6 ACCOUNT of a MINERAL 



forbed by water. The water thereby acquires the tafte of wa- 

 ter impregnated with fixed air or carbonic acid, and the pro- 

 perty of precipitating lime-water and of redilTolving the preci- 

 pitate when added to excefs ; from which circumftances I infer, 

 that the elaftic fluid that is difengaged is carbonic acid gas. 



9. To difcover how much of this acid li contains, I diflblved 

 in diluted muriatic acid 960 grains, ufing every precaution to 

 prevent any thing but elaftic fluid from efcaping during the ef- 

 fervefcence. The diminution of weight that took place a- 

 mounted to 290 grains. This correfponds with the refult of fe- 

 veral other experiments made with the fame intention. This 

 fpar confequeatly contains 30.2 per cent, of carbonic acid. 



10. Having premifed thus much with regard to the adion 

 of acids in general on the foflil, and concerning its compofition, 

 I fliall delay mentioning its habitudes with each till I have de- 

 tailed the efFedls of heat upon it. 



11. When heat is applied to the Strontian fpar, it crackles a 

 little, and as the temperature increafes it lofes its tranfparency, 

 becomes white, opaque, and in fome meafure friable. It re- 

 quires, however, a very ftrong fire to produce any further 

 change. 



12. I PUT two pieces, weighing together 320 grains, into a 

 fmall crucible, and inverting another over it, I placed it in an 

 open fire. In this fituation it remained for three hours, the fire 

 being good, and at different times animated by means of bel- 

 lows. Thefe pieces retained their form ; they were white, 

 opaque and brittle, and had loft only two grains of their weight. 

 Their chemical properties were unaltered. 



13. A VERY vehement heat occafions remarkable changes. 

 A fmall mafs was inclofed in a crucible, made of pure Stour- 

 bridge clay, already prepared for forming glafs-houfe pots, ha- 

 ving a lid fitted to it of the fame materials. The crucible, gra- 

 dually heated, was kept for forty-five minutes in the intenfe 

 heat excited by the well managed fire of a fmith's forge. At 



I the 



