W. J. Comstock— Chemical Composition of Uraninite. 221 
eral with sulphuric acid in-a sealed tube and titrating with a 
solution of potassium permanganate, thus affording with the 
uranium, lead and iron determined, all necessary data for caleu- 
lation. That this method can be employed with accuracy in 
presence of both UO, and UO, was first proved by experiment- 
ing upon pure U,O,. The best results were obtained by boil- 
ing the sulphuric acid used to expel the air, and displacing the 
air in the tube by CO, before sealing. The following are the 
results obtained. 
Taken. Found. 
1. +5160 U,O, containing - --.-1655 UO, 1647 UO, 
. 06 UO" "60s U0, ‘1599 UO, 
Assuming the state of oxidation in which the lead and iron 
exist in the mineral, the percentages of UO, and UO, can be cal- 
culated from the data furnished by the permanganate titration. 
he most probable assumption is that they exist as PbO and 
FeO, replacing the UO, by equivalent amounts of (PbO), and 
(FeO), The analysis then becomes: 
Ratios 
UO, = 40°08 "1892 "1392 
UO, = 54°51 2004 
PbO = 4°27 (PbO), 0095 2133 
FeO: = ‘i 0084 
“49 (FeO 
88 
Total 100°23 
We shall then obtain the ratio— 
Iv 
RO,: RO,=-2133 :°1892=153 :1=3-06:2 
and the composition of the mineral will be represented by the 
formula— 
3RO,+2R0, 
in which the R represents tetrad uranium replaceable by two 
atoms of lead or iron, and R, hexad uranium. 
_tt is also possible that the iron exists as Fe,O,, which, like 
pitchblende, crystallizes in the isometric system. But under 
that Supposition, the ratio of 8:2 would not be essentially 
changed. 
When the mineral is heated in air, it is to be expected that 
the uranium would be oxidized to the state of U,O,, and the 
ton to Fe,O,. Calculated from the analysis, the gain in weight 
by this oxidation would amount to 1°48 per cent its weight. In 
determining the water, the mineral was found to weigh °67 per 
cent more after ignition; this, added to the water expelled, 
Sives 1°45 per cent. 
Am. Jour. 8c1,—Tuep —_ Vou, XIX, No. 111.—Maron, 1880. 
