ALUMINUM. 



159 



3. Add calcium sulphate : a white precipitate, insoluble in all 

 diluted acids, is formed immediately. 



4. Add potassium chromate or dichromate : a pale-yellow precipi- 

 tate of barium chromate, BaCrO 4 , is formed, which is soluble in 

 hydrochloric acid. 



5. Barium compounds color the flame yellowish-green. 



Summary of analytical characters of the alkaline earth-metals. 



24. ALUMINUM. 



Aliii 27 (27.04). 



Aluminum is the representative of the metals of the earths proper ; 

 all other members of this class are found in nature in very small 



QUESTIONS. 221. Which metals form the group of the alkaline 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? 226. What is Plaster-of-Paris, and 

 what is gypsum ; what are they uesd for ? 227. State composition and mode of 

 manufacturing bleaching-powder ; what are its properties, and how do acids act 

 upon it? 228. What is bone-black, bone-ash, acid phosphate, and precipitated 

 tricalcium phosphate ? How are they made ? 229. Give tests for barium, calcium 

 and strontium; how can they be distinguished from each other? 230. Which 

 compounds of barium and strontium are of interest, and what are they used for? 



