FOR SEPARATING THE ALKALINE EARTHS. VICKERY. 33 



CALCIUM CARBONATE 



Conditions same as above. 



0.3 ins- of calcium gave no precipitate. 



0.5 ing. gave no precipitate. 



0.6 mg. gave very slight precipitate. 



0.8 mg. gave slight precipitate. 



1.0 mg. gave slight precipitate in 4 minutes. 



5.0 mg. gave precipitate almost at once. 

 10.0 mg. gave heavy crystallins precipitate at once. 

 It was found that a temperature much in excess of 70^ 

 caused an interaction of the carbonate with the ammonium 

 chloride, giving an evolution of carbon dioxide and resulting 

 in the solution of the precipitate or complete failure to form 

 a precipitate. 



In each case completeness of precipitation of a solution 

 containing 25 mg. of the metal was tested by filtering after 

 ten minutes and allowing to stand over night. Onl}^ in the 

 case of barium. did any deposit form and even in this case 

 it was in very small quantity. The precipitates were ex- 

 amined microscopically, but it was found that although the 

 crystals when falling from very dilute solutions were quite 

 easily differentiated, from more concentrated solutions 

 they were almost indistinguishable, especially since calcium, 

 and to a lesser extent barium, show a tendency to come down 

 as gelatinous masses from cool solutions. 



BARIUM CHROMATE 



Precipitating reagent, 3cc K2CrOi. Total volume of solu- 

 tion, lOOcc. 



In neutral solution, even one tenth of a milligram of 

 barium gave a cloudiness in five minutes, but in a solution 

 containing l-2cc acetic acid 2 mg. failed to give a precipi- 

 tate, while 2.5 mg. gave a slight one on standing a few 



Proc. & Trans. N. S. Inst. Sci. Vol. XIV. Trans. 3 



