ON FLUOR MINERAL 27 



and because he obtained no precipitate, he thinks it fully 

 proved that fluor contains no lime. I maintain, on the 

 contrary, that all solutions of fluor yield a precipitate of 

 gypsum whenever vitriolic acid is added to them. 



Were I to attempt an explication of Mr. Monnet's experi- 

 ment, I should be induced to think that he diluted his 

 solution with too great a quantity of water. But why does 

 he take equal quantities of alkali and fluor, whereas, in my 

 Dissertation on Muor, I say that I took four parts of alkali to 

 one part of fluor ? I likewise mentioned in the same Disserta- 

 tion, that fluor, melted with caustic alkali, undergoes no 

 change. Now, Mr. Monnet undoubtedly knows that alkali, 

 when exposed to a strong fire without fusing, becomes 

 caustic, the very thing which happens in his experiment. 

 The result is quite different if the experiment be made with 

 four parts of alkali ; here the fluor is decomposed by means 

 of a double elective attraction ; and this is the reason that 

 Mr. Monnet obtains pure lime in the filter. Mr. Monnet 

 is further of opinion that fluor may be precipitated by the 

 phlogisticated alkali, because he obtained from its solution a 

 much larger quantity of Prussian blue, though of a paler 

 colour than was to be expected from the small quantity of 

 iron contained in the fluor. Thus we should have, according 

 to Mr. Monnet's idea, a new discovery concerning the con- 

 stituent parts of the fluor, viz, a new metallic earth, quite 

 different from all others, since metallic calxes alone have the 

 property of being precipitated by phlogisticated alkali. If 

 a chemist, however, speaks of the lixivium sanguinis, or 

 phlogisticated alkali, he always understands a lixivium where 

 the alkali does not predominate, but where it is perfectly 

 neutralised ; but of such an alkali Mr. Monnet probably did 

 not make use in this experiment ; for I can affirm with 

 certainty, that phlogisticated alkali does not precipitate the 



