OF ARKANSAS. J(J9 



Protoxide of manganese 10.08 " M ) 



Baryta 2.75 " "V 4.84 1 



Oxide of cobalt 0.15 " ") 



"Water 16.33 " " 14.52 3 



100.72 



This is the same formula which Rammelsberg established for the com- 

 position of the wad from llubeland (v. 2d supplement, p. 167). 



Proceeding in the same manner with the analysis of I\ T o. 22, that is, 

 rejecting silicic acid and peroxide of iron, and calculating the remainder 

 for 100, Ave have: 



Protoxide of manganese ; 8G.9G 



Oxygen 9.20 



Lime 2.12 



Magnesia 0.22 



Water 1 .50 



100.00 

 80.96 parts of protoxide of manganese consist of 67.41 of manganese and 

 19.55 of oxygen; hence we have, in toto 67.41 manganese to 28.75 oxygen, 

 corresponding to the ratio 69.68 Mn : 29.72 O; 

 the compound Mn 2 3 requires 69.68 Mn : 30.42 O, 

 so that the' mineral may be considered as sesquioxide of manganese, or 

 braunite, under the supposition that we are justified in rejecting lime, 

 magnesia, and water as adventitious. But if these bases have to be taken 

 into consideration, and the free oxygen is united with a portion of the 

 protoxide of manganese to the formation of peroxide, we have: 



Peroxide of manganese 50.10 contains O 18.40 



Protoxide of manganese 46.06 " " 10.36^ 



Lime 2.12 << « 0.601 



Magnesia 0.22 " " 0.08 f 



Water 1.50 " " 1.33 J 



Here the oxygen-ratio of RO : MnO 2 is nearly as 4 : 6, which would lead 

 to the formula 



4 (MnO. CaO. MgO. HO). 3 MnO* 



I am not at present prepared to pronounce in favor of any of these 

 views, but as I am continuing" my investigations into the composition of 

 the massive manganese-minerals, I hope to find myself soon enabled to 

 advance some well-founded views on the subject. 



