FOR SEPARATING THE ALKALINE EARTHS. VICKEUY. 39 



Procedure IV. Precipitation of Strontium 



Evaporate to about 80cc and add 80cc of NH4Clfor 

 every 200 mg. of barium present; in no case less than 80cc. 

 Add 10-15cc (NH4)2 SO4 solution. Fine granular white pre- 

 cipitate indicates strontium. Heat to boiling and let digest 

 a few moments. Filter and wash with hot water. 



Notes — 1. Calcium, if present to the extent of 100 mg., 

 will precipitate at this point unless held in solution by a 

 large quantity of NH4CI. If a feathery precipitate in quite 

 large crystals appears on heating, it is probably calcium. 



2. Ammonium chloride inhibits the precipitate of 

 strontium to only a very slight extent. 



3. 15 mg. of strontium can be easily detected in 

 the presence of large amounts of barium. 



3. The confirmatory test should always be tried. 



Procedure V. Confirmatory test for Strontium. 



Boil the precipitated sulphate with ammonium carbonate 

 and neutralize with acetic acid. Concentrate to 10-20cc and 

 filter if necessary. Add saturated solution of Ca SO4 and 

 boil. Fine white precipitate confirms strontium. 



Note — 1. The strontium sulphate is converted to carbonate 

 by the ammonium carbonate and brought into solution by 

 the acid. The calcium is likewise converted but calcium 

 acetate cannot give a precipitate with calcium sulphate, while 

 the less soluble strontium sulphate separates at once on 

 heating. 



Procedure VI. Precipitation of Calcium. 



To the hot filtrate add NH4OH to strongly alkaline 

 reaction and then lOcc more. Add 20cc hot (NH4)2 C2O4 

 solution and stir. White precipitate indicates barium. 



Note — 1. 1 mg. of calcium can be easily detected in the 

 presence of 400 mg. of barium and strontium. 



