1 1 6 M. Scheerer's Observations on Elaolith and 'Nepheline, 



feet accuracy, be subtracted from the quantity employed for 

 the analyses. But the flocks M. Bromeis considers to be alu- 

 mina, which was still retained in the silica, and was not dis- 

 solved on boiling in carbonate of soda. This, however, is 

 not the case ; for if these flocks are filtered and dried, they 

 form a powder which, before the blow-pipe with soda, gives 

 a perfectly clear glass. To be more surely convinced of the 

 nature of this residue, I decomposed 10 gr. of the white, and 

 10 gr. of the green elaeolith with hydrochloric acid- In 

 both cases I obtained from the silica sufficient quantities of 

 this residue to be able to examine it more accurately. I found 

 it to contain above § silica, and only a little alumina, and a 

 trace of the peroxide of iron ; it cannot, therefore, be added 

 to the alumina without committing an error. 3. M. Bromeis 

 conceives that alumina may still be contained in the silica, 

 separated from the heated alumina, by long digestion, in hy- 

 drochloric acid. The quantity of it can, however, be but ex- 

 tremely slight, as this residue acted before the blow-pipe as 

 pure silica. If, indeed, which is possible, it should still contain 

 a small quantity of alumina, it is certainly balanced by the 

 trace of silica, which is re-dissolved on boiling with hydro- 

 chloric acid ; for if the alumina and peroxide of iron, dis- 

 solved in hydrochloric acid, be again precipitated by ammo- 

 niac, the precipitate again heated and dissolved still gives 

 traces of silica*. 4. Of what does the residue consist which 

 remains on dissolving the chlorides of potassium and sodium ? 

 In the first analyses I always added it to the silica; but in so 

 doing I committed an error, as I subsequently found it to 

 consist of alumina, silica, lime, and at times magnesia. The 

 first analyses give, therefore, according to my formula, too 

 much silica. I was deceived by the insolubility of this re- 

 sidue in acids, but afterwards found that it did not give a 

 glass on being treated with soda before the blow-pipe. 



In the later analyses I have attended to all these points. 

 The powdered mineral was decomposed with dilute hydro- 

 chloric acid, which has the advantage, that the elaeolith dis- 

 solves in it to a clear fluid, and the particles of foreign unde- 

 composed mineral may easily be detected. 



After all the facts quoted, it seems to me fully established 

 that elasolith and nepheline contain 3 at. silica, 2 at. alumina, 



* That a portion of the silica is re-dissolved, may be explained in the fol- 

 lowing manner. Silica which, after incandescence, is insoluble in acid, 

 becomes soluble when fused with an alkali. But even this is not requisite ; 

 many other of the stronger 'jases have the property of rendering \t partly 

 soluble. 



