and Laboratory Methods. 1289 



MICRO-CHEMICAL ANALYSIS. 

 XIII. 



STRONTIUM. 



We can employ, for the detection of this element : , 

 I. Sulphuric Acid. 

 II. Oxalic Acid. 



III. Sodium Tartrate. 



IV. Ammonium Bichromate. 



V. Primary Sodium Carbonate. 



None of these reagents can be considered as giving, at once, a characteristic 

 and reliable test for strontium in the presence of calcium and barium or mem- 

 bers of the magnesium group. It follows, therefore, that the detection of stron- 

 tium is often a matter of not a little difficulty. When dealing with mixtures of 

 the alkaline earths it is necessary to proceed as directed wnA&x— Separation of the 

 Calcium Group — methods which will be found immediately following the reac- 

 tions for Barium. 



/. Sulphuric Acid added to solutions containing salts of Strontium leads to the 

 separation of Strontium Sulphate. 



SrCl2 -f HaSO^ = SrS04 + 2HC1 



Method. — To the drop to be tested add a drop of dilute sulphuric acid. A 

 granular precipitate results. Add another large drop of the reagent, heat, and if 

 insufficient liquid remains add more acid. The heating is continued until dense 

 white fumes of SO5 are given off in abundance. Allow the preparation to cool 

 and examine at once. At first globular forms and rhombic plates appear, later, 

 these develop into more or less irregular fusiform crystals which generally grow 

 to crosses with two of the arms very short. Fig. 50. 



Instead of recrystallizing from sulphuric acid we 

 can employ hydrochloric acid. If the latter method 

 is believed to be preferable, proceed as follows : after 

 adding the reagent in sufficient amount to insure com- 

 plete precipitation, carefully draw off the supernatant 

 solution (or filter or whirl in the centrifuge). Wash 

 the precipitate with hot water to remove any free acid 

 and soluble salts, then add several drops of strong 

 hydrochloric acid. Heat the preparation to boiling, 



draw off, allow to cool, and examine. If after a short 



1 11-1 I I I I I 



time no crystals separate, concentrate the solution by \-pvy..o.o\'nm. 



heating. Strontium sulphate crystallizes from hydro- '^' ^°' 



chloric acid in the form of square and rectangular plates, long, thin prisms, and 



sheaves of acicular prisms. Fig. 51. 



Remarks. — As already stated under Calcium, the addition of sulphuric acid to 



