«f Mineral Substances. 33 



of caustic potassa and boiled; when cold, the precipitated 

 oxide was separated by filtration, and the filtered liquor being- 

 neutralized with muriatic acid was mixed whilst boiling hot 

 with carbonate of potassa, a white precipitate was thus formed, 

 which after ignition weighed 6.5 grains. This precipitate be- 

 came yellow when heated, and again white when cold, which 

 seemed like oxide of zinc ; it readily formed a colourless solu- 

 tion with dilute sulphuric acid, and afforded crystals of sulphat 

 of zinc. These Q.5 grains of oxide I consider as equivalent to 

 5 grains of zinc. 



3. Since the long digestion in nitric acid rendered it probable 

 that a portion of the sulphur of the ore had become acidified, 

 the remaining third of the solution was devoted to the determi- 

 nation of its quantity ; it was therefore mixed with muriate of 

 baryta, and the precipitate when collected, washed, dried, and 

 ignited, weighed 66 grains, which I consider as equal to 9.25 

 grains of sulphur. 



d. The yellowish-white insoluble matter, remaining after the 

 action of nitric acid, was digested in muriatic acid ; the solution 

 was of a straw-yellow colour, and the sulphur separated in 

 yellowish flocculi ; it was collected, washed with very dilute 

 muriatic acid, and dried; its weight was then 57.25 grains ; 

 burned upon a hot plate it left 1 grain of residue, which being 

 fused upon charcoal with borax, yielded a globule of copper 

 weighing 0.75 grains. 



e. The muriatic solution, concentrated by gentle evaporation, 

 gave no trace of muriate of lead ; it was divided into 3 equal 

 parts. 



1 . One of these third parts was diluted with ten parts of 

 water, which rendered it turbid, muriatic acid was therefore 

 added so as just to restore transparency ; hydro-sulphuret of 

 ammonia was then dropped in, which gave a precipitate of a 

 pure orange-colour. 



2. The second third of the muriatic solution was largely di- 

 luted with water, and the white precipitate being collected and 

 moderately heated weighed 30 grains. The remaining liquid 

 saturated with carbonate of potassa afTorded a greenish-gray 



Vol. XII. D 



