210 
IOWA ACADEMY OF SCIENCE 
A third specimen of siderite was available for examination, and 
it was subjected to the same treatment as before, with the follow- 
ing results : 
a 
b 
c 
d 
Insoluble residue, per cent 
0.40 
0.36 
0.40 
0.38 
Si0 2 , per cent 
0.36 
0.31 
0.35 
0.32 
DOLOMITE. 
Specimens from Mount Vernon, Iowa: 
a 
b 
0 
d 
1 . 
Insoluble residue, per cent 
0.83 
0.89 
0.88 
0.83 
Si0 2 , per cent 
0.50 
0.64 
0.62 
0.60 
2. 
Insoluble residue, per cent. 
0.54 
0.53 
0.58 
0.56 
Si0 2 , per cent 
0.41 
0.42 
0.41 
0.41 
When the dolomites are treated with nitric acid, it is impossible 
to stir the substance to a dry powder at the temperature of the 
water bath, the large amounts of calcium and magnesium nitrates 
seriously interfering with the drying. 
In the following determinations, a second portion of residue was 
obtained in nearly every case. It was found impossible to dissolve 
the substances in nitric acid, and aqua regia was substituted. 
The results from the different methods are not all concordant. 
HAEMATITE 
a b c 
Residue, per cent 
Residue from filtrate, per cent 
...2.26 
...0.71 
2.52 
0.22 
Aqua Regia 
3.19 
0.00 
Silica from first residue, per cent 
Silica from second residue, per cent 
...1.94 
...0.65 
2.23 
0.22 
Total silica obtained, per cent 
.. ..2.59 
2.45 
.2.90 
MAGNETITE 
Residue, per cent 
Residue from filtrate, per cent 
...5.76 
...0.96 
6.47 
0.30 
11.69 
0.30 
Silica from first residue, per cent 
Silica from second residue, per cent 
...1.44 
...0.96 
2.53 
0.80 
3.09 
0.30 
Total silica, per cent 
...2.40 
2.83 
3.39 
