62 LABORATORY BACTERIOLOGY 



come into the open bulb. It is then returned. This should 

 be repeated several times. Remove the thumb when the 

 open bulb is full, and the liquid will rush up into the closed 

 branch to fill the space occupied by the CO2 which has been 

 absorbed by the caustic soda. Measure the portion of the 

 tube first occupied with gas and now filled with the liquid. 

 This will indicate the quantity of CO2. The remainder of 

 the gas is H. (There are also traces of other gases.) Its 

 explosive property can be tested by filling the open bulb 

 with water, cover it with the thumb and again bring the gas 

 to the open bulb, hold it close to a flame and remove the 

 thumb. A distinct explosion will be heard. 



The ratio of CO2 to H can be determined from the meas- 

 urements. Thus the total amount of gas = 5 cm. The 

 amount absorbed (CO2) = 2 cm. The remaining gas, or 3 cm., 

 = the H. The ratio of CO2 to H is, therefore, as 2:3 or 

 CO2 : H : : 2 : 3. 



