340 Seyhcrfs Analysis of the Macluretie. 



silver crucible with nine grammes of caustic potash ; when 

 the matter had cooled, it was treated with water, and the 

 solution was filtered, the filtered liquor was supersaturated 

 with muriatic acid, the solution was treated with an excess 

 of ammonia, this produced a gelatinous precipitate, which 

 was separated by filtration, the filtered liquor was again 

 treated with a slight excess of muriatic acid, and boiled to 

 expel the carbonic acid, it was then exactly neutralized 

 with ammonia, and treated with lime water, no precipitate 

 was formed, and it was treated with muriate of lime with 

 the same result ; these experiments induced me to believe, 

 that the mineral in question contained no fluoric acid, 

 nevertheless, to reduce thisfact to greatercertitude,! follow- 

 ed precisely the method employed b^i Professor Klaproth, in 

 his analysis of the Pycnite, viz. three grammes of the sub- 

 stance, reduced to a fine powder, were calcined in a sil- 

 ver crucible, with caustic potash, the silica was separated 

 in the usual vvay, the liquor was treated with an excess of 

 sub-carbonate of soda, to precipitate the Magnesia ; after 

 tiltration the carbonic acid was expelled, from the liquor, 

 by an excess of muriatic acid and subsequent ebullition, it 

 was then exactly neutralized with ammonia, and treated 

 with a solution of pure lime and muriate of lime, without 

 any precipitate having been produced by these reagents. 



My attempts to discover Fluoric acid having thus proved 

 fruitless, 1 determined to direct my attention to the ap- 

 pearances which occurred during the calcination of the si- 

 lica in the two preceding analyses, the sublimate was very 

 minute in quantity, I prepared some of it from silica ob- 

 tained, from the mineral, as in the preceding analyses. The 

 silica was dried, at a moderate temperature, and then ex- 

 posed to a red heat, in a small glass retort ; before the 

 glass was reddened, there passed over a small quantity of 

 water, and a white sublimate appeared on the dome of the 

 retort ; as the heat increased, this sublimate descended 

 into the neck, and lastly, partially, into a receiver adapted 

 to condense it. After the calcination, the retort was re- 

 moved from the fire, the receiver contained ot ly a very 

 small portion of the sublimate, and a vapour possessing a 

 a very pungent odour, which reddened litmus with great 

 energy : the sublimate incrusting the neck of the retort 

 was colourless, and very acid to the taste, in water it dis- 

 solved partially, leaving a flaky residue, the liquor became 



