On the Cficmkal Composition of Harmotome. 37 



And, in 100 parts, 



Silica, 47.04 



Alumina, 15.24 



Baryta, ^ 20.86 



Liime, 10 



Potash, 88 



Soda, 84 



Peroxide of Iron, 24 



Water, 14.92 



100.11 



After I had ascertained the existence of alkalies in the crystals 

 of the new form, I submitted to chemical examination by a si- 

 milar process a portion of the barytic harmotome of Strontian of 

 the ordinary form, and obtained cubical crystals, the solution of 

 which, when mixed with muriate of platinum, and evaporated at 

 a gentle heat, afforded on resolution a small quantity of minute 

 yellow scales; and by subsequent spontaneous evaporation, crys- 

 tals of the chloride of sodium and platinum were formed. I then 

 examined some small twin crystals of barytic harmotome from An- 

 dreasberg, in the Hartz, which was, I believe, the locality of 

 the specimen analyzed by Klaproth, and obtained a like result. 

 It seems, therefore, extremely probable, that it will be found 

 universally, that barytic harmotome contains small quantities of 

 potash and soda*. 



The existence of potash and lime in the barytic harmotome 

 of strontian, appears to afford an additional link of connexion 

 between the two varieties into which harmotome has been di- 

 vided by foreign chemists, baryta in the one being supposed to 

 be replaced by lime and potash in the other. The constitutions 

 of the two varieties have not yet, however, been accurately re- 

 conciled to one another. The Berzelian formula of KS* -f 2 C 

 S*-|-10 A S*-|-15 Aq correctly represents the composition of the 

 lime harmotome, according to the analyses of Gmelin and 



• I am not aware tliat potash has before been observed in a proper bar j tic 

 harmotome. After I had detected the two alkalies in the strontian harmo- 

 tome, I observed in Berzelius' Jahres Bericht, 6th year, p. 284, an allusion 

 to some unfinished researches of L. Gmelin, showing the presence of soda in a 

 barytic harmotome, but I have never seen any further account of these re- 

 searches. 



