OF ARKANSAS 165 
SLC aie o o89 8 be eee eee WA ae wd a Fe Oe 9.968 
Peroxide of iron: ++ e+ esse cence eee eneee 3.523 
Oxide of cobalt. . cece ere seer ener eeenee trace 
Ti Gs Ge oe See ASS ee A 1.833 
Magnesia: +.eeerececee near ence Bn Save we 0.192 
Water. % avs seis ewes te Nowe eae we 1.295 
100.176 
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, itis difficult to conceive why the 
weight, after repeated ignitions, remained constant, and why not the 
whole of the oxygen beyond the composition Mn?04 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 
