N. 



«6o Mr. Smithson on a saline Substance 



salt, which had been recovered by evaporation from a filtere(f 

 solution of it, v^as made red hot in a platina crucible. On ex- 

 traction of the saline part by water, a very small quantity of 

 a black powder was obtained. Ammonia dissolved only part 

 of it, which was copper. The rest being digested with muriatic 

 acid, and prussiate of soda-and-iron added, a fine Prussian blue 

 was formed. 



r. From several of the foregoing experiments, it appeared' 

 that no sensible quantity of any of the mineral acids, besides 

 the sulphuric and muriatic, existed in combination with alkali 

 in this volcanic salt. But Mr. Tennant, whose many and 

 highly important discoveries have so greatly contributed to 

 the progress of chemical science, having detected disengaged 

 boracic acid amongst the volcanic productions of the Li pari 

 islands, and suggested that it might be a more general pro- 

 duct of volcanoes than had been suspected,* it became impor- 

 tant to ascertain whether the presence of any in this salt proved 

 Vesuvius likewise to be a source of this acid. Alcohol heated 

 on a portion of it in fine powder, and then burned on it, did not 

 however shew the least green hue in its flame. 



s. To ascertain the proportions of the ingredients of this 

 saline substance, the following experiments were made ; 



10 grains of sulphate of potash of the shops were dissolved 

 in 200 grains of water, and an excess of muriate of platina 

 added. The precipitate edulcorated with 100 grains of water, 

 and dried on a water bath, weighed 24,1 grains. 



iQ grains of the saline part of the native salt, treated pre- 

 cisely in every respect in the same way, afforded 17,2 grains 

 of precipitated muriate of platina-and-potash. 



• Trans, of the Gcolog. Soc. 



