A Modification of the Procedure for the Qualitative 

 Separation of the Metals of the Alkaline-Earth 

 Group. — By C. B. Nickerson, M. A., Professor of Chem- 

 istry, Dalhousie University. 



(Read 16 April, 1923) 



The separation of the ions, Barium-Strontium-Calcium, has 

 always furnished something of a problem to teachers of Qualita- 

 tive Analysis. Although several very excellent methods of 

 analysis are available, the writer has found them to be some- 

 what tedious of manipulation, and requiring more time for a 

 successful separation than is usually convenient for the ordinary 

 college class in Qualitative Analysis. It is not the purpose of 

 this paper to go into the various reasons why the separation of 

 these ions is a difficult one, but rather to describe a method which 

 has been used successfully by the writer in his classes for a 

 number of years. 



This method depends upon the separation of calcium from 

 strontium by taking advantage of the solubility of calcium 

 sulphate in a boiling solution containing a considerable quantity 

 of ammonium acetate. The solubility of calcium sulphate, and 

 the insolubility of strontium sulphate in solutions of ammonium 

 sulphate and ammonium chloride have been known for a long 

 time and several procedures for the qualitative separation of 

 these ions are based on this principle. The substitution of 

 ammonium acetate for the chloride or sulphate however, has 

 been found to be generally more suitable and also, in the hands 

 of students, capable of greater accuracy. The separation of 

 barium ion from calcium and strontium ions by the well known 

 acetic acid-chromate method has also been studied quantita- 

 tively, and a modification of the usual method of separation 

 proposed. 



Proced^lre. 



Treatment of the Filtrate from the Sulphides of the Fe.- 

 Zn. etc. group. 



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