ACCOUNT OF A MINERAL FROM ORKNEY. 85 



and very deliquescent salt remained in the bottom of the cap- 

 sule. It was decomposed by oxalate of potassa, when a high- 

 ly insoluble substance, not soluble in excess of oxalic acid, was 

 obtained. Calcination, and the action of sulphuric acid, pro- 

 ved that the oxalate of lime had been formed. 



5. The greyish-white powder, which remained after the cal- 

 cination of the oxalate, was wholly soluble in water, and form- 

 ed a bulky precipitate with sulphuric acid. The washings of 

 this precipitate were not rendered turbid by phosphate of am- 

 >monia, nor was any change produced by the muriate of am- 

 monia. These experiments shew that the muriatic solution 

 of the mineral contained no magnesia, nor argil, nor any ap- 

 preciable quantity of iron. 



The peculiarity attending the action of concentrated nitric 

 and muratic acids on the mineral is worthy of notice, as afford- 

 ing an additional diagnostic mark between carbonate of stron- 

 tia and carbonate of barytes. It will be recollected that those 

 acids acted at first upon the mineral from Orkney, but that 

 the effervescence soon ceased, unless water were added. In 

 order to compare the two carbonates more accurately, the fol- 

 lowing experiments were instituted. 



a. A fragment of native carbonate of strontia from Strontian 

 was thrown into muriatic acid ; a strong effervescence ensued, 

 but soon ceased : it was however immediately renewed on the 

 addition of water ; just as had happened with the mineral from 

 Stromness. 



h. Into a portion of the same acid was dropt a fragment of 

 carbonate of barytes from Anglezark, which had been entirely 

 freed from loose particles ; no effervescence took place, until 

 water was added ; but when a portion of the same specimen, 

 reduced to powder, was thrown into a fresh portion of the 

 acid, effervescence instantly commenced. 



c. A 



