SeyherOs Analysis of the MaclureiU* ' 341 



strongly acid ; when treated with concentrated suFphuric 

 acid itetTervesced rapidly, disengaging a pungent gaz,givlng 

 rise to dense white vapours in the surrounding atmosphere, 

 its solution in the acid was but partial ; this sublimate thus 

 presented properties analogous to the Fluate of silica. To 

 investigate this matter more satisfactorily, I made the fol- 

 lowing comparative experiments, viz. a portion of the pow- 

 dered mineral was heated in a glass retort with an excess 

 of sulphuric acid. A mixture of three parts of Fluorspar 

 and one part of silica was then treated in the same manner, 

 the results obtained were precisely similar, a white pun- 

 I gent vapour was disengaged, ivhich condensed, on coming in 



contact with wafer, in the form of a white film, and the 

 neck of the retort was incrusted w^ith a white sublimate, 

 which effervesced with sulphuric acid, yielding a gaz which 

 presented the properties of Fhio-siHcic acid. These ex- 

 periments clearly demonstrated, that Fluoric acid was a 

 constituent of the mineral under examination, and I was 

 induced to repeat the experiments above stated according 

 to Professor Klaproth's method, but they were not j 

 «d with better success; on examiag the silica, obtai 

 this manner, 1 observed that it possessed certain proper- 

 ties, which proved that it had retained Fhioric acid; w^hen 

 thrown into water it decrepitated and rendered the Hquor 

 acid ; with sulphuric acid it effervesced violently, yielding 

 Fluo-sihcic acid : the silica, therefore, was intermixed 

 '^ith Fluate of potash and silica, a compound described by 

 Gray Lussac* and Thenard* They state, that potash com- 

 bines with siHca and Fluoric acid, forming a compound 

 which requires six or seven hundred times its weight of 

 Water to dissolve it. I also ascertained, that the magne- 



attend- 

 ned in 



sia, although precipitated by an excess of caustic or carbo- 

 nated alcah, likewise retained a portion of the Fluoric acid ; 

 the cause of my not having obtained any Fluate of Lime 

 from the solutions above mentioned, was thus rendered 

 apparent. I thought to obviate this difficulty in employing 

 Soda instead of Polash, in this manner I succeeded in ob- 

 taining some Fluate of Lime, but T ascertained, that the 

 Silica and magnesia still retained a portion of the acid and 

 at length after various experiments, I resorted to the 

 n)ethoa employed, so successfully, by Professor Berzelius 



• RechercLes phjaico-Chimiques vol. ii. p* 19- 



Vol, V. 41 



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