OF ARKANSAS Jg£ 



Silica 9.9G8 



Peroxide of iron 3.523 



Oxide of cobalt trace 



Lime 1.833 



Magnesia 0.192 



Water 1.295 



100. 17G 

 The air-dried mineral lost 0.1 per cent, of moisture at 220 deg. F. 

 The free oxygen was determined by Mohr's method. The 1.295 per 

 cent, of water were determined by the loss which the mineral suffered on 

 ignition; the volatile matter was not collected; hence, it remains uncer- 

 tain whether it consisted of water, or of water and oxygen; but if any 

 oxygen had been driven out by heat, it is difficult to conceive why the 

 weight, after repeated ignitions, remained constant, and why not the 

 whole of the oxygen beyond the composition MnO was removed, 

 amounting to 2.328 per cent. For this reason the loss on ignition has 

 been stated as water. 



No. 24. Psilomelane, six miles north of Batesville, on Poke bayou. 



Massive; lustre submetallic; color iron-black; fracture uneven, platy; 

 hardness 5.5; powder reddish-brown. 



Before the blowpipe, infusible; on charcoal in reduction flame, becomes 

 brown; in a matrass, yields a little water; with fluxes gives the manga- 

 nese reactions. 



Dissolves in hydrochloric, acid with evolution of chlorine, leaving a very 

 slight residue of silica. 



The mineral was only partially analyzed. It lost at 250 deg. F. 0.452 

 per cent, of moisture; heated higher, but below redness, the dried mineral 

 lost 1.124 per cent., probably water; and on ignition lost, additionally, 

 5.185 per cent., which must have been oxygen. The free oxygen was 

 determined, after Mohr's method, to be 11.700 per cent. 



The qualitative examination proved the presence of small quantities of 

 cobalt, baryta, lime, magnesia, and silica. 



Commercial value of the Ores of Manganese. 



The ores of manganese are used in the arts principally for the purpose 

 of bleaching, where they serve, in conjunction with common salt and sul- 

 phuric acid, to produce chlorine, the bleaching agent, and in the manufac- 

 ture of glass, for the purpose of correcting the tinge imparted to the glass 

 by iron. In both cases, their value entirely depends on the amount of 



