58 The American Geologist. 
July, 1905 
dish, and while covered with a watch glass, dilute hydrochloric 
acid was added. It was left on the water bath until effervescence 
ceased, the accumulations on the watch glass were rinsed off, and 
the evaporation continued until crystals began to appear. Then 
as the evaporation went forward, the substance was stirred with a 
glass rod until a fine dry powder resulted. This was moistened 
with concentrated hydrochloric acid and left on the water bath for 
a few moments. Dilute hydrochloric acid and water were added and 
after sanding a short time, the insoluble residue was filtered off, 
dried in the air bath, and its weight determined. The insoluble 
residue was obtained three different times by each of the two 
methods, varying the weight of the original amount taken. The 
results were as follows: 
Method 1. 
(a) With one gram substance 0.54 per cent. 
(b) " three grams " 0.56 " " 
(c) " ten " " ,0.55 " 
Method 2. 
(a) With one gram substance 0.65 per cent. 
(b) " three grams " 0.55 " " 
(c) " ten " " 0.55 " 
To determine further the nature of the residue, whether it was 
all silica, or wholly or partly a silicate, it was treated in the 
platinum crucible with a few drops dilute sulphuric acid, and the 
crucible was nearly filled with a dilute solution of hydrofluoric acid. 
It was evaporated on the water bath and the excess of sulphuric 
acid removed with the free flame. 
Residue in Crucible obtained by method 1: 
(a) One gram substance 0.13 per cent. 
(b) Three " " 0.12 " 
(c) Ten " " 0.14 " 
Residue in Crucible obtained by method 2: 
(a) One gram substance 0.13 per cent. 
(b) Three " " 0.12 " 
(c) Ten " " 0.11 " 
A blank test was made using sulphuric and hydrofluoric acid 
in the crucible and evaporating to dryness. No residue was ob- 
tained. 
The residue in the crucible was determined and found to be 
Aluminum and iron sulphate . 08 % 
Calcium sulphate . 058 % 
Magnesium sulphate . 00 
0.138% 
Method 3. To compare the insoluble residue obtained by 
fusion with alkaline carbonate with the amount obtained by the 
foregoing methods. 
A gram of the fine rock powder was thoroughly mixed in the 
