604 PROCEEDINGS OF THE AMERICAN ACADEMY. 



of strontic bromide,* and was therefore no less pure than this 

 specimen. The carbonate had been prepared in the following manner. 

 The so-called " pure" strontic chloride of commerce was dissolved in 

 water, treated with ammonic hydrate and a little carbonate, and filtered 

 from the precipitate containing iron, aluminum, and so forth. To the fil- 

 trate was added an excess of sulphuric acid, and the precipitated strontic 

 sulphate was thoroughly washed with dilute sulphuric acid, and then with 

 pure water, in the hope of freeing it from magnesium and calcium. 

 When the wash water became neutral to methyl orange the precipitate 

 was treated with enough ammonic carbonate solution to convert about 

 half of it into carbonate, and the mixed precipitate was then washed 

 with water by decantation until only a very small constant trace of 

 sulphuric acid (due to strontic sulphate) was found in the decantate. The 

 carbonate was then decomposed by pure hydrochloric acid, and the solu- 

 tion was allowed to stand in a glass flask for nine months over the unde- 

 composed sulphate, with occasional shuking.f Thus all but a minute 

 trace of the barium was eliminated. Tlie strontic chloride was decanted, 

 the sulphate washed once with water, and the filtered decanted liquid 

 was evaporated in a platinum dish until most of the free hydrochloric 

 acid had been expelled. The dissolved residue was neutralized with 

 ammonia, shaken with a little ammonic carbonate, and then filtered. To 

 the greatly diluted filtrate was added an excess of pure ammonic car- 

 bonate, and the precipitate was washed until the wash water was free 

 from chlorine. The strontic carbonate was dissolved in nitric acid 

 which had been twice distilled in platinum, and the nitrate was crystal- 

 lized twice successively in a platinum dish. Each quantity of crystals 

 was washed with small quantities of water and three or four additions of 

 alcohol. The first mother liquor, upon being fractionally precipitated by 

 means of alcohol, showed distinct traces of calcium in the extreme solu- 

 tion ; thus Barthe and Faliere's method was not capable of freeing the 

 substance wholly from calcium. The second nitrate mother liquor 

 showed no trace of calcium upon the most careful spectrometric scrutiny, 

 although the test is one of very great sensitiveness ; therefore the 

 crystals could have contained none.J This effectual elimination of cal- 

 cium was due no doubt to the difTerence in crystalline form between the 

 calcium and strontium salts. 



* Tlicse Proceedings, 30, 377 (1894). 



t Barthe and Falieres, Journ. Cliem. Soc, Abs. 1892, p. 1277. Bull. Soc. Cliim., 

 [3], 7, 104. 



t Richards, These Proceedings, 28, 7 (1893). 



