102 SOME PRINCIPLES AND METHODS OF ROCK ANALYSIS, [bull. 176. 
by calcium chloride. Of course arrangement is made for a current of 
C0 2 -free air with which to sweep out the apparatus before and after 
the experiment, and for a slow current during- its continuance. The 
Fig. 15.— Compact form of apparatus for estimation of carbon dioxide. 
results are very accurate and the determination can be quickly car- 
ried out. 
In the preliminary qualitative test for carbon dioxide, it must be 
remembered that while calcite gives off its carbon dioxide on treat 
ment with cold acid, dolomite and siderite do not, and hence warming 
