OF ARKANSAS. 167 
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 formule 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 the constitution 
RO, these bases being principally MnO, BaO, KO, CaO, MgO, and CoO; 
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°O°, as adventitious constitu- 
ents; a rejection which, though rather arbitrary,* may be admitted on the 
plea 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 
Sr ve 
Protoxide of manganese-:.> 86.898 87.22 
OXYZEN rece ee eee eeeeees 10.718 10.58 
Baryta sss esse cece eee eeees 0.523 0.29 
i Fpaaa yee a ae eo ere nee ace trace 1.27 
Walenta ose cue areeseeeed 1.861 0.64. 
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 8.83 
Barytas sere eres cece cece eevee 0.523 ee 0.055 9.53 
Waters sree cece cvecenvcccvveee 1.861 “ 1.65 
* Compare on this subject the observations of Gustav Bischof, in the 2d vol., of his “ Hle- 
ments of chemical and physical geology,’ p. 85, etc. 
