8 NEW HAMPSHIRE EXPERIMENT STATION [Bull. 242 



the top of the lamp chimney. In the process of combustion there 

 is considerable absorption of oxygen, and the air inside the circulat- 

 ing system of chimney, bottles and blower decreases in volume. This 

 decrease is compensated by a discharge of oxygen from the spiro- 

 meter into the main air current, and the ultimate effect is a fall in 

 the level of the spirometer bell. This fall (read on a millimeter scale 

 attached to the spirometer) serves as a measure of the volume of 

 oxygen consumed. 



Fig. 1. The oxy-calorhneter for deterviiniiig the energy values 

 of foods and feces. 



A, combustion chamber. B, soda-lime bottles for absorption of 

 carbon dioxide. C, blower to circulate air current. D, spirometer 

 to measure the volume of oxygen used. 



The use of two soda-lime bottles permits complete exhaustion of 

 the reagent in the first bottle. When this is exhausted, the second 

 bottle (i. e., nearest the blower) is substituted for the first; and an- 

 other bottle, containing a fresh supply of soda-lime, is placed next 

 to the blower. The small bottle shown in Fig. 1 directly in front 

 of one of the soda-lime bottles serves as a safety trap during tlie 

 introduction into the spirometer of oxygen from the cylinder of the 

 compressed gas. 



The actual combustion of a food sample in the oxy-calorimeter 

 is carried out as follows: 



