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On the Chemical Cofistitution of Brewsterite. By Arthur 

 CoNNELL, Esq. F. R. S. E. Communicated by the Author. 



Xhis mineral was first characterized, from its crystalline form, 

 as a distinct species by Mr Brooke, who also gave it its pre- 

 sent name *. 



It would appear that, some years ago, a specimen of the mi- 

 neral was sent by Dr Brewster to Berzelius, for the purpose of 

 being analyzed ; and that Berzelius wrote back in answer, that 

 it had been already analyzed by Retzius, conformably to the 



C 



formula -^ S*' -h 4 A S^ -f 8 A ^f, and called by him Prehniti- 



form Stilbite ■(•. This formula, or the corresponding chemical 

 one, has been retained by Berzelius J ; and I am not aware that 

 any other statement respecting the constitution of the mineral 

 has been given to the public. The locality of the mineral ana- 

 lyzed by Retzius is not stated. The formula of Berzelius gives §, 



Silica, 57-285 



Alumina, .... 17*011 



it%} 7-^" 



Water, 17872 



99-932 



In a former notice on this subject ||, I shewed, from an ex- 

 amination of some pure crystals of Brewsterite from Strontian 

 in Argyllshire, that it contained strontia and baryta, and no 

 notable quantity of lime. I also shewed that it contained no 

 alkali, and concluded that the formula of Berzelius did not ap- 

 ply to the mineral, at least when derived from the above loca- 

 lity, unless the formula and composition could be accommodated 

 to one another by the aid of the doctrine of replacement. 



It became a matter of some interest to establish by a regular 



• Edin. Phil. Journal, vol. vi. p. 112. 

 + Edinb. Jour, of Science, vol. iv. p. 316. 

 X Die Anwendung des Lothrohrs, 2te Auf. S. 168. 



§ This calculation is made by the atomic weights of Berzelius. AH the 

 subsequent calculations of formulae are made by those of Dr Thomson. 

 II Edinb. New PhiL Jour. No. 16. p. 355. 



