136 METALS AND THEIR COMBINATIONS. 



Sulphuretted lime, Calx sulphurata, is a mixture of calcium 

 sulphide and sulphate, obtained by heating in a crucible a 

 mixture of equal parts of sulphur and calcium oxide. 



Analytical reactions. 



1. Add to solution of a calcium salt, the carbonate of either 

 potassium, sodium, or ammonium : a white precipitate of cal- 

 cium carbonate is produced. 



2. Add phosphate of sodium to neutral solution of calcium : 

 a white precipitate of calcium phosphate is produced. 



3. Add ammonium (or potassium) oxalate to a calcium solu- 

 tion : a white precipitate of calcium oxalate is produced, which 

 is insoluble in acetic, soluble in hydrochloric acid. 



4. Sulphuric acid or soluble sulphates produce a white pre- 

 cipitate in highly concentrated solutions of calcium, but not in 

 dilute solutions. 



5. Calcium compounds impart a reddish-yellow color to the 

 flame. 



Barium, Ba h = 137. Strontium, Sr = 87.5. Both metals are 

 but rarely met with in nature. Barium occurs chiefly as sul- 

 phate or heavy-spar, BaS0 4 , and strontium as sulphate or car- 

 bonate. 



From the native sulphates the other salts may be made by 

 first converting them into sulphides, by heating with charcoal in 

 crucibles : 



BaSO 4 + 4C = BaS + 4CO. 



When the sulphide is dissolved in hydrochloric acid, barium 

 chloride is formed and sulphuretted hydrogen liberated : 



BaS + 2HC1 = H 2 S + BaCl 2 . 



By precipitating the barium chloride solution with sodium 

 carbonate, barium carbonate is obtained : 



BaCl 2 + Na 2 C0 3 = 2NaCl + BaCO 3 . 



By dissolving barium carbonate in the various acids the cor- 

 responding salts are obtained. For instance: 



BaC0 3 + 2HNO 3 = H 2 O + C0 2 + Ba2NO ( . 



