200 



EDWARD DIVERS AND TAMEMASA HAGA 



the normal barium salt is prepared from the barium potassium or 

 barium sodium salt, namely, by dissolving the strontium sodium salt 

 in dilute hydrochloric acid and pouring the solution at once into slight 

 excess of a warm concentrated solution of strontium hydroxide, and 

 repeating the operation twice, or until all sodium has been removed. 

 So long as the re-precipitated salt contains sodium, it is a hard granu- 

 lar precipitate, hut when it is free from sodium, it separates as 

 glistening, thin, scaly crystals, which felt together into soft volumin- 

 ous flocks, which, dried on the tile, form coherent flakes retaining" 

 water in their interstices with great ohstiuacy, like the barium salt, to 

 which it has indeed much resemblance. It is more soluble in water 

 than the barium salt, and is actually soluble in hot water to a, con- 

 siderable extent. For analysis we comminuted its flaky mass and 

 pressed the particles between filter paper till it seemed quite dry. But 

 on exposure to air for days such a preparation continuously loses water 

 and much of it before the crystalline lustre sensibly diminishes. 



The freshly dried salt contains 12 mois, water, as the following 

 numbers show : — 



Tested after 1.4 days exposure, the water amounted to only 7 mois, 

 although efflorescence had only then just become apparent. The 

 strontium was then 35.61 per cent., while calculation for 7 mois, 

 water gives 35.66 per cent. 



By decomposing the normal hydroxy-Jead imidosulphonate with 

 ammonium hydrogen carbonate, so as to obtain a weak solution of 

 normal ammonium imidosulphonate, and then evaporating to a small 



