Nov, 1931] FOODS IN A COLLEGE COMMUNITY 9 



apparatus may still be used, and indeed was used by us in our research, 

 by applying a con-ection factor in the calculations, determined by the 

 standardization of the apparatus with a known weight of pure sugar.^ It 

 is far better to avoid the use of this correction factor bj' bringing the 

 whole circulating air sj'stem to the same temperature at the end of the 

 combustion as it was at the beginning. This is done by cooling the soda- 

 lime container either by external application of ice or cold water or by 

 imbedding a copper cooling coil in the soda-lime. 



THE SPIROMETER TYPE OF OXY-CALORIMETER 



The spirometer type of oxy-calorimeter has been more commonly 

 used than any of the other types. It is illustrated in its modified form 

 in Figure 1. The combustion chamber. A. has its base in a brass water 

 seal. The air is withdrawn from the combustion chamber by the blower," 

 C, being conducted from the base of the combustion chamber through 

 the tube, c, by a metal-to-metal contact into a tube leading to the base 

 of the metallic vessel, B, which contains soda-lime. The carbon dioxide 

 is absorbed from the air as it passes up through the soda-lime, and the 

 carbon-dioxide free, oxj'gen-rich air leaves the container through a tube 

 at the top. In this tube a thermometer is inserted, the temperature of 

 which is verj' important. The air withdrawn from the soda-lime con- 

 tainer is returned bj' the blower, C, directly to the combustion chamber. 

 As it returns, it passes by a T-connection leading to the spirometer, S. 

 If external cooling is provided for the metallic vessel, B, the temperature 

 of the thermometer can be controlled at will. The copper can, B. is 

 suspended so that a reservoir of cracked ice or water can be raised under 

 it from below and the can immersed to any desired depth. The top of 

 the can, B, is secured by a stout rubber band, m, which can be easily 

 taken off for removal of soda-lime or for refilling. To aid in suspending 

 the soda-lime can, a lug, L, is soldered at one side. The vessel can be 

 easily suspended by attaching a wire over this lug and around the en- 

 trance tube, or a wide fork fastened to a retort stand can be used for 

 the suspension. After a little experience in adjusting the level of the 

 cold water, the temperature of the thermometer can be rapidlj^ regu- 

 lated with little danger of overcooling. 



The cooling device for the copper can, described above, has made it 

 possible to simplify the tube leading from the combustion chamber. 

 Thus, the metallic U-tube recommended in the original description of 

 the apparatus ma.v be replaced by the straight tube shown in Figure 1, 

 which makes a direct connection with the soda-lime can. After the com- 

 bustion has ceased, the lamp chimnej-. A, and the tube, c, are ver}' hot, 



^In the control tests carried out in the development of the oxy-calorimeter 

 pure sugar from the Bureau of Standards was employed. We have found that 

 practically any form of granulated sugar can be used with equal success. Un- 

 less the sugar is obviously caked with moisture, the amount of water in the 

 sugar will not afifect the results. Drying the sugar in a desiccator overnight is 

 a good precaution. 



"The rate of ventilation is between 20 and 30 liters per minute, controllable 

 by an external resistance in series with the electric blower, or by a pinch 

 clamp on the rubber tube leaving the blower. 



