of Mineral Substances. 35 



The mixture was then further diluted with four ounces of water, 

 and the digestion continued at a higher temperature till the 

 residue acquired an uniform gray colour ; the whole was theu 

 poured on a filter. 



c. The nitric solution was concentrated by evaporation and 

 mixed with muriatic acid, which produced no further change 

 than that the original sky-blue colour became green ; the ad- 

 dition of sulphuric acid, however, caused an abundant deposition 

 of sulphate of lead, which being separated, the remaining solution 

 was supersaturated with caustic ammonia, by which the brown 

 oxide of iron was obtained, and after mixture with oil and ig- 

 nition, it afforded 10 grains of magnetic oxide of iron. 



d. The ammoniacal, solution was mixed with sulphuric acid 

 in excess, and a plate of zinc, then immersed, gave 23,5 grains 

 of copper. 



e. The insoluble residue of the ore was boiled in muriatic acid 

 with the addition of a little nitric acid, and this operation was 

 repeated with fresh acid so long as it acted ; the remainder was 

 placed upon a filter and washed, first with very dilute muriatic 

 acid, and then with water. It weighed, when dry, 64 grains ; 

 its sulphur was burned off at a gentle heat, and left 28 grains of ■ 

 incombustible residue ; so that the sulphur consumed amounted 

 to 36 grains. 



f. The remainder, boiled again in muriatic acid, was found to 

 consist entirely of siliceous sand, and weighed 26 grains. 



g. The several muriatic solutions were concentrated by slow 

 evaporation and afforded abundant acicular crystals of muriate 

 of lead ; these were carefully collected, and the evaporation 

 continued as long as they could be obtained ; they were then 

 washed with alcohol acidulated by muriatic acid, dissolved in 

 hot water, and converted by the addition of sulphuric acid into 

 sulphate of lead, the quantity of which, including that separated 

 in process c, amounted to 120.5 grains, equivalent to about 

 85 grains of lead. 



h. The remaining muriatic solution, now free from lead, and 

 which by the test of hydro-sulphuret of ammonia appeared to 

 contain nothing but antimony, was decomposed by a sufficient 

 D 2 



