On the Zinc Mines of Franklin, N. J. 261 



to the presence of manganese ; and second, that this metal does 

 not exist as red oxide, (a double oxide consisting of single equiv- 

 alents of protoxide Mn, anddeutoxide Mn,) but simply as prot- 

 oxide. He has shown that the red color is owing to the peroxide 

 of iron, aided, as he believes, by the molecular arrangement of 

 the particles, when the color is in the greatest intensity. 



The various examinations tend to show that the oxides of iron 

 and manganese do not constitute definite atomic proportions in 

 the mineral, but exist in unequal distribution. Its composition is 



therefore to be expressed simply as Zn, mixed with Mn, and Fe. 

 Berthier's results approach very nearly to atomic proportions,* but 

 Berzelius and Rammelsberg, in citing both Berthier's and Bruce's 

 analyses, have given no formula. The formula given by Kobell 

 and Plattner,f who suppose the manganese to exist in the mineral 

 as red oxide, is of course no longer correct. 



Analysis of Red Oxide of Zinc. 



The specimens examined presented masses, made up of par- 

 allel folia, each about one fortieth of an inch in thickness. A 

 slight white coating invested their surfaces in spots ; generally 

 they were covered by a thin covering, composed of minute scales 

 of specular oxide of iron, giving a dark brown color by refracted 

 light. After removing the ferruginous coating, the surfaces ex- 

 hibited a red color. When fractured across the folia, or reduced 

 to a coarse powder, the color was a pure garnet red ; thin portions, 

 being transparent, emitted red light. Not crystalline ; the ar- 

 rangement of the parts was that of a sublimate. The fine pow- 

 der has a light orange yellow color. After carefully expelling 

 air from a mass, its specific gravity was 5-524. 



Water boiled on the powder gives traces of sulphates and hy- 

 drochlorates in minute quantity. Diluted nitric, acetic and sul- 

 phuric acids, dissolve the fine powder, without the aid of heat ; 

 no gas is disengaged, and some minute scales of specular oxide 

 of iron alone remain. These scales remain for some time sus- 

 pended in the diluted solutions, and, besides rendering them tur- 



* See Phillips's Mineralogy, Am. edition, p. 565. 



t Plaitner on the Use of the Blowpipe, trans, by Muspratt, p. 142. 



Vol. xLTiii, No. 2.— Jan .-March, 1845. 34 



