32 AN INVESTIGATION OF THE " CHROMATE METHOD " 



thus fixing a lower limit to the sensitiveness of the particular 

 precipitation, and ensuring uniform conditions. 



The reagents used were: — Ammonia sp. gr. .90 (equival- 

 ent to three times the volume of sp. gr. .96). 



Ammonium Chloride 10% 



Ammonium Carbonate 25% 



Potassium Chromate 5% 



Ammonium Sulphate 10% 



Ammonium Oxalate 5% 



Acetic Acid 50^ 



BARIUM CARBONATE 



The precipitating reagents were 3cc NH4OH, lOcc 

 XH4CI, lOcc (NH4)2C03. The total volume of the solution 

 was lOOcc. 



0.5 mg. of barium gave no precipitate. 



1.0 mg. gave no precipitate. 



2.0 mg. gave no precipitate. 



3.00 mg. gave very slight deposit on lines of rubbing 



with glass rod. 

 5.0 mg. gave slight deposit. 

 7.0 mg. gave verj^ slight precipitate. 

 10.0 mg. gave feathery crystalline precipitate in few 



moments. 

 25.0 mg. gave feathery precipitate almost at once. 



STRONTIUM CARBONATE 



Conditions same as above. 



0.5 mg. of stronium gave no precipitate. 



1.0 mg. gave very slight precipitate in 5 minutes. 



2.0 mg. gave slight precipitate in four minutes. 



4.0 mg. gave decided precipitate in few monents. 

 10.0 mg. gave fairly heavy precipitate, but not coming 



down instantly. 

 25.0 mg. gave heavy precipitate at once. 



