of Mineral Substances. 271 



Silica B a 52.50 



Magnesia — e 12.50 



Lime — b 9 



Alumine — c '-25 



Oxide of iron — d 16.25 



Potassa C 0-50 



98 

 Analysis of Conchoidal Apatite, from Zillerthahl. 

 The specific gravity of this mineral is 3.190. After ignition 

 it becomes colourless, without losing its transparency, or de- 

 crepitating, neither does it lose perceptibly in weight. Sprinkled 

 upon hot coals, it exhibits no phosphorescence. 



Having, by previous trials, ascertained tVie presence of phos- 

 phoric acid and lime, its decomposition was eSected as follows : 



a. 100 grains in powder were digested in muriatic acid, 

 which soon formed a solution, a few particles of talc only re- 

 maining, and weighing 0.75 grain. This loss on the hundred 

 parts was made good by the addition of a similar weight of the 

 pure mineral. 



b. The muriatic solution was nearly saturated with caustic 

 ammonia, solution of oxalic acid was then added as long as it 

 formed a precipitate of oxalate of lime, which was collected, 

 washed, dried, and strongly heated in a platinum crucible ; it 

 was then dissolved in muriatic acid, and thrown down by car- 

 bonate of soda, in the state of carbonate of lime, which weighed, 

 when washed and dried, 91 grains, =50 grains of pure lime. 



c. To separate the phosphoric acid from the liquid, from 

 which the lime had been abstracted by oxalic acid ; it was eva- 

 porated to dryness, and the saline residue gradually ignited in 

 a platinum crucible, during which operation muriate of ammo- 

 nia passed off in white fumes. The remainder, when cold, ap- 

 peared as a vitreous mass, blackened by a portion of charcoal 

 derived from the decomposition of the oxalic acid. It weighed 

 47.5 grains. It was dissolved in boiling water, by which 1 

 grain of finely-divided charcoal was separated. 



d. The acid lirpiid was neutralized with ammonia, which pro- 

 duced some turbiducss, and a precipitate, weighing 7 grains, 



