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



nate was ignited so long as heat occasioned any loss of weight ; 

 there remained 46-741 of oxide of zinc. This oxide was soluble 

 in sulphuric acid, and the resulting sulphate remained white, 

 when the excess of sulphuric acid was expelled by heat. 

 50 parts have thus afforded of 



Oxide of zinc, (III,) . . . 46-741 



Red oxide of manganese, (II,) . 3-032 



Red oxide of iron, (II,) . . . 0-180 



Scales of specular iron, . . . 0-220 



50-173 

 50 grs. of the fine powder had remained in a dessiccated at- 

 mosphere some days, without change of weight. A flask, nearly 

 filled with muriatic acid, in which a slip of pure copper had been 

 boiled half an hour, was closely stopped, after introducing the 

 bright weighed slip with the powder. Placed in a bath at 120° 

 for twelve hours, the powder was dissolved completely. The 

 weighed slip of copper had lost 0-840, indicating the addition of 

 only 0-105 of oxygen ; a weight corresponding nearly to that of 

 the oxygen in the neck of the flask, above the acid fluid. 



The excess of weight, which the analysis has given, is there- 

 fore due to oxidation of the manganese, in a higher degree than 

 that in which it exists in the mineral. The calcined mineral 

 gained 0-275 on 50, besides losing by the first effect of heat 0-125 

 moisture. Considering the oxide of manganese as a protoxide in 

 the mineral, 100 parts contain — 



Oxide of zinc, .... 93-482 



Protoxide of manganese, . . . 5-500 



Peroxide of iron, .... -360 



Scales of specular iron, . . . "440 



99-782 

 I have made several analyses, by different processes, operating 

 on different fragments of this mineral, and when the oxides were 

 perfectly separated from each other, in no instance has the red 

 oxide of manganese exceeded 6-40 in 100 of the weight. 



A. A. Hayes. 



Roxbury Laboratory, November 20, 1844. 



