SOME FEATURES IN THE ANALYSIS OF DOLOMITE 
ROCK. 
BY NICHOLAS KNIGHT. 
The purpose of this work was to compare different 
methods of determining silica in dolomite, and also to 
ascertain the amount of magnesium oxalate that will 
precipitate with calcium oxalate in connection with the 
analysis of dolomite rock by different students. These 
rocks abound in Iowa and in many other portions of the 
United States. The specimens under examination were 
variable mixtures of calcium and magnesium carbonates, 
with silica, ferric oxide and aluminum oxide. All were 
obtained from the Mount Yernon quarry and belonged to 
the Niagara period of geologic history. 
At first a complete analysis of each specimen was made. 
Miss Grace Bradshaw determined the silica by two different 
methods to see how the results might agree. 
1 . A gram of the fine powder was placed in a small beaker, 
and, covered with a watch glass, it was dissolved in pure, 
dilute hydrochloric acid, by gently heating to the boiling 
point. The insoluble residue consisting of silica was fil- 
tered and the amount determined. 
2. A gram of the substance was placed in a porcelain 
evaporating dish, and while covered with a watch glass, 
dilute hydrochloric acid was added. It was warmed on 
the water bath until there was no more evolution of gas. 
( 127 ) 
