BARIUM STRONTIUM. 137 



Strontium compounds may be made by an analogous process. 

 Xeither barium nor strontium enters into any officinal prepara- 

 tion. Strontium is chiefly used in the form of nitrate for pyro- 

 technical purposes, as it imparts a beautiful red or crimson color 

 to the flame. 



Barium is chiefly used as sulphate for adulterating white-lead 

 and other colors, or as chloride or nitrate as reagents for sul- 

 phuric acid or soluble sulphates. 



Barium salts are poisonous; antidotes are sodium and magne- 

 sium sulphates. 



Analytical reactions of barium and strontium. 



1. Like calcium solutions, those of barium and strontium give 

 a white precipitate with soluble carbonates or phosphates. 



2. Barium gives with neutral potassium chromate a pale 

 yellow precipitate of barium chromate; calcium and strontium 

 do not. 



3. Barium and strontium solutions are precipitated by solu- 

 tion of calcium sulphate; calcium solutions are not. 



4. Barium gives with sulphuric acid, or with soluble sulphates, 

 an immediate white precipitate of barium sulphate which is en- 

 tirely insoluble in all acids; strontium sulphate is less insoluble, 

 and calcium sulphate may be completely dissolved in water or 

 in dilute hydrochloric acid. 



5. Barium colors the flame pale green, strontium crimson, 

 calcium reddish-yellow. 



6. Barium, strontium, and calcium compounds are colorless, 

 unless the acid has a coloring effect. 



QUESTIONS. 



221. Which metals form the group of the al-kaline earths, and in what 

 respect do their compounds differ from those of the alkali-metals? 



222. How is calcium found in nature? 



223. What is burned lime; from what, and by what process is it made, 

 and how does water act on it ? 



224. What is lime-water; how is it made, and what are its properties? 



225. Mention some varieties of calcium carbonate as found in nature, 

 and how is it obtained by an artificial process from the chloride? 



