum, CaO + SOg, is found native; the 

 native crystals are called selenite. 



Prop. —A. sparingly soluble salt ; forms with water a hydrate ; it 

 is found in most spring water. 



