378 PROCEEDINGS OP THE AMERICAN ACADEMY. 



the sulphate into carbonate. The washed strontic carbonate having 

 been dissolved in a slight excess of hydrochloric acid, the residual sul- 

 phate was allowed to remain in the solution for a week. After filtra- 

 tion, evaporation to dryness in platinum, solution, a second filtration, 

 treatment with a little ammonic hydrate and carbonate, and yet an- 

 other filtration, the strontic chloride was converted into carbonate by 

 means of purified ammonic carbonate.* After a very complete wash- 

 ing the strontic carbonate was dissolved in pure nitric acid in a plati- 

 num dish. The nitrate was crystallized, dried at 150°, recrystallized. 

 washed with alcohol with the aid of the pump, dried, dissolved, and 

 stirred with a little pure strontic carbonate for a week. The filtrate 

 containing pure strontic nitrate was diluted, brought to boiling in a 

 platinum dish, and poured in a fine stream into a boiling solution of 

 pure ammonic oxalate f also contained in platinum. The strontic 

 oxalate was washed with the purest water upon the filter pump, 

 until no ammonia could be detected upon boiling the filtrate with 

 sodic hydroxide. Nessler's reagent still showed a trace of ammo- 

 nia ; but since this could easily be expelled by ignition, and the pre- 

 cipitate was very hard to handle, the washing was not carried further. 

 After drying and powdering, the oxalate was converted into carbon- 

 ate by ignition at a full red heat. The product was now ground 

 in a mortar with an equivalent amount of pure ammonic bromide, J 

 and the whole was gently ignited in a large platinum dish until no 

 more ammonia was evolved. The hundred grams of strontium bromide 

 thus obtained formed a pure white translucent cake upon fusion in a 

 large platinum crucible. The cake was dissolved in water, and the 

 alkaline solution, after havingr been boiled for some time, was neutral- 

 ized with sulphuric acid. The clear filtrate from the strontic sidpliafe 

 was now evaporated to a volume of about a hundred and twenty cubic 

 centimeters, and diluted with two hundred cubic centimeters of the 

 purest alcohol. The mixture was allowed to stand for a day, in 

 order that the strontic sulphate and any trace of baric sulphate which 

 might remain should be precipitated, .and then filtered. After three 

 successive crystallizations from water, the substance was used for 

 Analysis 10; a further crop'of crystals from the purest mother liquor 

 served for Analysis 11. 



Considering the pains taken in the purification of even the lea?t 

 pure sample, it is not surprising tliat all of these samples gave quan- 

 titative results which proved them to be essentially identical. 



* See page 379. t See page 379. J See page 380. 



