dS2 Account of some Experifnenls 



Ammonia seems to me to separate completely the sife.\, 

 and by uniting with the pure acid to constitute a true fluat* 

 MM. Gay Lussac and 'J henard are of a difl'crent opinion. 

 Thcv sav that the whole of the silcx cannot by this method 

 be removed, but onlv the principal part. Their reason for 

 this belief is, that on tepeatedly evaporating the salt after 

 the addition oi' ammonia and redissolving it, they have each 

 lime observed a residue of siiex. If they employed metallic 

 evaporating vessels, the results of rny experiments do not 

 agree with theirs; for making use of plalina for this pur- 

 pose, and adding an excess of ammonia, I never detected 

 traces of silex on evaporating the filtered fiuat. But our 

 results aoree, if they emjiloytd glass or porcelain vessels, 

 uhich fiuat of ammonia has the property of corroding. 



I now proceed to the consideration of Huat of ammonia j 

 but before I describe some of the properries of this fluat 

 which 1 have observed, I sliall brietly mention the means 

 pursued for ascertaining the proportions of Us constituent 

 parts.'' 



The composition of subsilicated flnat of ammonra being 

 known, that of the fliiat (granting what is already advanced 

 res|>ecting its formation to be correct) may be inferred 

 froni the proportion of silex that a given quantity of am- 

 monia will precipitate. 18 cubic inches of ammoniacal 

 gas were condensed by | of a cubic inch of distilled water 

 in a small glass tube over clean niercury. This ammonia- 

 cal solution was added to a clear filtered solution of sub- 

 s.licated fluat of aintnonia. A precipitate of silex was im- 

 mediately produced. After several hours standing, this 

 precipitate was collected on a filter, well washed, and dried 

 and liealed to redness. It was pure silex, and weighed 

 1-C grains. This experiment, like all the precedmg, was 

 repeated, and the result confirmed. la both instances 

 there was an excess of subsilicated fluat. The precipita- 

 tions were made in a plalina vessel, and the solutions were 

 neither heated before or after the separation of the silex. 

 Calculating from this result, 100 parts of fluat of ammonia 

 Seem to couai»t of J^'i ammonia 

 iJ3 6 fluoric acid 



lUOO 

 Water appears to be a constituent part of this salt. 



It n\.K\ be rendered neutral by means of a gentle heat, 

 which expels the excess of ammonia employed in its for- 

 mation. \n its neutral state, it has a strong saline taste, 

 and it readily deliquesces when exposed to the atmosphere. 



i.ikc 



