An Investigation of the "Chromate Method" for 



SEPARATING THE AlKALINE EaRTHS.* By HuBERT 



Bradford Vickery, Dalhousie University, Halifax. 



(Read 11 January 1915) 



This investigation was undertaken with the twofold 

 object of discovering the degree of sensitiveness of which 

 the ordinary "chromate method" for the separation of the 

 alkaline earths is capable, and also under what conditions 

 this sensitiveness may be increased. Incidentallj^ a con- 

 siderable improvement was made in the procedure. 



Throughout the experimental work the idea was kept 

 constantly in mind to have the conditions of working as 

 nearly as possible those which obtain in the manipulation 

 of the average student of qualitative analysis, and where 

 these have been changed, to make them very easily attainable,, 

 so that the j5nal quantitative results might fairly represent 

 the degree of accuracy obtainable in ordinary work. 



While several methods exist for the separation of the 

 alkaline earths which are extremely delicate, f they depend 

 largely upon the use of alcohol and ether to decrease the 

 solubility of the various precipitates, and hence are scarcely 

 suitable for class use. The chromate method, on the con- 

 trary, uses water solutions alone and obviates the necessity 

 for inconveniently long waits for complete precipitations, 

 thus greatly decreasing the time required for a single analysis 

 and making this method eminently suitable for use in class. 

 The procedure ordinarily followed t consisted in precipitating 

 the carbonate in strongly alkaline solution, magnesium being 

 held in solution by means of ammonium chloride. The 



* Contributiona from the Science Laboratories of Dalhousie University (Chemistry). 



t J. Am. Chem. Soc, 30, 611. (190'i). 



t G. S. Newth: Manual of Chemical Analysis, p. 35. 



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