METHODS FOR THE ESTIMATION OF CARBON DIOX- 
IDE IN MINERALS AND ROCKS. 
BY NICHOLAS KNIGHT. . 
There seems to be two principal methods employed for the 
estimation of carbon dioxide in a mineral or rock; the one 
devised by Fresenius and the other by his rival Bunsen. 
The Fresenius method has been more or less modified by 
different analysts. In its essential features, however, it is 
substantially as follows: The flask K for the decomposi- 
tion of the substance has a capacity of 200 to 300 c.c. The 
flask is closed with a two-hole rubber stopper. The safety 
tube a passes through one hole, and a bulb tube h through 
the other. A funnel is connected with the safety tube at 
a by a rubber tube. Thus the addition of acid can be 
regulated by the pinch cock at o. d and e contain soda 
lime and caustic potash respectively. These are connected 
with the safety tube after the acid has been added and the 
substance in the flask K has been dissolved. The bulb 
tube h serves to condense the steam. 
The first U-tube, /, contains calcium chloride in its 
lower portion and the second tube, g, is filled with granu- 
lar calcium chloride. These tubes remove the moisture. 
To absorb the hydrogen chloride, the tube h contains small 
pieces of pumice stone which have been boiled in a con- 
centrated solution of copper sulphate and afterwards dried 
in the air bath at 250^ to 300"* C. A calcium chloride tube, 
i, is connected with h. The carbon dioxide is absorbed by 
the two U-tubes k and 1. They are 11 cm. long and 12 
mm. in diameter, and are f full of coarse soda lime, the 
remaining space containing calcium chloride. To prevent 
backward diffusion of carbon dioxide or water, the tube w 
is filled with calcium chloride on the side next the appara- 
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