OF ARKANSAS. \ffi 



Chemical constitution of the ores of Manganese. 



The constitution of the manganese-minerals which do not occur in the 

 crystallized state, has been a point of some discussion amongst mineralo- 

 gists. As long as their rational formulae are not indubitably established, 

 every new analysis may be expected to throw some light on the subject. 

 Although the foregoing analyses were principally executed with a view 

 to ascertain the economical value of the ores, the importance of the sub- 

 ject may serve as an excuse, if I take up a short space for purely theoreti- 

 cal speculations. 



It was Rammelsberg, if I mistake not, who first considered psilomelane 

 as a compound of peroxide of manganese with bases of th« constitution 

 RO, these bases being principally MnO, BaO,KO, CaO, MgO, and Co05 

 the peroxide of manganese in these compounds acts the part of the acid. 

 Adopting this view, we have to reject, in the construction of a formula, 

 the silicia and the bases of the constitution R 2 3 , as adventitious constitu- 

 ents; a rejection which, though rather arbitrary,* may be admitted on the 

 a of expediency. Leaving, therefore, the silica in the analysis of Nos. 

 20 and 21 out of consideration, and calculating the'remaining constituents 

 for 100, we obtain for these minerals the following composition: 



No. 20 No. 21 



Protoxide of manganese- • • • 86.898 87.22 



Oxygen 10.718 10.58 



Baryta 0.523 0.29 



Lime trace 1 .27 



Water 1.801 0.G4 



100.000 100.00 



Uniting the free oxygen with a portion of the protoxide of manganese to 

 the formation of peroxide, we have 



For No. 20. 



Peroxide of manganese 58.373 contains O 21.4 



Protoxide of manganese 39.243 " 8.83) 



Baryta 0.523 " 0.05V 9.53 



Water 1.801 " 1.651 



* Compare on this subject the observations of Gustav Bischof, in the 2d vol., ot' his " Ele- 

 ments of chemical and physical geology," p. 85, etc. 



