266 Dr T. THOMSON'S Account of the 



down the sulphuric acid. The sulphate of barytes was edulco- 

 rated, ignited, and weighed. 



The carbonates of barytes, lime, &c. were dissolved in mu- 

 riatic acid, and the alumina and oxide of iron were precipitated 

 by caustic ammonia. The liquid thus freed from alumina and 

 iron, was evaporated to dryness, and the dry salt digested in al- 

 cohol, which dissolved the muriates of lime and strontian, and 

 left the muriate of barytes. This last muriate was dissolved in 

 water, and the barytes thrown down by sulphate of soda, and its 

 weight determined in the usual way. 



The muriates of lime and strontian were converted into ni- 

 trates. The dry nitrates were digested in alcohol, which dissol- 

 ved the nitrate of lime, and left the nitrate of strontian. 



The quantity of carbonic acid was not determined experimen- 

 tally, but deduced from the quantity of strontian present in the 

 mineral. 



It is obvious that the mineral consisted of 



,. _ f Acid, 25.100 ) 



Sulphate of Barytes, | ^ ^^ j . 74.045 



Sulphate of Lin :.'. ^.436| 16.041 



Carbonate of Strontian, . . { ' JJJ } 



Silica, Alumina, Protoxide of Iron, ...... 8.050 



Moisture, .............. 0.565 



99.825 



If we consider the carbonate of strontian, the silica, the alu- 

 mina, protoxide of iron, and moisture, as accidental substances, 

 then the mineral is a compound of 



5 atoms sulphate of barytes, 

 2 atoms sulphate of lime. 



