460 P. E. Browning — Quantitative separation of 



barium after the manner suggested by Dr. F. W. Mar,* pre- 

 cipitating with an excess of sulphuric acid in the presence of 

 hydrochloric acid. The mean of closely agreeing results was 

 taken as the standard. Preliminary experiments on the 

 bromides formed in this way gave encouraging results, the 

 barium salt appearing to be almost completely insoluble while 

 the strontium salt dissolved freely. The first series of ex- 

 periments were directed toward a quantitative determination 

 of the solubility of barium bromide in the alcohol. Definite 

 portions of the standardized solution of barium bromide were 

 measured from a burette into counterpoised beakers of about 

 50 cm 3 capacity and weighed as a check on the burette reading. 

 This solution was then evaporated to dryness, and the residue 

 was dissolved in a few drops of water and boiled with 10 cm 3 

 of amyl alcohol. The separating bromide was filtered off on 

 an asbestos felt contained in a perforated platinum crucible, 

 the whole having been previously ignited and weighed. The 

 crucible containing the bromide was at first dried at 140°- 

 150° C. in an air bath after the manner described in the 

 previous papers, and weighed. The unsuccessful attempt to 

 get a constant weight, however, proved the impossibility of 

 weighing as bromide, the weight decreasing rapidly with each 

 successive drying. It was deemed best accordingly to dissolve 

 the bromide from the felt into a beaker placed to receive it, 

 and to precipitate with sulphuric acid in the presence of hydro- 

 chloric acid, after the same manner followed in the determina- 

 tions of the standards. The precipitated sulphate, which in a 

 few minutes settles completely, was filtered off upon the same 

 felt from which the bromide had been dissolved, dried, ignited 

 to low redness, and weighed. Series I gives the results of 

 several experiments made after this manner which show the 

 solubility of the barium salt to be about 0*0013 grm. on the 

 oxide in 10 cm. 3 of amyl alcohol. The filtrate after boiling 

 with amyl alcohol was evaporated and the residue was treated 

 with sulphuric acid and weighed ; or the filtrate was precipi- 

 tated directly by adding sulphuric acid, enough ethyl alcohol 

 being added to secure thorough mixture. The amount of sul- 

 phate found agreed uniformly with the loss determined in the 

 residue after boiling. A portion of the salt which dissolved in 

 the alcohol on being examined before the spectroscope gave 

 only the green bands characteristic of barium. 



Series I. 





BaO taken. 



BaO found. 



Error. 



(1) 



0*1234 grm. 



0-1222 grm. 



0-0012— grm 



(2) 



0-0824 " 



0-0809 " 



0-0015 — 



(3) 



0-0823 " 



0-0809 " 



0-0014 — 



(4) 



0-0818 " 



0-0803 " 



0-0015 — 



(5) 



0-0733 " 



0-0720 " 



0-0013 — 



* This Journal, ili, 288. 



