338 Exfractfrom the thin! Volume of 



Exposed to the blow-pipe on coals, it first forms itself 

 into a white opake round ball ; but it afterwards loses its fu- 

 sibility, and resembles earth strongly calcined. The name 

 of cryolite then is not suited to this fossil because it fuses 

 by the blow-pipe like glass, but perhaps because it has some 

 external resemblance to it. Klaproth repeated the analysis 

 of cryolite in the following manner, in order to determine 

 with the greater precision the proportions of the consti- 

 tuent principles of this fossil : he heated to dryness in a 

 platina crucible 100 grains of crvolite in powder with 300 

 grains of sulphuric acid, to effect a complete separation of 

 tlie fluoric acid. The mixture at first boiled up with a 

 disengagement of fluoric acid vapours. The residuum being 

 dissolved in water was precipitated bv evaporation under 

 the form of a soft saline matter, which was easily redis- 

 solved by the addition of a little water. 



2d. M. Klaproth precipitated from the solution, b\- means 

 of caustic ammonia, the alumine, which \\hcn washed and 

 dried weighed 46 grains, and only 24 when afterwards cal- 

 cped. lliis earth, when dissolved bv heat with diluted 

 sulphuric acid, was entirely precipitated by the addition of 

 potash in regidar cr^'stals of alum. 



M. Klaproth neutralised, by means of acetous acid, the 

 solution from \\'hich the alumine had been separated hy 

 ammonia : he poured into it acetiie of barytes ; and the li- 

 quor being filtered and evaporated, he brought the residuum 

 to a red heat in a platina crucil)le. lie tlicn caused it to 

 rcdissolvc, and freed it by the filter from a small (}uantity of 

 carbonaceous matter. Ey evaporation to dryness he ob- 

 tained G2\ grains of ver)' dry carbonate of soda, which con- 

 tained 36 grains of pure soda. Saturated \\ith acetous acid, 

 it wholly crystallized into acetite of soda. 



Deducting from the 100 grains subjected to analysis the 

 weight of the quantities of alumine and soda found in them, 

 we shall have that of the fluoric acid and of the water of 

 crystaUization. 



Ciyolite then is composed of alumine, scda, and fiuoric 

 acid in the following proportion^ : 



Soda - - - - - 3C) 



xVluminc - - - - 2i 



i'luoric acid and water of ervstallizatiou -J s 



loo 



Analijsis of rmhr Laiih hij 1\L Klaproth. 



The old mlneralogi:;-ts gave the nar.ic of umber e.uih to a 



brown 



