IOWA ACADEMY OF SCIENCES. 
129 
I. Determinations by C. C. Carhart. 
The specimen was nearly a typical dolomite, containing: 
PER CENT. 
Ca C0 3 
Mg CO 3 .. 
Si 0 2 
Feo 0 3 and Al 2 0 3 
53.78 
44.96 
0.88 
0.38 
100.00 
The small amount of Mg 0 — i. e. the quantity precipitated 
with the calcium was 0.08 per cent. 
Eleven other determinations of this amount resulted as 
follows: 
PER CENT. 
1 
2 
3 
4 
5 
6 
8 . 
9. 
10 . 
11 . 
0.26 
0.16 
0.20 
0.29 
0.31 
0.11 
0.13 
0.11 
0.17 
0.20 
0.14 
This is an average of 0.18 per cent Mg 0 for the twelve 
determinations equivalent to 0.378 per cent Mg C0 3 . The 
amounts obtained are small and indicate that a sufficient 
quantity of ammonium chloride was added after removing 
the silica, and also that the ammonium oxalate was slowly 
added and not in large excess in the precipitation of the 
calcium. The ammonium chloride forms a double salt 
with magnesium which renders the latter less likely to 
precipitate as oxalate. 
II. Determinations by F. E. Welstead. 
A complete analysis of the specimen gave: 
PER CENT. 
Ca CO 3 50.91 
Larger quantity Mg C0 3 , 42.01 
Smaller quantity Mg O = 0.70% = Mg C0 3 1.47 
Si O s 2.08 
Fe 2 0 3 and Al 3 O 0 3.51 
9 
99.98 
