iog A SYSTEM OF 



working of this ftone may be mixed with the 

 common fait, for the diftillation of the muriatic 

 acid. 



SECT. XCVIL 



The Sixth Order. 



.•♦• 

 The Fluors *, Fluores Mineraks. Suet. Fluff- 



arter. Germ. Fluff-drteri. 



Thefe are commonly called fluxing vitref- 

 cent, or glafs fpars, becaufe mofl part of therri 

 have a fparry form and appearance : they are, 

 however, often met with in an indeterminate 

 figure. 



Thefe are only known in an indurated 

 Hate, and diftinsruifli themfelves from the 

 other earths, by the following characters. 

 i. They are fcarce harder than a calcareous 



fpar, and confequently do not ftrike fire 



with the Heel. 



2. They do not ferment with acids, neither 

 before -nor after calcination, notwithstand- 

 ing a phlogiflon or an alcali had been 

 added in the calcination. 



3. They do not melt by themfelves, but 

 only fplit to pieces when expoied to a 

 fbrong fire f . But, 



4. In mixtures with all other earths, they are 

 very fufible, and efpecially when they are 



* I have adopted the name of Fluors, in Englifh, to this 

 order. D. C. 



f There may, perhaps, be fome fluors that are pretty re- 

 fractory in the fire, fo as not to be melted : however, all 

 thofe which I have tried, have melted pretty eafily by the 

 blow-pipe ; but I have always taken great care in thefe ex- 

 periments,, that they might not fly away befare they were 

 heated through. E. 



blended 



