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On the Chemical Constitution of Brewsterite. By Aethur 

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



The formula of 3 ^.* \ Si '+ 4 Al Si^ + 24 H has been given 



by Berzelius for the constitution of this mineral * ; and, from a 

 statement made by Dr Brewster -f*, it would appear that Berze- 

 lius had founded this formula on an analysis of Retzius. It 

 gives, 



SiHca, .... 57.285 



Alumina, . . . 17-011 



Soda, 



:.} 



,. r ■ 7.764 



Liime, 



Water, .... 17.872 

 99.93S 



From some researches which I have made on the composition 

 of Brewsterite, I have been led to the conclusion that this for- 

 mula does not express the true constitution of the mineral, when 

 derived from its almost only locality, Strontian in Argyleshire, 

 and we must either suppose that some other mineral had been 

 analyzed by Retzius, or that certain of the above constituents 

 may be replaced by other substances. The specimens which 

 I have examined I have shewn to Professor Jameson, whose 

 name will be a sufficient sanction that no mistake exists as 

 to their identity with Brewsterite. The most remarkable re- 

 sult which I have obtained, is the detecting baryta and stron- 

 tia in the specimens under investigation ; and this circumstance 

 has induced me to offer this short notice on the subject, al- 

 though my researches are not yet so far completed as to en- 

 able me to present a regular analysis of the mineral. The first 

 specimen in which I found these earths, consisted of a kind of 

 c-.rystalline mass of concretions of Brewsterite, thickly studded 



• See Poggend. Anal. xii. 18. 



f Kdinhurgh Journal of Science, iv. 316. The formula has been there 



C C 



printed by mistake ^S* -f-4AS + 8Aq, instead of ^ S' + 4 A S' + 8 Aq, 



which is the fonnula corresponding to that in the text. In the Annal. de 

 Chim. ct Pbvs. xxxi. 21. it is given in the latter form. 



z2 



