Calcareous Genus. $$ 



flowly, below ignition, but lofe this property 

 when made red hot, and alfo on cooling. 

 It melts perfe in a ftrong heat, and violently 

 attacks the crucibles, as it powerfully pro- 

 motes the fufion of argillaceous Earths. It 

 is alfo fufible with mineral alkali, borax or mi- 

 crocofmic fait, and without effervefcence. It 

 confifts of the fparry acid, water, and calcareous 

 Earth. According to Mr. U Arcet, the acid 

 is in the proportion of 16 per cent. 22 Roz. 

 24. and according to Mr. Scheelc, 100 gr. of 

 fluor contain about 57 of mere Earth, and 

 confequently about 27 of water ; but I^be- 

 lieve it contains much lefs water, and much 

 more acid, for a great deal of the acid pierces 

 through the luting during diftillation. 



It is decompofed by diftilling it with three 

 times its weight of concentrated vitriolic acid, 

 but to obtain the fparry acid pure, it fhould be 

 diftilled with its own weight of that concentra- 

 ted acid pure and colourlefs, at firftwith a gen- 

 tle, and towards the end with a flrong heat, 

 placing water in the receiver, in the proper-* 

 tion of 10 or 12 times the weight of the 

 fpar. The nitrous and marine acids de- 

 compofe it if dilute, but not when thefe acids 

 are concentrated. 



Blue fluors derive their colour moftly from 



iron, but fometimes from cobalt. 2 Berlin* 



D 2 Befcbaff. 



