20 PROCEEDINGS OF THE AMERICAN ACADEMY 



room, and, since the work was not fruitful, they may well be 

 omitted. 



Because of all these unsatisfactory results the baric hydrate was 

 converted directly into baric bromide and bromate by the addition 

 of pure bromine similar to that used in the preparation of Sample 

 III. The large amount of bromide filtered off from the bromate 

 was half crystallized out by boiling down the mother liquor in a 

 platinum dish, treating with alcohol, and cooling. The mother 

 liquor from these crystals contained most of the strontium. The 

 solid was dissolved, boiled down, treated with alcohol and cooled; 

 and the new crystals were washed four times with alcohol. After 

 repeating this round of operations once again, the mother liquor 

 showed no trace of strontium.* The pure crystals yielded a faintly 

 brownish mass upon fusion, and this in turn left a brownish pre- 

 cipitate upon solution. The clear filtered liquid was boiled down 

 and treated with alcohol just as described above. The crystals were 

 again fused, and again subjected to the same succession of opera- 

 tions. For the last time the crystals were raised to a dull red heat 

 b}" means of a spirit lamp, and the residue was dissolved in the 

 purest water in a platinum dish, allowed to stand exposed to the air 

 until neutral, filtered, recrystallized twice more, and washed with 

 the purest alcohol. The resulting material was designated IV. a 

 (Analyses 13, 14, 15). The last mother liquors were evaporated, 

 and yielded IV. b (Analysis 12). Only about fifteen grammes of 

 such pure material were obtained from a kilogramme of the baric 

 hydroxide which served as the starting point. The earlier mother 

 liquors containing strontium were used for the preparation of pure 

 hydrobromic acid. 



The fifth method for the preparation of baric bromide was the 

 most complicated of all. A large amount of a solution of baric 

 chloride ("purissimum ") was allowed to stand for eighteen hours 

 after the addition of a little pure baric hydrate and carbonate. To 

 the filtered and slightly acidified liquid was added enough potassic 

 chromate to precipitate about half the barium, the potassic chro- 

 mate having been previously purified by continued shaking with a 

 little baric chloride and hydrochloric acid, and by subsequent filtra- 

 tion. The large mass of baric chromate was washed by decantation 



* This method of freeing baric from strontic bromide suggests P. E. Brown- 

 ing's work with amj-1 alcohol, published since the experiment recorded above 

 was completed. (Am. Journ. Sci., [3.] XLIV. 459.) 



