ACCOUNT OF A MINERAL FROM ORKNEY. 91 



Having found in some previous experiments tliat some iron 

 adhered to the .insoluble residue, 



1. It w^as digested with muriatic acid, which became of a 

 yellowish hue, and along wifh the iron took up a portion of 

 the earthy matter ; but this was precipitated on the addition 

 of water. Its solution was concentrated, and precipitated by 

 succinate of potassa. The precipitate, washed, dried, and 

 heated to redness in a platina crucible, afforded 0.1 grain, or 

 nearly so, of red Oxyde of Iron. 



2. The residue of the mineral was now mixt with three 

 times its weight of lamp-black, made into a paste with oil, and 

 subjected in a black-lead crucible for two hours, to the heat of 

 a smith's forge. The contents of the crucible were then 

 thrown into muriatic acid, which produced a brisk efferves- 

 cence: the muriatic solution was precipitated by sulphuric 

 acid ; it was then evaporated and heated, to expel the excess 

 of acid, and what water might adhere to it, and when weighed 



i:: 27.5 grains. 



1 he residue then consists of 27.5 sulphate of barytes, 

 And - 0.1 oxyde of iron. 



27.6 



In 100 grains, therefore, of the mineral from Orkney, we 

 have 



68.6 carbonate of strontites. 

 27.5 sulphate of barytes. 



2.6 carbonate of lime. 



0.1 oxyde of iron. 



988 

 1.2 loss (probably water). 



100.0 



m2 a 



