102 
IOWA ACADEMY OF SCIENCES. 
tas and with soda lime on the other side. The bend of 
the tube n is filled with water which makes it possible to 
observe the rate of the reaction. 
The absorption tubes k and I are weighed and two or 
three grams of the substance are placed in the decompos- 
ing flask, then the apparatus is tested to learn if all the 
joints are tight. Dilute hydrochloric acid is slowly added 
from c. When the action has ceased, the funnel c is re- 
moved and the tube d is connected with the funnel tube 
a, and a slow current of air is aspirated through the ap- 
paratus, while the flask K is heated until the liquid boils. 
This sweeps the carbon dioxide into the absorption tubes. 
When the apparatus is thoroughly cooled the tubes k and 
I are weighed, the increase representing the amount of 
carbon dioxide in the specimen. Some recommend the use 
of only one soda lime tube, but two ‘make the absorption 
of all the carbon dioxide more certain. 
One of the principal difficulties in connection with this 
method is the possibility of the escape of the carbon di- 
oxide through the numerous rubber connections. Every 
one who has made an ultimate analysis by combustion 
understands how constant a source of error the joints are, 
and how carefully one must guard losses through the walls 
of rubber tubing. 
A much simpler method than the one described was de- 
vised by Bunsen, shown in Fig. 2. This method is not 
usually described in the text-books. A gram of the finely 
pulverized substance is weighed into the flask, d. The 
bulb c is nearly filled with a mixture of one part con- 
centrated hydrochloric acid and three parts water. The 
bulb li contains cotton which assists in condensing the 
vapor. Attached to the bulb is a small tube filled with 
fused calcium chloride. The apparatus from c to e in- 
clusive is carefully weighed. By means of a rubber tube 
attached to the calcium chloride tube e, the dilute acid is 
started into the flask d by suction with the mouth. When 
all the liquid has passed over, the apparatus is held in the 
hand and gently warmed, until the powder is dissolved or 
effervescence ceases. The apparatus is then connected 
