262 On the Zinc Mines of Franklin, N. J. 



bid, give a dull brown color ; the filtered solutions are colorless 

 and transparent. The diluted nitric solution, with red prussiate 

 of potash, gives no blue color, while the yellow prussiate produces 

 a blue precipitate, like that of peroxide of iron in a solution of 

 salt of zinc. The addition of carbonate of lime to the nitric so- 

 lution occasions the separation of peroxide of iron, without remo- 

 ving any peroxide of manganese. When hydrochloric acid is 

 used for effecting solution of the powder, the cold acid exhibits a 

 slight yellow tint ; no brown color produced by peroxide of man- 

 ganese appears ; a solution of muriate of ammonia, aided by heat, 

 dissolves the powder, ammonia being disengaged, and the scales 

 of specular oxide of iron form the only residue. 



By heat, the color of the powder becomes darker, and finally 

 brown ; on cooling, the powder becomes of a dull ochre yellow. 

 Acids indicate that a change of composition has resulted from 

 heating ; a separation of peroxide of manganese attending the 

 solution in cold diluted acids. 



These trials prove that the oxide of manganese in this mineral 

 is in the state of protoxide, and that the orange color of the pow- 

 der is probably due to the presence of peroxide of iron, having 

 the same high coloring power which it exhibits in some double 

 salts. The beautiful garnet red color of the mineral is doubtless 

 due to the molecular arrangement of the particles — an effect more 

 strongly marked than it appears in the Siberian red lead ore, but 

 a less considerable change than is exhibited by the biniodide of 

 mercury or the thionurate of lead. 



Solutions of the powder contained oxides of zinc, manganese 

 and iron, with a minute quantity of silica ; no other substances 

 could be detected. 



Analysis. — 50 grs. of the powdered mineral, which had been 

 dried at 150° F., lost at a higher temperature 0-125 of water, 

 containing organic matter. 



50 grs. of the same powder were dissolved in nitric acid, con- 

 tained in a covered vessel ; by evaporation at a low temperature, 

 a saline mass was obtained. Exposed to a gradually increasing 

 temperature, until red hot, a brown colored residue was left, 

 which, when cold, weighed 50-275. Another quantity of nitric 

 acid was evaporated from it, and a higher temperature employed, 

 without changing the weight. The manganese oxide exhibited 

 the action with acids, which characterizes the red oxide state. 



