IOWA ACADEMY OF SCIENCE 
209 
solved in concentrated hydrochloric acid and the iron precipitated 
with ammonia. There was obtained 4.64% of ferric oxide. The 
comparatively large amount of insoluble residue, practically the 
same by both tests, was something of a surprise. The amounts of 
the ferric oxide and silica are not in proportion to form a silicate, 
or at best only a portion is silicate. The remainder seems to be 
iron oxide in such a condition as not to be acted upon readily by 
hydrochloric acid. The next two experiments tend to confirm this 
view. 
(c) Method (a) was repeated except dilute nitric acid (equal 
parts nitric acid of a specific gravity of 1.42 and water) was sub- 
stituted for the hydrochloric acid. This leaves a smaller and 
lighter colored residue than the hydrochloric acid. The insoluble 
residue was 1.34%, which proved to be 1.30% silica. On evaporat- 
ing the filtrate to dryness, a second portion of insoluble residue was 
not obtained. 
(d) Method (b) was repeated, using dilute nitric acid. The 
insoluble residue was 1.30%, the silica 1.28%. No residue ap- 
peared on second evaporation. 
The experiments were repeated, using dilute sulphuric acid. 
The results were unsatisfactory, as the residues obtained were 
abnormally large, confirming the well-known fact that the ores 
of iron are not easily soluble in sulphuric acid. A complete anal- 
ysis of the specimen of ore resulted as follows : 
FeO.. 
Fe 2 0 3 
MnO . 
MgO. , 
CaO. . 
Si0 2 . . 
C0 2 .. 
52.59 
4.20 
3.30 
2.68 
0.82 
1.45 
35.00 
100.04 
2. Another specimen of siderite was examined, and treated by 
each of the four different methods described in the foregoing. The 
following figures were obtained: 
abed 
Residue, per cent 1.33 1.26 0.85 0.94 
Si0 2 , per cent 0.91 0.86 0.80 0.85 
No residue was obtained on evaporating the filtrates in the fore- 
going experiments. 
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