ELISHA MITCHELL SCIENTIFIC SOCIETY. 9I 



the amount of barium chromate held in solution was [doubled. 

 Larger amounts, up to 7.5 per cent, did not very notably increase 

 this amount held in solution. Obviously, then, acetic acid increases 

 the solubility of the barium too much to be used in the separation. 

 Hydrochloric acid greatly increases the amount of barium held in 

 solution. 



Ammonium chloride, added to the potassium bichromate solution, 

 makes it capable of dissolving or holding in solution much more 

 barium chromate. In our experiment the amount held in solution 

 was more than five times as great as it should have been. 



Sodium acetate in the proportion of about five grams to the hun- 

 dred cubic centimeters of liquid, prevents any of the barium from 

 being held in solution. On taking 50 c. c. of the filtrate from this 

 mixture, no precipitate was gotten with sulphuric acid, showing the 

 almost absolute absence of barium. The same proportion of sodium 

 acetate had no effect upon a mixture of the solutions of strontium 

 chloride and potassium bichromate, as at the end of eleven days no 

 precipitate was visible. 



For qualitative work, these tests were amply suflBcient to give the 

 proper conditions for the separation of the two metals. The potas- 

 sium bichromate should be in the proportion of twenty or more 

 grams to the litre, and enough sodium acetate should be added to 

 form five or six per cent, of the whole. 



Chemical Laboratory, U. N. C. 



12 



