56 WRITINGS OF JAMES SMITHSON. 



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, be- 

 sides 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 con- 

 tributed to the progress of chemical science, having detected 

 disengaged boracic acid amongst the volcanic productions 

 of the Lipari islands, and suggested that it might be a more 

 general product of volcanoes than had been suspected,* it 

 became important 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 dis- 

 solved 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 21.1 grains. 



10 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. 



If 24.1 grains of this precipitate correspond to 10 grains 

 of sulphate of potash, 17.2 grains of it correspond to 7.14 

 grains of this salt. 



It has been seen (ri) that 10 grains of the saline part of 

 this volcanic salt would have afforded 12.55 grains of sul- 

 phate of barytes. 



But 7.14 grains of sulphate of potash form only 9.42 

 grains of sulphate of barytes,f and therefore the remaining 

 3.13 grains of sulphate of barytes would be produced by the 



* Trans, of the Geolog. Soc. 



f Dr. MARCET on Dropsical Fluids. 



