ACCOUNT OF A MINERAL FROM ORKNEY. 87 



2. The water employed to wash the powder C. I. was 

 evaporated, and crystals of sulphate of potassa were formed. 



3. The muriatic solution (C. 1.) obtained by decomposing the 

 sulphate by carbonate of potassa, when evaporated, yielded ta- 

 bular crystals, persistent in the air, which, placed in the wick 

 of a candle, tinged its flame of a yellow or greenish-yellow 

 hue \ and when dissolved in water afforded an instant precipi- 

 tate with sulphuric acid, and with the most diluted solutions 

 of sulphate of soda. 



4. Another portion of the insoluble residue was boiled with 

 eight parts of concentrated sulphuric acid in a platina cup, 

 and was wholly dissolved ; but on cooling, it separated in aci- 

 cular crystals around the edge of the containing vessel. These 

 crystals were acidulous, even when dipt into water, which 

 resolved them immediately into an insipid powder which was 

 a neutral sulphate. When exposed to the air this powder was 

 more slowly formed. 



5. A third portion of the insoluble residue was digested 

 with muriatic acid, under the idea that its colour indicated the 

 presence of iron. The acid became of a yellowish colour, 

 and afforded a rich blue precipitate with prussian alkali. 



These experiments prove, that the residue consists chiefly 

 of Sulphate of Barytes. In C. 1. the process of Klaproth was 

 employed ; and at each successive step, fresh portions of the 

 sulphate were decomposed, by the united affinities of sulphuric 

 acid for potassa, and of carbonic acid for barytes. In C. 4. 

 Moretti's process was followed *, and, to verify his results, 

 comparative experiments were tried. 



a. Artificial sulphate of strontia was boiled in a platina cruci- 

 ble with 8 parts of concentrated sulphuric acid ; a perfect so- 

 lution 



* See Thomson's Annals, vol. iv. 395. 



